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Webots User Guide release 8.3.0

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1. init speeds double left_speed 500 double right_speed 500 modify speeds according to obstacles if left_obstacle left_speed 500 right_speed 500 217 218 39 60 61 62 63 64 65 66 67 68 69 70 71 CHAPTER 7 TUTORIALS else if right_obstacle left_speed 500 right_speed 500 write actuators inputs wb_differential_wheels_set_speed left_speed right_speed cleanup the Webots API wb_robot_cleanup return 0 EXIT_SUCCESS 7 5 5 Conclusion Here is a quick summary of the key points you need to understand before going on The controller entry point is the main function like any standard C program No Webots function should be called before the call of the wo_robot_init function The last function to call before leaving the main function is the wo_robot_cleanup function A device is referenced by the name field of its device node The reference of the node can be retrieved thanks to the wo_robot_get_device function Each controller program is executed as a child process of the Webots process A controller process does not share any memory with Webots except the cameras images and it can run on another CPU or CPU core than Webots The controller code is linked with the 1libController dynamic library This library handles the communication between your controller and Webots The section 6 1 explains in more
2. Device Support Webots name Motors Full support motor left right RGB LEDs Full support leds top leds bottom right left LEDs Full support leds buttons led 0 3 leds circle led 0 7 leds prox h led 0 7 leds prox v led 0 1 leds sound leds rc leds temperature red blue IR sensors Full support prox horizontal 0 6 prox ground 0 1 Accelerometer Full support acc Buttons Full support button forward backward left right center Microphone Clap event only through the robot window Speaker Not supported N A Temperature Not supported N A sensor RC device Not supported N A Table 8 5 Thymio II devices Thymio2 prox h 0 distance sensor feedback 4500 4000 3500 3000 Fe 2500 2000 Ta 1500 Te 1000 500 0 pe 0123 45 678 9 10 distance in meters 4 distance sensor feedback Figure 8 9 Proximity sensor response versus distance The Thymio II distance sensor feedback is given on figure 8 9 The calibration was performed using a regular A4 white paper 8 3 2 Connect Aseba to the Thymio II model The default controller of the Thymio I PROTO is the thymio2_demo controller It should be changed to thymio2_aseba to allow the connection to Aseba programming environment However most world files including the Thymio II robot are already configured to use thymio2_ aseba as a controller for the Thymio II robot Technically thymio2_aseba creates a TCP IP server o
3. measure the performance of Webots and log it in the specified lt file path gt file lt steps count gt is an optional integer value that specifies how many steps are analyzed If sysinfo is also set then the system information are printed in the log file The optional worldfile argument specifies the name of a wbt file to open If it is not speci fied Webots attempts to open the most recently opened file The minimize option is used to minimize iconize Webots window on startup This also skips the splash screen and the eventual Welcome Dialog This option can be used to avoid cluttering the screen with windows when automatically launching Webots from scripts Note that Webots PRO does automatically enable the Fast mode when minimize is specified The mode lt mode gt option can be used to start Webots in the specified execution mode The four possible execution modes are pause realtime run and fast they correspond to the simulation control buttons of Webots graphical user interface This option overrides but does not modify the startup mode saved in Webots preferences For example type webots mode pause filename wbt to start Webots in pause mode Note that run and fast modes are only available in Webots PRO The sysinfo option displays misc information about the current system on the standard output stream and quits Webots The stdout and stderr options have the effect of red
4. now merge these two Spheres into only once using the DEF USE mechanism hands on O note Select the first Sphere node the child of the Shape in the scene tree view The field editor of the scene tree view allows you to enter the DEF string Enter BALL GEOMETRY Select the boundingObject field containing the second Sphere node and delete it by using the Reset to default button Then click on the Add button and select the USE gt BALL_GEOMETRY in the dialog box The result is shown in figure 7 5 Now changing the radius field of the first Sphere node does also modify the boundingObject 7 3 7 Add Walls E theory For convenience the boundingObject field accepts also the Shape node rather than the Sphere node directly It would be also possible to use the same DEF USE mechanism at the Shape level as shown in figure 7 6 For now the best advantage is to use this Shape also directly for graphical purposes Later this will turn out to be very useful for some sensors 205 In order to verify your progression implement by yourself four walls to surround the environ ment The walls have to be defined statically to the environment and use as much as possible the DEF USE mechanism at the Shape level rather than at the Geometry level Indeed it s more convenient to add an intermediate Shape node in the boundingOb ject field of the Solid node The best Geometry primitive to implement
5. By default Webots will download the different modules you purchased and store them in the local user application folder e Windows C Users MyName AppData Local Cyberbotics Webots 8 0 e MacOS X Users MyName Library ApplicationSupport Cyberbotics Webots 8 0 e Linux home MyName local share Cyberbotics Webots 8 0 1 6 CLASSROOM LICENSE SETUP 29 You may want to change this behavior and have Webots storing its module files in a different folder This is possible by setting the WEBOTS MODULES PATH environment variable to point to a folder where the modules files will be downloaded and stored It can be useful to do so if you want to avoid that each user has its own copy of the module files In such a case it is recommended for the users to start Webots with the disable modules download option to avoid overwritting files in this folder If you need further information about license issues please send an e mail to lt license cyberbotics com gt 1 6 Classroom license setup This section explains how to setup your Webots licenses to grant access to students in a class room It also explains how to manage student access to Webots licenses for homework Webots exercices or projects Let s assume you purchased 20 licenses of Webots EDU and want to let some of your students use them You should ensure that your classroom machines can access the Internet and in particular the license server of Cyberbotics If it doesn
6. e W Decrease frequency S Increase stride length factor e A Decrease stride length factor nttp birg epfl ch page66584 html 124 CHAPTER 3 SAMPLE WEBOTS APPLICATIONS Chapter 4 Language Setup Webots controllers can be written in C C Java Python or MATLAB This chapter explains how to install the software development kits for the programming language of your choice 4 1 Introduction Webots can execute controllers written in compiled C C Java or interpreted Python MATLAB languages The compilation or interpretation process requires extra software that must usually be installed separately Only when using C C on the Windows platform it is not necessary to install a separate C C compiler on this platform Webots comes with a pre installed and preconfigured copy of the MinGW C C compiler For any other language or platform the soft ware development tools must be installed separately Note that Webots uses very standard tools that may already be present in a standard installation Otherwise the instructions in this chapter will advise you about the installation of your software development tools 4 2 Controller Start up The wbt file contains the name of the controller that needs to be started for each robot The controller name is platform and language independent field for example when a controller name is specified as xyz_controller in the wbt file this does not say anything about the con
7. hands on In order to be able to actuate the wheels add a RotationalMotor to each HingeJoint and set their name fields from wheell to wheel4 These labels will be used to reference the wheels from the controller 7 7 TUTORIAL 6 4 WHEELS ROBOT 227 Other wheels using WHEEL and WHEEL_PH Physics WHEEL PH geometry Cylinder Figure 7 16 Low level representation of the 4 wheels robot 7 7 4 Sensors The last part of the robot modeling is to add the two distance sensors to the robot This can be done by adding two DistanceSensor nodes as direct children of the Robot node Note that the distance sensor acquires its data along the x axis So rotating the distance sensors in order to point their x axis outside the robot is necessary see the figure 7 14 Add the two distance sensors as explained above The distance sensors are at an angle to 0 3 rad with the robot front vector Set their type field to sonar Set their graphical and physical shape to a cube not transformed hands on having a edge of 0 01 m Set their color to blue Set their name field according to the labels of figure 7 14 7 7 5 Controller In the previous tutorials you learnt how to setup a feedback loop and how to read the distance sensor values However actuating the RotationalMotor nodes is new The following note explain how to proceed 228 CHAPTER 7 TUTORIALS To program the rotational moto
8. locked FALSE El translationStep 0 01 rotationStep 0 261799 solid O Node Mass DEF WALL_4 USE count 0 Transform to lt none gt Export Figure 7 7 The simulation state at the end of this second tutorial Add four walls without physics and using only one definition of the Shape node hands on The solution is located in the solution directory under the obstacle wbt 7 3 8 Efficiency The simulation of rigid bodies is computationally expensive The simulation speed can be increased by minimizing the number of bounding objects mini F mizing the constraints between them more information about the constraints Y in the next tutorials and maximizing the dor1dInfo basicTimeStep field On each simulation a trade off has to be found between the simulation speed and the realism theory 7 3 9 Conclusion At the end of this tutorial you are able to create simple environments based on rigid bodies You are able to add nodes from the scene tree view and to modify their fields You have a more precise idea of what are the Solid the Physics the Shape the Sphere and the Box nodes You saw also the DEF USE mechanism that allows to reduce node redundancy of the scene tree 208 CHAPTER 7 TUTORIALS 7 4 Tutorial 3 Appearance 15 minutes The aim of this tutorial is to familiarize yourself with some nodes related to the graphical render ing Good looking simulations can be created v
9. 2 4 1 Selecting an object A single mouse click allows to select a solid object The bounding object of a selected solid is represented by white lines These lines turn rose if the solid is colliding with another one and blue when the solid is idle 1 e it comes to rest and it doesn t interact with any other active solid Selecting a robot enables the Show Robot Window item in the Tools menu Double clicking on a solid object opens the Robot Window and if it was closed the Scene Tree If an object has a solid subpart then it is also possible to select only this subpart by clicking on it once the whole object is already selected or by clicking on it while holding down the Alt key Linux users should also hold down the Control key Ctrl together with the Alt key 48 CHAPTER 2 GETTING STARTED WITH WEBOTS 2 4 2 Navigation in the scene Dragging the mouse while pressing a mouse button moves the camera of the 3D window e Camera rotation In the 3D window press the left button and drag the mouse to select an object and rotate the viewpoint about it If no object is selected the camera rotates about the origin of the world coordinate system e Camera translation In the 3D window press the right button and drag the mouse to trans late the camera with the mouse motion e Zooming Camera rotation In the 3D window press both left and right mouse buttons simultaneously or just the middle button and drag the mouse vertically to zoom in
10. S make S make clean make my_robot class make my_robot o 5 3 2 Windows On Windows you must use the MSYS terminal to compile the controllers MSYS is a UNIX like terminal that can be used to invoke MinGW commands It can be downloaded from http sourceforge net You will also need to add the bin directory of MinGW to your PATH environment variable MinGW is located in the mingw subdirectory of Webots distribution When set correctly the environment variable should be like this WEBOTS_HOME C Program Files Webots PATH C program Files Webots mingw bin C Once MSYS is installed and the environment variables are defined you should be able to compile controllers by invoking mingw32 make in the MSYS terminal e g mingw32 make mingw32 make clean mingw32 make my_robot class mingw32 make my_robot o 5 4 Using Webots Makefiles 5 4 1 What are Makefiles The compilation of Webots C C and Java controllers can be configured in the provided Make files A controller s Makefile is a configuration file used by the make utility and that optionally Inttp sourceforge net 144 CHAPTER 5 DEVELOPMENT ENVIRONMENTS specifies a list of source files and how they will be compiled and linked to create the executable program Note that Python and MATLAB are interpreted languages and therefore they don t need Make files So if you are using any of these programming languages or Visual C then you can igno
11. hpp files It is also necessary to configure the linker to use the Controller lib import library from Webots distribution The Controller lib files is needed to link with the Controller dl11 file that must be used by the controller in order to communicate with Webots The following procedure Visual C 2008 Express explains how to create a Visual C con troller for Webots Note that the resulting exe file must be launched by Webots it cannot be run from Visual C 1 Copy a Webots project from Webots distribution to your Document s folder or create an empty project directory using Webots menu Wizard gt New Project Directory Either way the project directory must contain the cont rollers and worlds subdirectories 2 Start Visual C and select File gt New gt Project Then choose these settings Project type General Template Empty Project Name MyController for example Location C Users MyName Documents MyProject controllers for example Where MyController is the name of a new or already existing controller directory and where Location must indicate the controllers subdirectory of your Webots project directory 3 Then you can add a C or C source file to your project Choose either Project gt Add Existing Item or Project gt Add New Item gt C File cpp In the second case you can copy the content of one of the C C examples of Webots distribution Note that if you copied C
12. 11 2 9 2 PROGRAMMING 267 There is more info on the plugin functions in the Reference Manual in the chapter about Physics Plugins Additional information about the ODE functions can be found here You may also want to study this example distributed with Webots WEBOTS_MODULES_PATH projects samples demos worlds salamander whbt In this example the physics plugin adds user computed forces to the robot body in order to simulate Archimedes and hydrodynamic drag forces 9 2 7 How can I draw in the 3D window There are different techniques depending on what you want to draw 1 If you just want to add some 2d text you can do this by using the function wb_su pervisor set label This will allow you to put 2d overlay text in front of the 3d simulation Please lookup for the Supervisor node in the Reference Manual 2 If you want to add a small sub window in front of the 3d graphics you should consider using the Display node This will allow you to do 2d vector graphics and text This is also useful for example to display processed camera images Please lookup for the Display node in the Reference Manual 3 If you want add 3d graphics to the main window this can be done by using a physics plugin Webots PRO required See how to add a physics plugin in the previous FAQ question just above After you have added the physics plugin you will have to implement the webot s_ physics_draw function The implementa
13. 6 1 Controller Programming lt lt ciar ar a Dee RA A AA OS 155 6 1 1 Hello World Example aoaaa OE eo ee EES Ee SS 155 6 1 2 Reading Sensors os s cacr 28545463 2S 4RS eb Se 244 4 156 Ot USB Actuat rs lt 4 se eseo ma eee EHO eee ew a eS 158 6 1 4 How to use wb robot stepQ escenico rr EES 160 6 1 5 Using Sensors and Actuators Together lt lt 160 14 6 2 6 3 6 4 6 5 6 6 6 7 CONTENTS 6 1 6 Using Controller Arguments v4 bam or A eG 162 6 1 7 Controller Termination lt lt s s e soa e moa a Deot 445442248 4 8 163 6 1 8 Shared libraries ripio 165 6 19 Envitonme t variables s 24 2 3 uor Suk Be Soe ai Boa a Se A 165 6 1 10 Languages settings c soos we oe ee we ee hat e 167 Supervisor Programming lt oos soes moete ewe A okot Bee Re eS 167 G2 A EE By Bnew we od t 168 6 2 2 Tracking the Position of Robots o e 168 6 2 3 Setting the Position of Robots 2 2 5 4 2442442288464 roo 169 Using Numerical Optimization Methods 171 6 3 1 Choosing the correct Supervisor approach 171 62 Resetting Wem 2 2s eda eo ede ek eek e 173 CHIVA Python o age AER a a A Saw ES Rw A 176 641 Class es and Methods A 177 64 2 Controller Class gt ee ek ora sa a Sat Oe ee hee 177 604 3 Chr Exkampl e RR GARA BO AR AA RA A 179 GAL Java Example s se bres reads Be bee o e BE oS 180 645 Python Example 22424454454 424440 434524444 48045 181 Matlab ke et
14. 7 2 3 Create a new Controller We will now program a simple controller that will just make the robot move forwards As there is no obstacle the robot will go forwards for ever Firstly we will create and edit the C controller then we will link it to the robot A controller is a program that defines the behavior of a robot Webots contro llers can be written in the following programming languages C C Java Python Matlab etc Note that C C and Java controllers need to be com piled before they can be run as robot controllers Python and Matlab contro llers are interpreted languages so they will run without being compiled The controller field of a robot specifies which controller is currently linked with to it Please take notice that a controller can be used by several robots but a robot cans use only one controller at a time S theory Each robot controller is executed in a separate child process spawned by Webots Controllers don t share the same address space and they can run in note different processor cores Other languages than C are available but may require a setup Please refer to the language chapter to setup the other languages see chapter 4 note Create a new C controller called e puck_go_forward using the Wizards gt New Robot Controller menu This will create a new e puck_go_forward directory in my_webots_projects tutorials controllers Se lect the option asking you to
15. and from the Tools gt Preferences menu item on the other operating systems 2 6 PREFERENCES 55 The dialog box is separated into tabs Each of the following subsection corresponds to one of this tab 2 6 1 General The General tab contains misc preferences about the application e The Language option allows you to choose the language of Webots user interface restart needed e The Startup mode allows you to choose the state of the simulation when Webots is started pause realtime run fast see the Simulation menu e The Editor font defines the font to be used in Webots text editor and in the Console It is recommended to select a fixed width font for better source code display The default value of this preference is Consolas 10 on Windows Courier 14 on Mac and Monospace on linux e The Number of threads defines how many threads can be created by Webots at maximum The recommended value matches with the number of logical cores of the computer pro cessor It may be interesting to reduce this value in some specific cases for example when another process requires intensively other cores For now this value affects only the phys ical engine speed and the controller compilation speed Note that this is the maximum number of threads allowed but the actual number of threads used is the one defined in the optimalThreadCount field of the WorldInfo node 2 6 2 OpenGL The OpenGL tab contains preferences abou
16. given in the previous section When selecting a specific Bluetooth connection from the popup menu of the control window Webots will try to establish a connection with your e puck robot Once connected it will display the version of the e puck serial communication software on the Webots console e g Running real e puck Version 1 4 3 March 2010 Webots and will switch the control to the real robot That is it will send motor commands to the real robot and display sensor information proximity light camera image etc coming from the real robot This makes the transfer from the simula tion to the real robot trivially simple Note that in the same popup menu the Refresh ports menu item can be used for updating the COM ports The remote control has two requirements the Bluetooth must be correctly set up computer side and the e puck must be programmed with the Webots last firmware For setting up Bluetooth please refer to the official e puck website For uploading the last firmware on your robot switch on your robot press the Upload to e puck robot button on the control window and finally select the select the COM port which corresponds to your robot and the WEBOTS_MODULES_PATH projects robots e puck transfer firmware firmware x x x hex file lo cated in your Webots directory x x x has to be replaced by the current firmware s version Cross compilation An alternative to the remote control session for running the real
17. language Java In the Java case there are two options The controller can be placed in a O Class file or in a jar file Ifa class file is used it must be named xyz_controller class Ifa jar file is used it must be named xyz_ controller jar and it must contain a class named xyz_controller that Webots will attempts to start note 4 3 Using C 4 3 1 Introduction The C API Application Programming Interface is composed of a set of about 200 C functions that can be used in C or C controller code This is the low level interface with the Webots simulator all other APIs are built over the C API A majority of Webots controller examples are written in C therefore the C API is Webots de facto standard API Although less represented in the controller examples the other APIs offer exactly the same functionality as the C API 4 4 USING C 127 4 3 2 C C Compiler Installation Windows Instructions The Windows version of Webots comes with a pre installed copy of the MinGW C C compiler so there is usually no need to install a separate compiler The MinGW compiler is a port of the GNU Compiler Collection gcc on the Windows platform The advantage of using the MinGW compiler will be the better portability of your controller code If you develop your code with MinGW it will be straightforward to recompile it on the other Webots supported platforms Mac OS X and Linux However if you prefer using the Visual C compiler you wil
18. page You will find the description about the ODE functions on this page 9 3 6 Should I specify the mass or the density in the Physics nodes It is more accurate to specify the mass if it is known If you are modeling a real robot it is sometimes possible to find the mass values in the robot s specifications If you specify the den sities Webots will use the volume of each boundingObject multiplied by the density of the corresponding Physics node to compute each mass This may be less accurate because boundingOb jects are often rough approximations 9 3 7 How to get a realisitc and efficient rendering The quality of the rendering depends on the Shapes resolution on the setup of the Materials and on the setup of the Lights The bigger the number of vertices is the slower the simulation is except obviously in fast mode A tradeoff has to be found between these two components To be efficient Shapes should have a reasonable resolution If a rule should be given a Shape shouldn t exceed 1000 vertices Exporting a Shape from a CAD software generates often meshes having a huge reso lution Reducing them to low poly meshes is recommended nttp www cyberbotics com reference chapter6 php Pnttp ode wiki org wiki index php title Manual 9 4 SPEED PERFORMANCE 273 The rendering is also closely related to the Materials To seta Material without texture set only its Appearance node Then you can play with the diffuseCo
19. projects samples curriculum worlds directory These examples are described in the Advanced Programming Exercises of Cyberbotics Robot Curriculum 6 4 C Java Python This section explains the main differences between the C API and the C Java Python APIs Inttp en wikibooks org wiki Cyberbotics _Robot_Curriculum 6 4 C JAVA PY THON 177 Webots binary interface C API implemented in libController C API Java API SWIG generated Figure 6 1 Webots APIs Overview Matlab API Python API SWIG generated 6 4 1 Classes and Methods C Java and Python are object oriented programming languages and therefore the correspond ing Webots APIs are organized in classes The class hierarchy is built on top of the C API and currently contains about 25 classes and 200 methods functions The Java and Python APIs are automatically generated from the C API using SWIG Therefore the class and method names as well as the number of parameters and their types are very similar in these three languages The naming convention of the C Java Python classes and methods directly matches the C API function names For example for this C function double wbh_distance_sensor_get_ value WoDeviceTag tag there will be a matching C Java Python method called get Value located in a class called DistanceSensor Usually the C Java Python methods have the same parameters as their C API counterparts but
20. slowly discharges the robot s battery When the battery level reaches zero the robot is powered off In order to remain powered the robot must recharge its battery at energy chargers Chargers are represented by the semi transparent colored cylinders in the four corners of the arena Only a full charger can recharge the robot s battery The color of a charger changes with its energy level it is red when completely empty and green when completely full 12 CHAPTER 3 SAMPLE WEBOTS APPLICATIONS Figure 3 13 bumper wbt 3 2 2 bumper wbt Keywords TouchSensor bumper DifferentialWheels In this example a robot moves in a closed arena filled with obstacles Its bumper Touch Sensor is used to detect collisions Each time a collision is detected the robot moves back and turns a bit 3 2 WEBOTS DEVICES 73 Figure 3 14 camera wbt 3 2 3 camera wbt Keywords Camera image processing DifferentialWheels In this example a robot uses a camera to detect colored objects The robot analyses the RGB color level of each pixel of the camera images It turns and stops for a few seconds when it has detected something It also prints a message in the Console explaining the type of object it has detected You can move the robot to different parts of the arena using the mouse to see what it is able to detect 74 CHAPTER 3 SAMPLE WEBOTS APPLICATIONS Figure 3 15 connector wbt 3 2 4 connector wbt Keywords Connector Rotati
21. using this command apt key add path to Cyberbotics asc Then proceed to the installation of Webots using apt get install webots This procedure can also be done using any APT front end tool such as the Synaptic Package Manager But only a command line procedure is docu note mented here From the tarball package This section explains how to install Webots from the tarball package having the tar bz2 extension This package can be installed without the root privileges It can be uncompressed anywhere using the tar xjf command line Once uncompressed it is recommended to set the WEBOTS_HOME environment variable to point to the webots directory obtained from the uncompression of the tarball tar xjf webots 8 3 2 1386 tar bz2 or tar xjf webots 8 3 2 x86 64 tar bz2 and export WEBOTS_HOME home username webots Shttp www cyberbotics com linux 26 CHAPTER 1 INSTALLING WEBOTS The export line should however be included in a configuration script like etc profile so that it is set properly for every session Some additional libraries are needed in order to properly run Webots In particular libjpeg62 libav tools libpci and libavcodec extra 54 have to be installed on the system From the DEB package This procedure explains how to install Webots from the DEB package having the deb exten sion On Ubuntu double click on the DEB package file to open it with the Ubuntu Software Center and
22. 7 14 Top view of the 4 wheels robot The grid behind the robot has a dimension of 0 2 x 0 3 m The text labels correspond to the name of the devices 7 7 TUTORIAL 6 4 WHEELS ROBOT 225 The main structure of a robot model is a tree of solid nodes linked together The root node of this tree should be a robot node The solid are linked together by joint nodes A device node should be the direct child of either a robot node theory a a oe either a solid node or a joint node A joint node is used to add one or two degree s of freedom DOF between its parent and its child The direct parent and child of a joint node are both solid nodes Ne The nodes derived from Joint allow to create different kind of constraints Y between the linked solid nodes The most used in robotics is the HingeJoint allowing to model amongst others rotational motors including wheels A joint node can be monitored or actuated by adding respectively a Position Sensor node or a motor node to its device field theory Having these rules in mind we can start to design the node hierarchy used to model the robot The first step is to determine which part of the robot should be modeled as a solid node In our example this operation is quite obvious The robot has 4 DOF corresponding to the wheel motors It can be divided in five solid nodes the body and the four wheels Depending on the expected application of the robot model reducing the numb
23. A EEE 32 A AI 32 26 Preferences A A ew eo Gee ea 54 A AM E 55 202 Ob ocean sie eda tee tee ee te eee ra R 55 27 Citing WEDGES e e scene ah Oh ioe ag aiia AE ai a E e a A E 56 Ze Ciung Cyb rbotes Websites so a OK aa a a a a RY 56 2 7 2 Citing a reference journal paper about Webots 56 3 Sample Webots Applications 59 J Samples AA i E AE E eag Bag ES Be Oe Ga Bee os 59 Sal Dimps WON s p ey a on AR SD ow SS AAA A 60 3142 ganty WO ee eee 6S Rw GDH ESR e AAA 61 319 hexapod WEL ir a ee RA ee Re he RRA A 62 SOA INOW saor SB aoe De Soe Soe eS ew Se Ee AS 63 SA MOOR ee ide ede begun ehee5u45 4394 44 44844444 64 SO POSSE e e he ee ee Be ee Bee bes Bd 65 317 a e es ee a ee ee eK Oe Oa oe See BER Se OSS 66 34 0 FOUND cis soe edu she ede ae 67 3A SOURCE WD sope e 6 ARANA EOS 68 SAAD VAIO WEE ao ek Ye ah ea Be BR eu Oe SoS EER oe HSS 69 3 111 stewart POD os a ee ce oe See A AR oe we G 70 10 CONTENTS Dae Webots Devices Sue abos oe Rose koe a Boao Boe ee See a ee Se OSS 71 32A Dater WOU rr Che Gee ORGS BE OES Be Ode Oe SO S es 71 J22 MUR DOT IV lt iraa koe rr dow e a how Bence rara Weare wie 80 72 Jo COWIE eey hbk eh a hh eG hh ee Gin eg Or ee gad 73 See CONDECION WOE s oe ai ge Bee oh Bee aE ai Tei ee Tena ea a a 74 3 2 3 distance ICAO WH so e s sa ee eee ee RE ew eS 75 326 ai A WEL zess 2 ine atok SO SY AS os Se RS Ee OS 76 3 2 7 NCOders WDE Zac aerea heehee oa A a h oh 11 3 2 9 force o 2c ea de
24. BotStudio ing to your operating system OS Generally it is as simple as using the Bluetooth interface of your OS in order to discover and to pair the e puck as a regular Bluetooth device The complete instructions about pairing can be found on the GCTronic website On linux the pairing has to be done manually without using the Bluetooth interface of the OS This can be done by using the rfcomm command Once generated the rfcomm file has to be given to Webots through an environment variable It may also occur that the rfcomm file doesn t have the read rights A typical pairing can be done using the following commands Get the e puck MAC adress hcitool scan Scanning 10 00 E8 52 BF 32 e puck_1368 Bind the MAC adress of the e puck with a non existing rfcomm file sudo rfcomm bind dev rfcomml 10 00 E8 52 BF 32 Optional Grant the read rights to the rfcomm file sudo chmod 666 dev rfcomml Export the WEBOTS_COM environment variable with between 1 to 9 export WEBOTS_COM1 dev rfcomml Launch Webots webots Bluetooth remote control Once properly set up your Bluetooth connection to your e puck should appear in the popup menu of the control If it doesn t appear there it means that your computer was not properly Shttp www gctronic com doc index php E Puck Getting_started 244 CHAPTER 8 ROBOTS configured to interface with your e puck robot through Bluetooth Please refer to the instructions
25. CONTROLLERS 20 MINUTES 213 feedback loop entry initialise devices exit cleanup read sensors outputs EXIT O step process simulation behavior write actuators inputs Figure 7 10 UML state machine of a simple feedback loop At the beginning of the controller file add the include directives correspond ing to the Robot the DifferentialWheels and the DistanceSensor nodes in order to be able to use the corresponding API documented in chapter 3 of the Reference Manual Nr 1 finclude lt webots robot h gt 2 include lt webots differential_wheels h gt 3 include lt webots distance _sensor h gt Just after the include statements add a macro that defines the duration of each physics step This macro will be used as argument to the wo_robot step function and it will also be used to enable the devices This dura tion is specified in milliseconds and it must be a multiple of the value in the ae basicTimeStep field of the WorldInfo node 1 define TIME_STEP 64 The function called main is where the controller program starts execu tion The arguments passed to main are given by the controllerArgs field of the Robot node The Webots API has to be initialized using the wo_ theory robot_init function and it has to be cleaned up using the wo_robot_ cleanup function 214 CHAPTER 7 TUTORIALS Write the prototype of the main function as fo
26. Chapter 6 Programming Fundamentals This chapter introduces the basic concepts of programming with Webots Webots controllers can be written in C C Java Python or MATLAB Besides their syntactic differences all these languages share the same low level implementation As long as the sequence of function method calls does not vary every programming language will yield exactly the same simulation results Hence the concepts explained here with C examples also apply to C Java Python Matlab 6 1 Controller Programming The programming examples provided here are in C but same concepts apply to C Java Python Matlab 6 1 1 Hello World Example The tradition in computer science is to start with a Hello World example So here is a Hello World example for a Webots controller 1 finclude lt webots robot h gt 2 include lt stdio h gt 3 4 lint main 5 wb_robot_init 6 7 while 1 8 printf Hello World n 9 wb_robot_step 32 10 11 12 return 0 13 155 156 CHAPTER 6 PROGRAMMING FUNDAMENTALS This code repeatedly prints Hello World to the standard output stream which is redi rected to Webots console The standard output and error streams are automatically redirected to Webots console for all Webots supported languages Webots C API Application Programming Interface is provided by regular C header files These header files must be included using statements like inclu
27. Ee ee Be eS 105 33 AA SPINOR Wot osito e 106 ER IN 107 EA E 108 SUF khepera3 WDt 2200258 iii dre 109 33 18 Khepera kinematic BL lt o sci aina ra rr a oe 110 55 19 EREPSTA PRE ROBLE BER SES Da SERS EES 111 3 5 20 Khepera prippercamer wht 24 26 21544404448 0R ee Gee oe 112 33 21 khepera AAA 6 aos iaci iiini heh ee Gh ee ae Whe oes 113 Dee khepera PPE Wot ee oS Be oS BO SO Bd SH oe EH 114 30 23 Kheperatepipwht ios io iris ola 4S44 e 4824 115 3324A TIO e ecos og ae ah ha eh he ee Ye de ee me Bede Stee 116 Jac Marelan WBU e ea eee eR eS Eee ee ee ee Ee 117 3020 ploncerZ wht ociosa EERE RA RS Oa Ks 118 JDL ICE nea de mae a 8 6 8 GO a 2 eA eh 119 die SCOWL WDE eos rs Yea eee Eee ee Ree oS 120 33 29 o eee koe eae Re oe Re em Loe Se a ae ka ee Bowe S 121 E 4 4 464 9645 44 0 64 9 4 oe eR EMRE eon 122 4 Language Setup 125 Al OUCH 2 es Sed es ee eK eee Kk Se owe PSE EEE ESR 125 4 2 Controller Start up os 4444446534 484 Go REESE REE RR OES 125 Aa NN xs ae Hitt we Hot he Pe RR A RL HOG He OHARA BA EO 126 1S WOOO o x ene eek eee ee he bee eee bee ou eee 126 12 CONTENTS SA Usna Ce 2 264 bow koe oe Mew he e oe oem ee See ee Be OS 127 AAT Introduction lt s e e msa aae mas EH eK NEM ARA 127 4 4 2 C Compiler Installation o oeoa 128 4 4 3 Source Code of the Lac API 2 oos e ocs a e asok a ack aooi aia aa 128 43 Usine Java soe A Ge REIR A RH OE DM Ne AS 128 43514 Introduction ei Ob eee EERE AA EEL EES 1
28. Further information about how to export a node are available here e Delete Deletes the selected object 2 4 THE 3D WINDOW 47 Y PP 0 00 38 784 1 02x Figure 2 2 Speedometer 2 3 11 Speedometer and Virtual Time A speedometer see figure 2 2 indicates the speed of the simulation on your computer It is displayed on the main toolbar and indicates how fast the simulation runs compared to real time In other words it represents the speed of the virtual time If the value of the speedometer is 2 it means that your computer simulation is running twice as fast as the corresponding real robots would This information is valid both in Run mode and Fast mode To the left of the speedometer the virtual time is displayed using following format H MM SS MMM where H is the number of hours may be several digits MM is the number of minutes SS is the number of seconds and MMM is the number of milliseconds see figure 2 2 If the speedometer value is greater than one the virtual time is progressing faster than real time The basic time step for simulation can be set in the basicTimeStep field of the WorldInfo node in the scene tree window It is expressed in virtual time milliseconds The value of this time step defines the length of the time step executed during the Step mode This step is multiplied by the displayRefresh field of the same WorldInfo node to define how frequently the display is refreshed 2 4 The 3D Window
29. GCC compiler system Simulation Webots EDU or PRO facilitates the programming of e puck with a powerful simulation remote control and cross compilation system Table 8 1 e puck features of the devices the plane Ox being oriented counter clockwise Note that the proximity sensors and the light sensors are actually the same devices of the real robot used in a different mode so their direction coincide Proximity sensors responses are simulated in accordance with the lookup table in figure 8 3 this table is the outcome of calibration performed on the real robot The resolution of the camera was limited to 52x39 pixels as this is the maximum rectangular image with a 4 3 ratio which can be obtained from the remote control interface with the real robot The standard model of the e puck is provided in the E puck proto PROTO file which is located in the WEBOTS_MODULES_PATH projects robots e puck protos direc tory of the Webots distribution see also E puckDistanceSensor proto PROTO file and E puckGroundSensors proto PROTO file you will find complete specifications in it The two PROTO fields groundSensorSlot and turretSlot have been included in the simulation model in order to support extension modules Several simulation examples are located in the WEBOTS_MODULES_PATH projects robots e puck worlds directory of the Webots distribution The e puck_line wbt world see figure 8 5 especially examplifies the use of ground senso
30. Koala keyboard texture In this example two Koala robots K Team circle on a moon like surface You can modify their trajectories with the arrow keys on your keyboard The moon like scenery is made of IndexedFaceSet nodes Both robots use the same controller code 3 1 SAMPLES 65 Figure 3 6 ghostdog wbt 3 1 6 ghostdog wbt Keywords Quadruped legged robot dog robot passive joint spring and damper This example shows a galloping quadruped robot made of active hip joints and passive knee joints using spring and dampers The keyboard can be used to control the robot s direction and to change the amplitude of the galloping motion Each knee is built of two embedded HingeJoint nodes one active and one passive sharing the same rotation axis The passive HingeJoint simu lates the spring and damping The active HingeJoint is not actuated in this demo but it could be used for controlling the knee joints 66 CHAPTER 3 SAMPLE WEBOTS APPLICATIONS Figure 3 7 salamander wbt 3 1 7 salamander wbt Keywords Salamander robot swimming robot amphibious robot legged robot physics plugin buoyancy A salamander shaped robot walks down a slope and reaches a pool where it starts to swim The controller uses two different types of locomotion it walks on the ground and swims in the water This demo simulates propulsive forces caused by the undulations of the body and the resistance caused by the robot s shape In addition the
31. Mac OS X is a registered trademark of Apple Inc Mindstorms and LEGO are registered trademarks of the LEGO group IPR is a registered trademark of Neuronics AG Ubuntu is a registered trademark of Canonical Ltd Visual C Windows Windows NT Windows 2000 Windows XP Windows Vista Windows 7 and Windows 8 are registered trademarks of Microsoft Corp UNIX is a registered trademark licensed exclusively by X Open Company Ltd Foreword Webots is a three dimensional mobile robot simulator It was originally developed as a research tool for investigating various control algorithms in mobile robotics This user guide will get you started using Webots However the reader is expected to have a minimal knowledge in mobile robotics in C C Java Python or MATLAB programming and in VRML97 Virtual Reality Modeling Language Webots 8 features a new layout of the user interface with many facilities integrated such as a source code editor motion editor etc We hope that you will enjoy working with Webots 8 Thanks Cyberbotics is grateful to all the people who contributed to the development of Webots Webots sample applications the Webots User Guide the Webots Reference Manual and the Webots web site including Stefania Pedrazzi David Mansolino Yvan Bourquin Fabien Rohrer Jean Christophe Fillion Robin Jordi Porta Emanuele Ornella Yuri Lopez de Meneses S bastien Hugues Auke Jan Ispeert Jonas
32. TUTORIAL 1 YOUR FIRST SIMULATION IN WEBOTS 20 MINUTES 197 Webots nodes stored in world files are organized in a tree structure called the scene tree The scene tree can be viewed in two subwindows of the main Ne window the 3D view at the center of the main window is the 3D represen J tation of the scene tree and the scene tree view on the left is the hierarchical h eek aa representation of the scene tree The scene tree view is where the nodes and the fields can be modified In the 3D view click on the floor to selected it When it is selected the floor is surrounded by white lines and the corresponding node is selected in the scene hands on tree view Now click on the blue sky to unselect the floor 7 2 2 Add an e puck Robot The e puck is a small robot having differential wheels 10 LEDs and several sensors including 8 distance sensors and a camera In this tutorial we are only interested in using its wheels We will learn how to use some other e puck features in the other tutorials Now we are going to add an e puck model to the world Make sure that the simulation is paused and that the virtual time elapsed is 0 When a Webots world is modified with the intention of being saved it is funda mental that the simulation is first paused and reverted to its initial state i e the virtual time counter on the 3D view toolbar should show 0 00 00 000 Otherwise at each save the position of each 3D objects can ac
33. WbFieldRef trans2 wb_supervisor_node_get_field robot2 translation detect collision if are_colliding transl trans2 3 In the physics plugin Webots PRO required you can replace or extend Webots colli sion detection mechanism This is an advanced technique that requires knowledge of the 9 3 MODELING 269 ODE Open Dynamics Engine API Your collision detection mechanism must be imple mented in the webots_physics_collide function This function is described in the Physics Plugin chapter of the Reference Manual 9 2 10 Why does my camera window stay black The content of the camera windows will appear only after all the following steps have been completed 1 The Camera s name field has been specified 2 The WoDeviceTag for the Camera has been found with the function wo_robot_get_ device 3 The Camera has been enabled using the function wo_camera enable 4 The function wo camera_get_image or wo_camera_get_range_image for a range finder Camera has been called 5 At least one wo_robot_step or equivalent function has been called 9 3 Modeling 9 3 1 My robot simulation explodes what should I do The explosion is usually caused by inappropriate values passed to the physics engine ODE There are many things you can be try to improve the stability of the simulation adapted from ODE s User Guide 1 Reduce the value of WorldInfo basicTimeStep This will al
34. can see the E puck robot following a black line drawn on the ground In the middle of this line there is an obstacle which the robot is unable to avoid This example has been developed as a practical assignment on behavior based robotics When completed the controller should allow the E puck robot to avoid this obstacle and recover its path afterwards A solution for this assignment is shown in the world e puck_line_demo wbt see subsection 3 5 7 The source code for this controller is in the e puck_line directory 3 5 REAL ROBOTS 99 Webots Figure 3 39 e puck_line_demo wbt 3 5 7 e puck_line_demo wbt Keywords DifferentialWheels line following texture behavior based robotics E puck This example is the solution for the assignment given in the e puck_line_demo whbt ex ample see subsection 3 5 6 In this case you can see that the robot avoids the obstacle then recovers its path along the line As the controller used in this world is the solution to the assign ment the source code is not distributed 100 CHAPTER 3 SAMPLE WEBOTS APPLICATIONS Figure 3 40 hemisson_cross_compilation wbt 3 5 8 hemisson_cross_compilation wbt Keywords DifferentialWheels Pen cross compilation texture Hemisson In this example a Hemisson robot moves on a white floor while avoiding the obstacles Its Pen device draws a black line which slowly fades This example is a cross compilation example for the real Hemisson robot The source
35. charger and a bone 3 5 REAL ROBOTS 95 Figure 3 35 alice wbt 3 5 3 alice wbt Keywords Alice Braitenberg DistanceSensor In this example you can see an Alice robot moving inside an arena while avoiding the walls Its world file is in the others worlds directory Like many others this example uses the braitenberg controller 96 CHAPTER 3 SAMPLE WEBOTS APPLICATIONS 3 5 4 boebot wbt Figure 3 36 boebot wbt Keywords BoeBot DistanceSensor LED In this example BoeBot moves inside an arena while avoiding the walls When the robot detects an obstacle with one of its DistanceSensors it turns the corresponding LE D on 3 5 REAL ROBOTS 97 Figure 3 37 e puck wbt 3 5 5 e puck wbt Keywords DifferentialWheels texture Braitenberg Accelerometer Odometry E puck In this example you can see the e puck robot avoiding obstacles inside an arena by using the Braitenberg technique The odometry of the e puck is computed at each simulation steps The accelerometer values and an estimation the coverage distance and the orientation of the e puck are displayed The source code for this controller is in the WEBOTS_MODULES_PATH projects default controllers braitenberg directory 98 CHAPTER 3 SAMPLE WEBOTS APPLICATIONS Webots Figure 3 38 e puck_line wbt 3 5 6 e puck_line wbt Keywords DifferentialWheels line following texture behavior based robotics E puck In this example you
36. code for this controller is in the hemisson directory 3 5 REAL ROBOTS 101 Webots Figure 3 41 hoap2_sumo wbt 3 5 9 hoap2_sumo wbt Keywords Robot node humanoid texture dancing Hoap 2 IndexedFaceSet RotationalMotor active joint force TouchSensor In this example a Hoap2 robot from Fujitsu performs the Shiko dance the dance which sumos perform before a match This robot is equipped with TouchSensors on the soles of its feet it measures and logs the pressure exerted by its body on the ground The source code for this controller is in the hoap2 directory 102 CHAPTER 3 SAMPLE WEBOTS APPLICATIONS Figure 3 42 hoap2_walk wbt 3 5 10 hoap2_walk wbt Keywords Robot node humanoid texture walking Hoap 2 IndexedFaceSet RotationalMotor active joint force TouchSensor In this example a Hoap2 robot from Fujitsu walks straight forward on a tatami This robot is equipped with TouchSensors on the soles of its feet it measures and logs the pressure exerted by its body on the ground The source code for this controller is in the hoap2 directory 3 5 REAL ROBOTS 103 Figure 3 43 ipr_collaboration wbt 3 5 11 ipr_collaboration wbt Keywords Robot node robotic arm collaboration TCP IP client program IPR IndexedFace Set RotationalMotor active joint In this example two IPR robots from Neuronics work together to put three red cubes into a basket which is on the opposite side of the world All th
37. have a high speed network or use small resolution camera images or compress the image data before sending it to the controller This overhead is negligible if you use a low resolution camera such as the Khepera K213 see example WEBOTS_MODULES_ PATH projects robots khepera kheperal worlds khepera_k213 wbt Chapter 5 Development Environments This chapter indicates how to use the built in development environment or third party environ ments for developing Webots controllers 5 1 Webots Built in Editor Webots source code editor is a multi tab text editor specially adapted for developing Webots con trollers It is usually recommended to use this editor as it makes the compilation straightforward The editor features syntax highlighting for Webots supported language C C Java Python and MATLAB and auto completion for Webots C API 5 1 1 Compiling with the Source Code Editor The Source Code Editor can be used to compile C C or Java source files into binary executable or bytecode Java files that can be executed in a simulation The compilation output is printed to Webots console errors and warnings appear in red If you double click an error message Webots will highlight the corresponding source line in the editor Note that for compiling source code it is necessary to have the appropriate development tools installed You will find information on the development tools here In the following the possible compilation actio
38. include lt webots Robot hpp gt 2 include lt webots LED hpp gt 3 include lt webots DistanceSensor hpp gt 4 5 lusing namespace webots 6 7 define TIME STEP 32 8 9 class MyRobot public Robot 10 private 11 LED xled 12 DistanceSensor distanceSensor 13 14 public 15 MyRobot Robot 16 led getLED ledName 17 distanceSensor getDistanceSensor distanceSensorName 18 distanceSensor gt enable TIME_STEP 19 20 21 virtual MyRobot 22 Enter here exit cleanup code 23 24 25 void run 26 Main control loop 27 while step TIME_STEP 1 28 Read the sensors 29 double val distanceSensor gt getValue 30 l Process sensor data here 32 33 Enter here functions to send actuator commands 34 led gt set 1 35 36 37 38 39 int main int argc char x argv 180 40 41 42 43 CHAPTER 6 PROGRAMMING FUNDAMENTALS MyRobot x robot new MyRobot robot gt run delete robot return 0 6 4 4 Java Example OANNNFWN FR import com public class MyRobot extends Robot private LED led private DistanceSensor distanceSensor private static final int TIME_STEP 32 milliseconds public MyRobot super led getLED my_led distanceSensor getDistanceSensor my_distance_sensor distanceSensor enable TIME_STEP public void run main control loop while Read th
39. includes support for the differential wheel motors encoders are also simulated the infra red sensors for proximity and light measurements the accelerometer the camera the 8 surrounding LEDs the body and front LEDs the other e puck devices are not yet simulated in the current model Besides standard e puck devices the model also provides two slots that can be used to extend the functionality and to equip the robot with additional devices In particular the ground sensors module extension of the real e puck robot is modeled in Webots to provide 3 optional infra red sensors pointing to the ground in front of the robot The table 8 2 displays the names of the simulated devices which are to be used as an argument of the function wb_robot_get_device see the Robot section of Reference Manual The e puck dimensions and speed specifications are shown in table 8 3 The functions wb_ differential wheels set_speed wb differential wheels get left en coder and wo_differential_wheels_get_right_encoder will allow you to set the speed of the robot and to use its encoders As is the case for any Differential Wheels robot set at its default position in Webots the forward direction of the e puck is given by the negative z axis of the world coordinates This is also the direction the eye of the camera is looking to in keeping with the VRML standard the direction vector of the camera is pointing in the opposite direction namely the di
40. is 20 degrees except for the four side sen sors so0 so7 so8 and so15 for which the angle is 40 degrees 8 4 2 Pioneer 3 DX In this section you will learn how to use Webots simulation model of the Pioneer 3 DX robot figure 8 18 Overview of the robot The base Pioneer 3 DX platform is assembled with motors featuring 500 tick encoders 19 cm wheels tough aluminum body 8 forward facing ultrasonic sonar sensors 8 optional real facing sonar 1 2 or 3 hot swappable batteries and a complete software development kit The base Pioneer 3 DX platform can reach speeds of 1 6 meters per second and carry a payload of up to 23 kg The Pioneer 3 DX robot is an all purpose base used for research and applications involving mapping teleoperation localization monitoring reconnaissance and other behaviors Pioneer 3 DX is provided with a ready to use set of devices listed in table 8 7 8 4 USING THE PIONEER 3 AT AND PIONEER 3 DX ROBOTS 257 Figure 8 18 Pioneer 3 DX an all purpose base used for research and applications Feature Description Dimensions 455 mm long 381 mm large 237 mm high Weight 9 kg operating playload of 17 kg Batteries 8 10 hours 3 lead acid batteries of 7 2 Ah each 12 V Microcontroller 32 digital inputs 8 digital outputs 8 analog inputs 3 serial extension ports I O Skid steering drive Turn radius 0 cm swing radius 26 7 cm max traversable grade 25 Speed Max forward b
41. is a DifferentialWheel node and can be access by the webots differential_wheel h include file The speed is given in a number of tick s seconds where 1000 ticks correspond to a complete rotation of the wheel The values are clamped between 1000 and 1000 212 CHAPTER 7 TUTORIALS ps5 ps2 _ ps3 Figure 7 9 Top view of the e puck model The green arrow indicates the front of the robot The red lines represent the directions of the infrared distance sensors The string labels corresponds to the distance sensor names The controller API is the programming interface that gives you access to the simulated sensors and actuators of the robot For example including the webots distance_sensor h file allows to use the wo_distance_ y 7 sensor_x functions and with these functions you can query the values of theory the DistanceSensor nodes The documentation on the API functions can be found in Chapter 3 of the Reference Manual together with the description of each node 7 5 3 Program a Controller We would like to program a very simple collision avoidance behavior You will program the robot to go forwards until an obstacle is detected by the front distance sensors and then to turn towards the obstacle free direction For doing that we will use the simple feedback loop depicted in the UML state machine in figure 7 10 The complete code of this controller is given in the next subsection 7 5 TUTORIAL 4 MORE ABOUT
42. knowledge of the C C Java Python or Matlab programming language is nec essary to program your own robot controllers However even if you don t know these languages you can still program the e puck and Hemisson robots using a simple graphical programming language called BotStudio e If you don t want to use existing robot models provided within Webots and would like to create your own robot models or add special objects in the simulated environments you will need a basic knowledge of 3D computer graphics and VRML97 description language That will allow you to create 3D models in Webots or import them from 3D modelling software 2 1 4 Webots simulation A Webots simulation is composed of following items 1 A Webots world file wbt that defines one or several robots and their environment The wbt file does sometimes depend on external PROTO files proto and textures 2 One or several controller programs for the above robots in C C Java Python Matlab 3 An optional physics plugin that can be used to modify Webots regular physics behavior in C C http www robotstadium org http www ratslife org 2 1 INTRODUCTION TO WEBOTS 35 2 1 5 What is a world A world in Webots is a 3D description of the properties of robots and of their environment It contains a description of every object position orientation geometry appearance like color or brightness physical properties type of object etc Wor
43. libraries 8 2 USING THE NAO ROBOT 247 gt default Drag and drop them in central view Then connect the global onStart input to the Sit Down box s onStart input and the output of this box to the Stand Up box s onStart input Now make sure the simulation is running and push the Play button in Choregraphe This will make the robot sit down and then stand up once he is done sitting down 8 2 5 Using the cameras Webots simulates Nao s top and bottom cameras Using Aldebaran s Choregraphe or the Monitor programs it is possible to switch between these cameras In Choregraphe use the Select Cam era box in Box Library gt Vision The simulated camera image can be viewed in Choregraphe View gt Video monitor The resolution of the image capture can be changed in Webots using the cameraWidth and cameraHeight fields of the robot Note that the simulation speed de creases as the resolution increases It is possible to hide the camera viewports purple frame in Webots by setting the cameraPixelSize field to 0 It is also possible to completely switch off the simulation of the cameras by adding the nocam option before the NAOqi port number in the controllerArgs field e g nocam 9559 8 2 6 Using Several Nao robots It is possible to have several Nao robots in your simulation however each Nao robot must use a different NAOqi port Here how to copy a Nao and assign the NAOqi port number 1
44. of the controller library the location of the current controller directory and the content of the CLASSPATH environment variable In order to include third party jar files you should define or modify this environment variable before running Webots see the previous section in order to know how to set an environment variable Under windows the CLASSPATH seems like this set CLASSPATH C Program Filesijavaljdk1bin relativelmylib jar while under Linux and Mac OS X it seems like this export CLASSPATH usr lib jvm java bin relative mylib jar 4 5 4 Source Code of the Java API The source code of the Java API is available in the Webots release You may be interested in looking through the directory containing the Java files resources languages java SWIG_generated_files in order to get the precise definition of every classes and functions although these files have been generated by SWIG and are difficult to read 4 6 USING PYTHON 131 For users who want to use a third party development environment it can be useful to know that the package of the Java API Controller jar is located in the 1ib directory Advanced users may want to modify the Java API They will need to modify the SWIG script controller i the java sources and the Makefile located in the resources languages java directory 4 6 Using Python 4 6 1 Introduction The Python API has been generated from the C API by using SWIG That implies that their c
45. simulated object If the simulation uses physics vs kinematics then the simulation step also specifies the interval between two computations of the forces and torques that need to be applied to the simulated rigid bodies The execution of a simulation step is an atomic operation it cannot be interrupted Hence a sensor measurement or a motor actuation can only take place between two simulation steps For that reason the control step specified with each wo_robot_step must be a multiple of the simulation step So for example if the simulation step is 16 ms then the control step argument passed to wo_robot_step can be 16 32 64 128 etc 6 1 5 Using Sensors and Actuators Together Webots and each robot controller are executed in separate processes For example if a simulation involves two robots there will be three processes in total one for Webots and two for the two robots Each controller process exchanges sensors and actuators data with the Webots process during the calls to wo_robot_step So for example wo_motor_set_position does not immediately send the data to Webots Instead it stores the data locally and the data are effectively sent when wb_robot_step is called For that reason the following code snippet is a bad example Clearly the value specified with the first call to wo_motor_set_position will be overwritten by the second call 1 wb_motor_set_position my_leg 0 34 BAD ignored 2 wb_motor_set_posi
46. simulation speed is around 1 0x When Webots simulation speed drifts away from 1 0x the physics simulation gets wrong unnatural and thus Choregraphe motions don t work as expected any more For example if Webots indicates 0 5x this means that it is only able to simulate at half real time the motion provided by Choregraphe the physics simulation is too slow Therefore it is important to keep the simulation speed as much as possible close to 1 0x There are currently no means of synchronizing Webots and Choregraphe but this problem will be addressed in a future release It is often possible to prevent the simulation speed from going below 1 0x by keeping the CPU and GPU load as low as possible There are several ways to do that here are the most effective ones e Switch off the simulation of the Nao cameras with the nocam option as mentioned above e Increase the value of Worl dInfo displayRefesh in the Scene Tree e Switch off the rendering of the shadows change to FALSE the cast Shadows field of each light source in the Scene Tree e Reduce the dimensions of the 3D view in Webots by manually resizing the GUI compo nents e Remove unnecessary objects from the simulation in particular objects with physics 8 2 8 Known Problems If for some unexpected reason Webots crashes it is possible that the hal or naoqi bin pro cesses remain active in memory In this case we recommend you to terminate these processes manually before r
47. t work you may need to configure your local firewall to allow Webots to access this URL 1 6 1 User account There are two methods to handle student access to Webots licenses a single user account or multiple user accounts Single user account The single user account method is simpler to setup as you don t need to know the e mail ad dresses of the students Nevertheless you need to setup an e mail address for a generic user for which you can read the e mails received It could be your own personal e mail address Let s call this e mail address webots my university edu A drawback to this method is that it allows a single student to use simultaneously several instances of your 20 licenses possibly all of them thus preventing other students to use them 1 Log in to your Webots user account using your license administration credentials e g the user account which was used to activate your Webots licenses 2 Create a new user pack from the administration page and call it Students 3 Grant access to all your 20 Webots EDU license tick boxes https www cyberbotics com license 30 CHAPTER 1 INSTALLING WEBOTS Set the concurrency value to 20 to allow the single user account to use all the licenses simultaneously Type webots my university edu in the users text area If the account doesn t already exists webot s my university edu will receive an e mail asking to create a user account at Cyberboti
48. the result is that the controller runs as long as the simulation runs 6 1 2 Reading Sensors Now that we have seen how to print a message to the console we shall see how to read the sensors of a robot The next example does continuously update and print the value returned by a DistanceSensor tinclude lt webots robot h gt include lt webots distance_sensor h gt include lt stdio h gt define TIME_STEP 32 int main wb_robot_init ONAN BWN Ke a So Oo WbDeviceTag ds wb_robot_get_device my_distance_sensor wb_distance_sensor_enable ds TIME STEP na N na W while 1 6 1 CONTROLLER PROGRAMMING 157 14 wb_robot_step TIME_STEP 15 double dist wb_distance_sensor_get_value ds 16 printf sensor value is fin dist 17 18 19 return 0 20 As you can notice prior to using a device it is necessary to get the corresponding device tag WboDeviceTag this is done using the wb_robot_get_ device function The WoDe viceTag is an opaque type that is used to identify a device in the controller code Note that the string passed to this function my_distance_sensor in this example refers to a device name specified in the robot description wbt or proto file If the robot has no device with the specified name this function returns 0 Each sensor must be enabled before it can be used If a sensor is not enabled it returns unde
49. the children field of the Solid node and add a Shape node to it Add a Sphere node as the geomet ry field of the just created Shape node Add another Sphere node to the boundingObject field of the Solid Finally add a Physics node to the physics field of the Solid By modifying the translation field of the Solid node place the ball in front of the robot at 0 0 1 0 2 for example Save the simulation The result is depicted in figure 7 4 hands on 204 CHAPTER 7 TUTORIALS wbt Webots PRO 7 4 1 Simulation View o B GOO B O Ib p W W 0 00 00 000 0001 E gt Floor n gt O EPuck v DEF BALL Solid translation 0 0 1 0 2 rotation0100 scale 111 y children v Shape appearance NULL y geometry DEF BALL_GEOMETRY Sphere radius 0 05 name solid model E description contactMaterial default subdivision Integer O O Figure 7 4 Your first rigid body in Webots When the simulation is started the ball hits the floor You can move the ball by adding a force to it CTRL ALT left click drag The contact points between the ball and the floor can be displayed as cyan lines by enabling the View gt Optional Rendering gt Show Contact Points menu item 7 3 5 Geometries To define the ball we used the Sphere node in two different contexts for the graphical repre sentation children and to define the physical bounds boundingOb ject All Geometry
50. the connection with the real robot should stop Typically a command stopping the real robot actuators should be sent just before stopping the connec tion e bool wbr_has failed This function is called very often by libController to check the validity of the connection The value returned by this function should always match with the connection validity 6 7 WEBOTS PLUGIN 189 e void wbhr_stop_actuators This function is called to stop the actuators of the real robot This is called when the user pressed the pause button of the simulator e int wbr_robot_step int period This function is called when the controller enters in the step loop The aim of this function is to send the actuator commands and then to read the vaues of the enabled sensors The timing problem should be solved there The robot should wait at least period milliseconds and returns the delta time if this period is exceeded As said above all the Webots API functionalities that should work with the real robot have to be wrapped into the remote control library To achieve this e The internal state of the libController has to be setup to match with the current state of the robot Typically when the value of a sensor is known the corresponding wor_sensor_set value has to be called e The commands send to the libController have to be wrapped Typically when the command of an actuator is setup the corresponding wor_actua tor_set_value is called and
51. the walls is the Box node Only one Shape has to be defined for all the walls The expected result is shown in figure 7 7 206 my_webots_projects tutorials worlds obstacles wbt Webots PRO 7 4 1 Simulation View amp 88 CO BO Ik p W W o 00 00 000 ooox E gt Floor A gt O EPuck v DEF BALL Solid translation 0 0 1 0 2 rotation0100 WM scale111 v E children v Shape appearance NULL n SECME DEF BALL GEOMETRY Sphere radius 0 05 E subdivision 2 E name solid E model description contactMaterial default boundingObject USE BALL_GEOMETRY gt Y physics Physics locked FALSE translationStep 0 01 geometry Sphere O DEF BALL_GEOMETRY USE count 1 Transform to e Export CHAPTER 7 TUTORIALS Figure 7 5 DEF USE mechanism on the Sphere node called BALL GEOMETRY Physics Solid Geometry boundingObject geometry Figure 7 6 DEF USE mechanism applied on the Shape node of a Solid 7 3 TUTORIAL 2 MODIFICATION OF THE ENVIRONMENT 20 MINUTES 207 bots_projects tutorials worlds obstacles wbt Webots PRO 7 4 1 Simulation View U e Goo SBO b gt gt gt DEF WALL 3 Solid E DEF WALL 4 Solid E translation 0 0 05 0 5 0 00 00 000 0 00x W rotation 0 1 0 1 5708 scale 111 gt children name solid model E description contactMaterial default boundingObject USE WALL_SHAPE physics NULL
52. useful to also add a robot window plugin see subsection 6 6 2 to graphically display specific sensor values motor commands or a stop button Such a remote control system is designed to be implemented in C C as explained in section 6 6 however it can also be implemented other programming languages creating a wrapper 154 CHAPTER 5 DEVELOPMENT ENVIRONMENTS 5 8 2 Cross compilation Overview Developing a cross compilation system will allow you to recompile your Webots controller for the embedded processor of your own real robot Hence the source code you wrote for the Webots simulation will be executed on the real robot itself and there is no need to have a permanent PC connection with the robot as with the remote control system This is only possible if the processor on your robot can be programmed respectively in C C Java or Python It is not possible for a processor that can be programmed only in assembler or another specific language Webots includes the source code of such a cross compilation system for the e puck and the Hemisson robot Samples are located in the WEBOTS_MODULES_PATH projects robots directory Developing a custom library Unlike the remote control system the cross compilation system requires that the source code of your Webots controller be recompiled using the cross compilation tools specific to your own robot You will also need to rewrite the Webots include files to be specific to your own robot In simple c
53. without the WoDeviceTag parame ter 6 4 2 Controller Class The C Java Python controller implementation should be placed in a user defined class derived from one of the Webots class Robot DifferentialWheels or Supervisor It is important that the controller class is derived from the same class as that used in Scene Tree oth erwise some methods may not be available or may not work For example if in the Scene Tree a robot is of type Dif ferentialWheel1s then the corresponding C Java Python controller 178 CHAPTER 6 PROGRAMMING FUNDAMENTALS Robot getLED string LED Pu step int int AAA getName string 0 DifferentialWheels Supervisor Differentialwheels simulationRevert void setSpeed int int void getRoot Node getFromDef Node OtherDevices Ao A getField string Field getSFVec2f double Figure 6 2 A small subset of Webots oriented object APIs class must extend the DifferentialWheels class If in the Scene Tree a robot is of type Supervisor then the C Java Python controller class must be derived from the Supervi sor class etc As you can see in figure 6 2 both DifferentialWheels and Supervisor are subclasses of the Robot class Hence it is possible to call the Robot s methods such as e g step or get LED from the DifferentialWheels and Supervisor controllers But
54. 2 will limit the use of Webots to any machine whose IP address starts with 128 179 67 and also to the machine whose IP address is 128 178 12 122 Machines that do not match the values provided in the IP range field won t be able to access the licenses Making things even simpler for students To save the students from having to type an e mail address and password on the first run of We bots you may want to do it for them before the class starts If you do it from the user account they are supposed to use this information will be saved and the students won t need to enter it again You may also automate this process by copying an already configured Webots preferences to all the user accounts used by the students On Windows the Webots preferences are stored in the registry under the HKEY_CURRENT_USER SOFTWARE Cyberbotics key so you need to use a tool that copies registry keys across user accounts On Mac OS X the Webots prefer ences are stored in a file under the user home directory at Library Preferences com cyberbotics Webots8 3 2 plist On Linux the Webots preferences are stored in a file under the user home directory at config Cyberbotics Webots8 3 2 conf 1 6 3 Homework If no IP restriction is set see above then the students will be able to use Webots anytime from any computer including their own personal computers In such a case it s better to use multiple user accounts rather than a single one to avoid that a f
55. 28 4 5 2 Java and Java Compiler Installation 128 4 5 3 Link with external jar files in 2 xe kw ee he eee REESE eH Es 130 4 5 4 Source Code of the Java AP 2 2228 eee ee ee eee ee 130 do Une PON ne as fd i Gites Bs Sestak ais ae Gs eek ost dy SMe Re SA a h 131 Sl Introduction Ia ede eda eda edn ee heehee Aaa needs 131 4 6 2 Python Installation 222 3 26 e s ha e RARA RA A 131 46 3 Source ode of the Python APL 5 4405 ye 64 hoe R BAR SEDO ERY 132 4T seme MATLAB 22 2282e4 6u ude edu at ed 132 471 Introduchonto MATLAB io eee gw Ok avd a Ged ood 132 Ae How trun the Examples socos sores Soe OE A SERS EASE Ho PRY 132 4 73 MATLAB installation 444 444 45 4484 e Igi S45 84 133 4 7 4 Display information to Webots console 133 47 0 Compatibility Issues 2 4 4 240240 0468 e a e eR ee 134 Oe Use KOS 2664 664494 24 G54 BS EEHASH ASHES a LO 134 ASI Whatis ROSS so nee maemae 4 984 0 6 A 134 4 8 2 KOS for Webots 2 044 e244 aens ee due eee see eee eeu eee 135 4 9 Interfacing Webots to third party software with TCP IP 137 A 2 2 40 44544 2 4 5 44 644688 OHSS O oR ASRS 137 492 WieanOVANISEES ese ek ee Se ea ESSER RS ERR EES 137 a E AA 138 Development Environments 139 Sl Webots Built in Edit r 2 s s i msi AAA 139 5 1 1 Compiling with the Source Code Editor 139 5 2 The standard File Hierarchy of a Project 2446 be ee Ree we ew OO 141 CONTENTS 1
56. 3 5 2 1 The Root Directory oF a Project os 4 bam rs ee Oe Oe pa EN 141 5 2 2 TIME Project Files a oe deo Be oe He ee HER RE REE OS 142 52 3 The controllers Directory 24 4445 444 eR eRe ERE ERE EES 142 5 3 Compiling Controllers in a Terminal 4644 86684 bee eee de es 142 5341 MacOS atid DEE so esc ese oe eR Re REM e E 142 5 32 WINDOWS 622054 2520546422 2e EHP A a a 143 54 Using Webots Makemles lt o oos e scs acs e sotie ook OS Oe ke De ee 143 SA Whatare Makefiles o so seca ui ias sit hak mai 143 5 4 2 Controller with Several Source Files C C 144 5 4 3 Using the Compiler and Linker Flags C C 144 55 Debugging C C Controllers 2 2 iad ee iae chet he vente nwwde 146 3 1 Controller processes ao ke k eh ee A ee Bes 146 5 5 2 Using the GNU debugger with a controller ooo lt 147 5 6 Using Visual C with Webots 1 428225 e054 284 Yee Ee whe 148 56 1 Introduction lt ar he he eh ee ee ee Bas 148 50 2 SOOM A 149 5 7 Starting Webots Remotely ssh o o 151 a Using te sshcommand errar ar ir in 151 5 7 2 Terminating the ssh session ea vee sr a ee ade 152 5 8 Transfer to your own robot 2 44424 454 644 420 49444449444 4 152 5 8 1 Remot control s s ss 42653465648 48 2 oH eee ERA eS 153 5 8 2 Cross compilation 4 ea ys ek oe eae RSS RS ER OO EES 154 5 8 3 Interpreted language su caras ok RAR EAS 154 6 Programming Fundamentals 155
57. 3D simulation the Scene tree which is a hierarchical representation of the current world the Text editor that allows to edit source code and finally the Console that displays both compilation and controller outputs The GUI has nine menus File Edit View Simulation Build Robot Tools Wizards and Help 2 3 1 File Menu The File menu allows you to perform usual file operations loading saving etc The New World menu item and button opens a new world in the simulation window containing only an ElevationGrid displayed as a chessboard of 10 x 10 squares on a surface of 1 m x 1 m a The Open World menu item and button opens a file selection dialog that allows you to choose a wbt file to load 2 3 THE USER INTERFACE 39 home projects contests robotstadium worlds robotstadium_nao_vs_nao wbt Webots PRO 7 3 0 File Edit View on Build Tools Wizards Help gt DEF YELLOW_GOAL Goal gt DEF BLUE_GOAL Goal y O DEF BALL Ball translation 1 46228 0 0323921 0 110715 rotation 0 0444057 0 144707 0 988478 0 Robotstadium 0 Ollers nao_soccer_supervisor nao_soccer_supervisor c O Y 658600 SBO Ib p W W 0 00 42 960 013x EQ De B8BBO0 QA 49 SoccerField j men pa gt walls Team 0 0 0 A Team nao_soccer_supervisor c EJ nao_team_0 cpp FieldPlayer cpp Y 157 return playerID teams swapped MAX_NUM 158 159 160 static int get_red robot index int playerID 161 return play
58. 4 Wheels Robot The aim of this tutorial is to create your first robot from scratch This robot will be made of a body four wheels and two distance sensors The result is depicted in figure 7 13 The figure 7 14 shows the robot from a top view 7 7 1 New simulation Save the world of the previous tutorial as 4_ wheels_robot wbt hands on 0 Remove the nodes defining the e puck the ball the dumbbell and the contact properties The ground the walls and the lighting are kept hands on 7 7 2 Separating the Robot in Solid Nodes Some definitions are required before giving rules to create a robot model The set containing the Solid node and all its derived nodes is called the solid nodes A similar definition is applied for the Device Robot Joint and Motor nodes You can get more information about the node hierarchy in the Reference Manual Note that the solid nodes and device nodes is close but don t match perfectly 224 CHAPTER 7 TUTORIALS Figure 7 13 3D view of the 4 wheels robot Note that the coordinate system representations of the robot body and of its wheels are oriented the same way Their x vector in red defines the left of the robot their y vector in green defines the top of the robot and their z vector in blue defines the front of the robot The distance sensors are oriented in a different way their x vector indicates the direction of the sensor 0 1 0 1 Figure
59. 7 6 1 10 Languages settings The runtime ini file may also contain language specific sections named java python and matlab Each of this section may include two keys namely COMMAND and OPTIONS The COMMAND key allows you to define a specific version of the language interpreter whereas the OPTIONS key allows you to specific options that will be passed immediately to the language interpreter For example 1 runtime ini for a Python controller on Mac OS X 2 3 python 4 COMMAND opt local bin python2 7 5 OPTIONS m package name given In the above example the resulting command issued by Webots will be opt local bin python2 7 m package name given my_controller py possibly followed by the value of the controllerArgs field of the corresponding Robot node 1 vuntime ini for a Java controller on Windows 2 3 environment variables with relative paths 4 CLASSPATH lib MyLibrary jar 5 6 java 7 COMMAND javaw exe 8 OPTIONS Xms6144k The Java classpath or cp option is automatically generated from the CLASSPATH environment variable Therefore you should not add it to the OPTIONS key but rather to a standard environment variable in your runtime ini file In the above example the final classpath op tion passed to the Java virtual machine includes WEBOTS_HOME 1ib Controller jar either the current directory or if present the con troller jar fil
60. API in a C controller you need to add this line in your controller Makefile USE_C_API true 146 CHAPTER 5 DEVELOPMENT ENVIRONMENTS Adding Debug Information If you need to debug your controller you need to recompile it with the debug target from a terminal make debug This will instruct gcc to add debugging information so that the executable can be debugged using gcc 5 5 Debugging C C Controllers 5 5 1 Controller processes In the Webots environment the Webots application and each robot C C controller are executed in distinct operating system processes For example when the soccer wbt world is executed there is a total of eight processes in memory one for Webots six for the six player robots and one for the supervisor To debug a C C controller with Visual C please see here When a controller process performs an illegal instruction it is terminated by the operating system while the Webots process and the other controller processes remain active Although Webots is still active the simulation blocks because it waits for data from the terminated controller So if you come across a situation where your simulation stops unexpectedly but the Webots GUI is still responsive this usually indicates the crash of a controller This can easily be confirmed by listing the active processes at this moment For example on Linux type ps e 12751 pts 1 00 00 16 webots 13294 pts 1 00 00 00 soccer_pla
61. Buchli Alessandro Crespi Ludovic Righetti Julien Gag net Lukas Hohl Pascal Cominoli St phane Mojon J r me Braure Sergei Poskriakov An thony Truchet Alcherio Martinoli Chris Cianci Nikolaus Correll Jim Pugh Yizhen Zhang Anne Elisabeth Tran Qui Gr gory Mermoud Lucien Epinet Jean Christophe Zufferey Laurent Lessieux Aude Billiard Ricardo Tellez Gerald Foliot Allen Johnson Michael Kertesz Simon Garnieri Simon Blanchoud Manuel Jo o Ferreira Rui Picas Jos Afonso Pires Cristina Santos Michal Pytasz and many others Moreover many thanks are due to Cyberbotics s Mentors Prof Jean Daniel Nicoud LAMI EPFL Dr Francesco Mondada EPFL Dr Takashi Gomi Applied AI Inc Finally thanks to Skye Legon and Nathan Yawn who proofread this guide Contents 1 Installing Webots 19 Ll Webals licensGsS n cca eds uw teedacde eds teat hushe ended 19 Lado Webots PRO 2022224052 624 eee ee Pee eee AA 19 Mi Webas BDU oci ooe ue aoe me oe ae oe we Oe Ge ee ee ee wt 19 LLS Webots MOD esca Se Bs te OE BE ER A OR 20 11 4 Webots licences overview es eeu Sew oe SESE E RES EEE SOs 20 1 2 System requirements gt i ee ca c e 640244425 44544848485 20 1 3 Verifying your graphics driver installation 21 Lol Supported graphics Cards 2 14 gen decu A Ge ede i a a D ees 21 1 3 2 Unsupported graphics cards oaoa a 21 1 3 3 Upgrading your graphics driver 224 bee a 22 Lom Hardware ac
62. DifferentialWheels DistanceSensor Braitenberg Koala In this example you can see a Koala robot from K Team moving inside an arena while avoiding the walls Like many other examples this one uses the braitenberg controller The source code for this controller is located in the WEBOTS_MODULES_PATH projects default controllers braitenberg directory 3 5 REAL ROBOTS 117 Figure 3 57 magellan wbt 3 5 25 magellan wbt Keywords DifferentialWheels DistanceSensor Braitenberg Magellan In this example you can see a Magellan robot moving inside an arena while avoiding the walls As this robot is no longer produced its world file is in the others worlds directory Like many other examples this one uses the braitenberg controller The source code for this con troller is located in the WEBOTS_MODULES_PATH projects default controllers braitenberg directory 118 CHAPTER 3 SAMPLE WEBOTS APPLICATIONS Figure 3 58 pioneer2 wbt 3 5 26 pioneer2 wbt Keywords DifferentialWheels DistanceSensor Braitenberg Pioneer 2 In this example you can see a Pioneer 2 robot from ActivMedia Robotics moving inside an arena while avoiding the walls Like many other examples this one uses the braitenberg con troller The source code for this controller is in the WEBOTS_MODULES_PATH projects default controllers braitenberg directory 3 5 REAL ROBOTS 119 Figure 3 59 rover wbt 3 5 27 rover wbt Keywords DifferentialWheels bump
63. General gt Output File ProjectName exe Now we need to tell Visual C to use the Cont roller 1ib import library Linker gt Input gt Additional Dependencies Controller lib Linker gt General gt Additional Library Directories C Program Files Webots lib If you want to use the C API you should skip step 5 and go directly to step 6 If you want to use the C API follow these instructions In Property Pages in the Configuration Properties add the path to Webots hpp files C C gt General gt Additional Include Directories C Program Files Webots include controller c C Program Files Webots include controller cpp Now you should have the path to both the h and the hpp files Then you need to add Webots C wrappers to your project The C wrappers are cpp files that implement the interface between the C API and the C API You can proceed like this In Visual C in the Solution Explorer right mouse click on the Sources Files folder then select Add gt New Filter This should create a NewFilter1 subfolder in your Sources Files folder Then select the NewFilter1 and with the right mouse button choose the Add gt Existing Item menu In the file dialog go to the C ProgramFiles Webots resources languages cpp directory then select all the cpp files but no other file in that directory and hit the Add button This should add the Accelerometer cpp Camera cpp Compass cp
64. Hide All Camera Overlays item is checked then the camera device overlays will not be visible in the 3D view independently from the status of Camera Devices menu items A Camera Devices menu item is disabled if the overlay s texture is shown in an external window by double clicking on it The Display Devices submenu contains the list of all the display devices of the selected robot and lets the user show or hide single display overlay images by checking or unchecking the corresponding item Display overlays differ from the camera overlays because of their cyan border Note that if the Hide All Display Overlays item is checked then the display device overlays will not be visible in the 3D view independently from the status of Display Devices menu items A Display Devices menu item is disabled if the overlay s texture is shown in an external window by double clicking on it On the other hand the following items are always active and apply to all the robot in the world The Hide All Camera Overlays option hides all the camera devices overlays in the 3D view inde pendently from the specific robot s device option set in Camera Devices submenu The Hide All Display Overlays option hides all the display devices overlays in the 3D view inde pendently from the specific robot s device option set in Display Devices submenu 2 3 THE USER INTERFACE 45 2 3 7 Tools Menu The Tools menu allows you to open various Webots windows The 3D View menu it
65. ML keywords 92 3 4 Geometries CHAPTER 3 SAMPLE WEBOTS APPLICATIONS This section shows the geometric primitives available in Webots The world files for these exam ples are located in the sample geometries worlds directory In this directory you will find the following world files box wbt cone wbt convex_polygon wbt cylinder wbt high resolution indexedfaceset wbt non convex polygon wbt physics_primitives wbt polyhedra wbt sphere wbt textured_shapes wbt webots_box wbt 3 5 REAL ROBOTS 93 Figure 3 33 aibo_ers210_rough wbt 3 5 Real Robots This section discusses worlds containing models of real robots The world files for these exam ples are located in the robot s robot_name worlds directory and the corresponding controllers are located in the robot s robot_name controllers directory 3 5 1 aibo_ers210_rough wbt Keywords Aibo Legged robot uneven ground IndexedFaceSet In this example you can see a silver Aibo ERS 210 robot walki texture ng on an uneven floor while a ball rolls and falls off The uneven floor is principally made of a 1 IndexedFaceSet 94 CHAPTER 3 SAMPLE WEBOTS APPLICATIONS Figure 3 34 aibo_ers7 wbt 3 5 2 aibo ers7 wbt Keywords Aibo ERS 7 legged robot soccer field Charger toys beacon bone In this example you can see a silver Aibo ERS 7 robot walking on a textured soccer field On this field you can also see its toys a ball a
66. Mesa 6 5 2 In this case you should definitely install the hardware driver On Ubuntu the driver can usually be installed automatically from the Additional Drivers tab of the Software amp Update window Otherwise you can find out what graphics hardware is installed on your computer by using this command nttp downloadcenter intel com http intellinuxgraphics org 1 3 VERIFYING YOUR GRAPHICS DRIVER INSTALLATION 23 S lspci grep VGA 01 00 0 VGA compatible controller nVidia Corporation GeForce 8500 GT rev al Then you can normally download the appropriate driver from the graphics hardware manufac turer s website http www nvidia com for an nVidia card or http www amd com for a ATI graphics card Please follow the manufacturer s instructions for the installation Windows 1 Right click on My Computer 2 Select Properties 3 Click on the Device Manager tab 4 Click on the plus sign to the left of Display adapters The name of the driver ap pears Make a note of it 5 Go to the web site of your card manufacturer http www nvidia com for an nVidia card or http www amd com for a ATI graphics card 6 Download the driver corresponding to your graphics card 7 Follow the instructions from the manufacturer to install the driver 1 3 4 Hardware acceleration tips Linux Depending on the graphics hardware there may be a huge performance drop of the rendering system up to 10x when
67. ORIALS Figure 7 15 High level representation of the 4 wheels robot 7 7 3 HingeJoints The initial position of the Wheel is defined by the translation and the rotation fields of the Solid node While the rotation origin anchor and the rotation axis axis are defined by the optional HingeJointParameters child of the HingeJoint node For the first wheel the Solid translation should be defined to 0 06 0 0 05 in order to define the relative gap between the body and the wheel The HingeJointParameters anchor should also be defined to 0 06 0 0 05 to define the rotation origin relatively to the body Finally the HingeJointParameters axis should define the rotation axis In our case it s along the x axis so 1 0 0 Add a HingeJointParameters node and enter the field values as described above Some signs have obviously to be updated for other wheels hands on We want now to implement the cylinder shape of the wheels As the Cylinder node is defined along the y axis a Transform node should encapsulate the Shape to rotate the Cylinder along the along the x axis hands on Complete the missing nodes to get the same structure as the one depicted in figure 7 16 Don t forget the Physics nodes Rotate the Transform node by an Euler axis and angle of 0 0 1 Pi 2 in order to inverse the x axis and the y axis The Cylinder should have a radius of 0 04 and a height of 0 02 Set the color of the wheels to green
68. PRS 222 TOY Conclusi n s oe ee dae da a 223 7 7 Tutorial 6 4 Wheels Robot ss ed ce ra ARA A A 223 AAA a A 223 7 72 Separating the Robot in Solid Nodes o 223 Tia Hingeloints 2 23 ane RA hae Ged ee Bede Be 226 TA SONSONS lt A ARRE AA A eee 221 Tel Cobol o sccorisrircas rar rara e 227 LIO AGOMSIUSIOO ya ar AAA AA AAA 228 28 Tulonal 7 Use ROS 2 ead eee ede eae eo Eee eS ee Ow Be 229 7 8 1 Creating a Webots project that contains a ROS package 229 Te2 COncl Sion edo RNA AAA 233 79 Going Further s e ses ene en o eae A ae RS AR ESS 233 8 Robots 235 8 1 Usingthee p ckrobot 12 426 44642448458 eet detar iienaa 235 5 1 1 Overview oftherobot 2 424424 6284858248 REM EER eS 235 61 2 Simulation model o ses ea Beck ec he bee bee bee oe wee 236 Gb o AAA 240 CONTENTS 17 5 2 Using the Nad TODO s sb e s dosor koso ee Be ee aoe ee ee eS 245 Bel Tntrodu ctiom ssa s ss ess wae AAA e E a eS 245 8 2 2 Using Webots with Choregraphe ooa eee be ees 245 Dee Naomodels lt ic eaae a a 6454 445 2534544584884 5 246 5 24 Using motion DORES gt lt soed ee ee hw See Bo Be Boe ee a Ea 246 De USM Cameras 5 34 o oR AO De MDH OSES DA 247 8 2 6 Using Several Nao robots orcas A he eee ees 247 8 2 7 Getting the right speed for realistic simulation 248 0 2 9 Known Problems lt vo eS eae ee He Gos ee ae B ae Be ae aO Oe 248 8 3 Using the Thymio II robot sce ae ee te ee oe deer ee ted ee
69. Pause the simulation push the Pause button in Webots 3D View Revert the simulation push the Revert button in Webots 3D View In Webots Scene Tree select a top level nodes e g the Nao robot 2 3 4 Then push the Add button a dialog appears 5 In the dialog select PROTO Webots gt robots 6 Then select one of the Nao models from the list the Nao is added to the current world 7 Select the Nao in the 3D view and move it away from the other one SHIFT left mouse button 8 Select the controllerArgs field in the newly created robot and increase the port num ber e g 9560 9 Save the wbt file push the Save button 10 Now you can push the Real time button to run the simulation with several robots Repeat the above procedure for each additional robot that you need Remember that every robot must have a different port number specified in controllerArgs 248 CHAPTER 8 ROBOTS 8 2 7 Getting the right speed for realistic simulation Choregraphe uses exclusively real time and so the robot s motions are meant to be carried out in real time The Webots simulator uses a virtual time base that can be faster or slower than real time depending on the CPU and GPU power of the host computer If the CPU and GPU are powerful enough Webots can keep up with real time in this case the speed indicator in Webots shows approximately 1 0x otherwise the speed indicator goes below 1 0x Choregraphe motions will play accurately only if Webots
70. Process Com munication IPC An example of remote control is implemented for the e puck robot in the file 138 CHAPTER 4 LANGUAGE SETUP WEBOTS_MODULES_PATH projects robots e puck worlds e puck wbt direc tory of Webots The third advantage is that you can spread your controller programs over a network of com puters This is especially useful if the controller programs perform computationally expensive algorithms such as genetic algorithms or other learning techniques Finally you should set the controlled robot to synchronous or asynchronous mode depending on whether or not you want the Webots simulator to wait for commands from your controllers In synchronous mode with the synchronization field of the robot equal to TRUE the simulator will wait for commands from your controllers The controller step defined by the robot_step parameter of the tcpip controller will be respected In asynchronous mode with the synchronization field of the robot set to FALSE the simulator will run as fast as possible without waiting for commands from your controllers In the latter case you may want to run the simulation in real time mode so that robots will behave like real robots controlled through an asynchronous connection 4 9 3 Limitations The main drawback of TCP IP interfacing is that if your robot has a camera device the protocol must send the images to the controller via TCP IP which might be network intensive Hence it is recommended to
71. TEP readSensors actuateMotors nb WN Re Here is a complete example of using sensors and actuators together The robot used h ere is Dis a DifferentialWheels using differential steering It uses two proximity sensors tanceSensor to detect obstacles 162 CHAPTER 6 PROGRAMMING FUNDAMENTALS finclude lt webots robot h gt include lt webots differential_wheels h gt include lt webots distance_sensor h gt define TIME _STEP 32 int main wb_robot_init WoDeviceTag left_sensor wb_robot_get_device left_sensor WoDeviceTag right_sensor wb_robot_get_device right_sensor y 12 wb_distance_sensor_enable left_sensor TIME_STEP Re PSP OowomananktWN a 13 wb_distance_sensor_enable right_sensor TIME_STEP 14 15 while 1 16 wb_robot_step TIME_STEP 17 18 read sensors 19 double left_dist wb_distance_sensor_get_value left_sensor i 20 double right_dist wb_distance_sensor_get_value right_sensor 21 22 compute behavior 23 double left compute_left_speed left_dist right_dist 24 double right compute_right_speed left_dist right_dist 25 26 actuate wheel motors 21 wb_differential_wheels_set_speed left right 28 29 30 return 0 31 6 1 6 Using Controller Arguments In the wht file it is possible to specify arguments that are passed to a cont
72. TS_MODULES _PATH projects robots e puck plugins robot_windows e puck_window 6 6 3 Qt utility library In order to facilitate the creation of robot window plugins using the Qt framework Webots has a utility library allowing to hide the complexity of the management of the robot windows This library contains various classes including a subclass of QMainApplication managing the pipe events a subclass of QMainWindow dealing with the close events a class to handle Webots standard paths and a collection of widgets to display the Webots devices The source code of the generic robot window is a good example illustrating how to use this library The location of the qt utility library is WEBOTS_HOME resources projects libraries qt_ utils 6 6 CONTROLLER PLUGIN 187 Robot View NAO_H25_V40 GPS Accelerometer Gyro InertialUnit DistanceSensor Motor Camera TouchSensor Motion Editor Motion file options Play options Pose insertion options D gt BOB 4 gt Loop C Pin Y Fixed step 40ms Motion HandWave 00 00 360 Posel0 Pose Pose14 00 00 400 Posell 1 5 RShoulderPitch 00 00 440 Posel2 0 39 RShoulderRoll 00 00 480 Posel3 LShoulderPitch 00 00 520 Posel4 00 00 560 Posel5 00 00 600 Posel6 00 00 640 Posel7 00 00 680 Posel8 00 00 720 Posel9 State RShoulderPitch 00 00 760 Pose20 00 00 800 Pose21 Enabled 1 496 00 00 840 Pose22 00 00 880 Pose23 00 00 920 Pose24 2 09 be AAA tet Figure 6 4 Motion edit
73. This is an example of the flying blimp robot developed at the Laboratory of Intelligent Systems LIS at EPFL You can use your keyboard or a joystick to control the blimp s motion across the room Use the up down right left page up page down and space reset keys Various Transform and IndexedFaceSet nodes are used to model the room using textures and transparency A physics plugin is used to add thrust and other forces to the simulation 3 1 SAMPLES 61 Figure 3 2 gantry wbt 3 1 2 gantry wbt Keywords Gantry robot gripper Hanoi towers linear motors recursive algorithm In this example a gantry robot plays Towers of Hanoi by stacking three colored boxes The gantry robot is modeled using a combination of LinearMotor and RotationalMotor de vices A recursive algorithm is used to solve the Hanoi Towers problem 62 CHAPTER 3 SAMPLE WEBOTS APPLICATIONS Figure 3 3 hexapod wbt 3 1 3 hexapod wbt Keywords Legged robot alternating tripod gait linear motor In this example an insect shaped robot is made of a combination of LinearMotor and Ro tationalMotor devices The robot moves using an alternating tripod gait 3 1 SAMPLES Figure 3 4 humanoid wbt 3 1 4 humanoid wbt Keywords Humanoid QRIO robot In this example a humanoid robot performs endless gymnastic movements 63 64 CHAPTER 3 SAMPLE WEBOTS APPLICATIONS Figure 3 5 moon wbt 3 1 5 moon wbt Keywords DifferentialWheels
74. UNIX pipe client program Khepera In this example you can see a Khepera robot from K Team inside an arena The controller for this robot opens a UNIX pipe in order to receive commands using the Khepera serial communi cation protocol This example is provided with a sample client program which interacts with the controller of the robot to make it move straight forward until it detects an obstacle This client program client must be launched separately from Webots The source code for this controller and for the client program are in the pipe directory E As this example is based on standard UNIX pipes it does not work under Windows 3 5 REAL ROBOTS 115 Figure 3 55 khepera_tcpip wbt 3 5 23 khepera tcpip wbt Keywords DifferentialWheels TCP IP client program Khepera In this example you can see a Khepera robot from K Team inside an arena The controller for this robot acts as a TCP IP server waiting for a connection Through this connection the robot can receive commands using the Khepera serial communication protocol This example is provided with a sample client program which displays a command prompt with which you can control the movements of the robot This client program client must be launched separately from Webots The source code for this controller and for the client program are in the tcpip directory 116 CHAPTER 3 SAMPLE WEBOTS APPLICATIONS Figure 3 56 koala wbt 3 5 24 koala wbt Keywords
75. Webots User Guide release 8 3 2 Copyright 2015 Cyberbotics Ltd All Rights Reserved www cyberbotics com December 16 2015 Permission to use copy and distribute this documentation for any purpose and without fee is hereby granted in perpetuity provided that no modifications are performed on this documenta tion The copyright holder makes no warranty or condition either expressed or implied including but not limited to any implied warranties of merchantability and fitness for a particular purpose regarding this manual and the associated software This manual is provided on an as is basis Neither the copyright holder nor any applicable licensor will be liable for any incidental or con sequential damages The Webots software was initially developed at the Laboratoire de Micro Informatique LAMI of the Swiss Federal Institute of Technology Lausanne Switzerland EPFL The EPFL makes no warranties of any kind on this software In no event shall the EPFL be liable for incidental or consequential damages of any kind in connection with the use and exploitation of this software Trademark information Aibo is a registered trademark of SONY Corp Radeon is a registered trademark of ATI Technologies Inc GeForce is a registered trademark of nVidia Corp Java is a registered trademark of Sun MicroSystems Inc Khepera and Koala are registered trademarks of K Team S A Linux is a registered trademark of Linus Torvalds
76. _node wb_supervisor_node_get_from_def MY_ROBOT 10 WbFieldRef trans_field wb_supervisor_node_get_field robot_node translation 11 12 while 1 13 this is done repeatedly 14 const double trans wb_supervisor_field _get_sf_vec3f trans_field 15 printf MY_ROBOT_ is at position g _ gq gin trans 0 trans 1 trans 2 16 wb_robot_step 32 17 18 19 return 0 20 Note that a Supervisor controller must include the supervisor h header file in addition to the robot h header file Otherwise the Supervisor works like a regular Robot controller and everything that was explained in the Controller Programming section does also apply to Supervisor Programming As illustrated by the example it is better to get the WoNodeRefs and WoFieldRefs only once at the beginning of the simulation keeping the invariants out of the loop The call to wb supervisor node get_from def searches for an object named MY ROBOT in the Scene Tree Note that the name in question is the DEF name of the object not the name field which is used to identify devices The function returns a WoNodeRef which is an opaque and unique reference to the corresponding Scene Tree node Then the call to wo_supervi sor_node_get_field finds aWbFieldRef in the specified node The translation field represents the robot s position in the global world coordinate system In the while loop the call to wo_supervisor_field_g
77. _team_1 nao_soccer_supervisor KICK OFF nao_soccer supervisor RED TOUCH nao_soccer_supervisor RED TOUCH WNHO Heme CameraTop pixel 154 19 ADD8E6 Figure 2 1 Webots GUI The Open Recent World menu item gives the possibility of reopening a wbt file that was opened recently by choosing it from the list displayed in the submenu The Open Sample World menu item opens a dialog listing all the available sample worlds where it is possible to search for a specific wbt file to load by entering the file name or part of it in the search field B The Save World menu item and button saves the current world using the current filename the filename that appears at the top of the main window On each Save the content of the wbt file is overwritten and no backup copies are created by Webots therefore you should use this button carefully and eventually do safety copies manually The Save World As menu item and button saves the current world with a new filename entered by the user Note that a wbt file should always be saved in a Webots project directory and in the worlds subdirectory otherwise it will not be possible to reopen the file 2 The Revert World menu item and button reloads the current world from the saved version and restarts the simulation from the beginning 40 CHAPTER 2 GETTING STARTED WITH WEBOTS When opening or reverting a world if the world takes more than 2 seconds to load a window will pop up
78. a_tcpip wbt and can be found in the WEBOTS_MODULES_PATH projects robots khepera kheperal worlds di rectory of Webots The simulated Khepera robot is controlled by the tcpip controller which is in the controllers directory of the same project This small C controller comes with full source code in tcpip c so that you can modify it to suit your needs A client example is provided in client c This client may be used as a model to write a similar client using the programming language of your third party software This has already been implemented in Lisp Mand MATLAB by some Webots users 4 9 2 Main advantages There are several advantages of using such an interface First you can have several simulated robots in the same world using several instances of the same tcpigp controller each using a different TCP IP port thus allowing your third party software to control several robots through several TCP IP connections To allow the t cpip process to open a different port depending on the controlled robot you should give a different name to each robot and use the robot_get _ name in the tcpip controller to retrieve this name and decide which port to open for each robot The second advantage is that you can also control a real robot from your third party software by simply implementing your library based on the given remote control library Switching to the re mote control mode will redirect the input output to the real robot through the Inter
79. ace this light node by a DirectionalLight node casting shadows Remove the PointLight node and add a new DirectionalLight node instead Set its ambientIntensity field to 0 5 its cast Shadows field to TRUE hands on and its direction field to 1 2 1 7 4 TUTORIAL 3 APPEARANCE 15 MINUTES 209 7 4 3 Modify the Appearance of the Walls The aim of this subsection is to color the walls with blue The Appearance node of the Shape node determines the graphical appear ance of the object Among other things this node is responsible for the color theory and texture of objects In the Shape node representing graphically the first wall add an Appearance node to the appearance field Then add a Material node to the material field of the freshly created Appearance node Set its diffuseColor field hands on to blue using the color selector If the DEF USE mechanism of the previous tutorial has been correctly implemented all the walls should turn blue 7 4 4 Adda Texture to the Ball The aim of this subsection is to apply a texture on the ball A texture on a rolling object can help to appreciate its movement Similarly add an Appearance node to the ball Instead of a Material node add an ImageTexture node to the texture field of the Appearance node Add an item to the url field using the Add button Then set the value of the newly added url item to WEBOTS_MODULES_PATH projects default worlds textures brick
80. ackward speed 1 2 m s Rotation speed 300 deg s Table 8 7 Pioneer 3 AT features More information on the specifications and optional devices is available on Adept Mobile Robots official webpage Simulation model The Pioneer 3 DX model in Webots is depicted in figure 8 19 This model includes support for two motors the caster wheel 7 LEDs on the control panel and 16 sonar sensors 8 forward facing 8 rear facing for proximity measurements The standard model of the Pioneer 3 DX is provided in the pioneer3dx wbt file which is located in the WEBOTS_MODULES_PATH projects robots pioneer pioneer3dx worlds directory of the Webots distribu tion The pioneer3dx whbt world file shows a simulation example of the Braitenberg avoidance al gorithm based on the use of the 16 sonar sensors see the braitenberg c controller file in the WEBOTS_MOI DULES_PATH projects robots pioneer pioneer3dx controller Bhttp w ww mobilerobots com ResearchRobots PioneerP3DX aspx 258 CHAPTER 8 ROBOTS Figure 8 19 The Pioneer 3 DX model in Webots rightWheel casterWheel ae leftWheel casterWheelRim Figure 8 20 Pioneer 3 DX motor names 8 4 USING THE PIONEER 3 AT AND PIONEER 3 DX ROBOTS 239 directory The pioneer3dx_with_kinect wbt world file in the same directory is a sim ple simulation example of an obstacle avoidance behaviour based on a Microsoft kinect sensor see the obstacle_avoidance_kinect c controller f
81. ad your license agreement carefully before using Webots This license is provided within the software package By using the software and documentation you agree to abide by all the provisions of this license 1 5 3 License setup A Webots license is originally associated with an e mail address which corresponds to a user account on Cyberbotics s web site When Webots is started for the first time a login dialog invites you to register a user account on Cyberbotics s web site if not already done and to enter the corresponding license information to log in your Webots session The Synchronization field of the Webots login dialog defines how frequently Webots checks the license server Setting this field to a small value will cause more networking activity but will allow you to release the license quickly after a crash This will allow you in turn to restart Webots quicker on another note machine For example if you select 5 minutes you may have to wait for up to 5 minutes if you crashed Webots on a machine and want to restart it on another 1 5 4 License administration If you are the administrator of the license you can log into your Webots account on Cyberbotics web site and go to the Administration page under the My Account tab From there you will be able to monitor your licenses to purchase more licenses to create groups of users and to grant customized user access to your licenses 1 5 5 Module download folder
82. ake replicable deterministic simulations In order for a Webots simulation to be replicable the following conditions must be fulfilled 1 Each simulation must be restarted either by pushing the Revert button or by using the wb_ supervisor_simulation_revert function or by restarting Webots Any other method for resetting the simulation will not reset the physics velocity inertia etc and other simulation data hence the simulation state will be reset only partly The random seeds used by Webots internally are reset for each simulation restarted with one of the above methods 2 The synchronization flag of every robot and supervisor must be TRUE Otherwise the number of physics steps per control step may vary with the current CPU load and hence the robot s behavior may also vary 3 The controllers and physics plugin code must also be deterministic In particular that code must not use a pseudo random generator initialized with an non deterministic seed such as the system time For example this is not suitable for replicable experiments srand time NULL Note that uninitialized variables may also be a source of un deterministc behavior 4 Each simulation must be executed with the same version of the Webots software and on the same OS platform Different OS platforms and different Webots versions may result small numerical differences If the four above conditions are met Webots simulations become replicable This means t
83. al bugs subsist changing the RTT prefered mode from the Webots OpenGL Preferences from Framebuffer Object to Pixelbuffer Object or Direct Copy may fix the problems However this may also impact the 3D performance 1 3 3 Upgrading your graphics driver On Linux and Windows you should make sure that the latest graphics driver is installed On the Mac the latest graphics driver are automatically installed by the Software Update so Mac users are not concerned by this section Note that Webots can run up to 10x slower without appropriate driver Updating your driver may also solve various problems i e odd graphics rendering or Webots crashes Linux On Linux use this command to check if a hardware accelerated driver is installed glxinfo grep OpenGL If the output contains the string NVIDIA ATT or Intel this indicates that a hardware driver is currently installed glxinfo grep OpenGL OpenGL vendor string NVIDIA Corporation OpenGL renderer string GeForce 8500 GT PCI SSE2 OpenGL version string 3 0 0 NVIDIA 180 44 If you read Mesa Software Rasterizer or GDI Generic this indicates that the hardware driver is currently not installed and that your computer is currently using a slow software emula tion of OpenGL glxinfo grep OpenGL OpenGL vendor string Mesa project www mesa3d org OpenGL renderer string Mesa GLX Indirect OpenGL version string 1 4 1 5
84. all Its pur pose is to inform that from this moment the pipe answering from Webots to the controller can receive data If data is coming from the Webots pipe wow_update_gui should return as soon as possible e void whw_update_gui The aim of this function is to process the GUI events until something is available on the Webots pipe e void whw_read_sensors This function is called when it s time to read the sensors values from the Webots API For example in this function the wo_distance_sensor_get_value function can be called e void whw_write_actuators This function is called when it s time to write the actuator commands from the Webots API For example in this function the wo motor_set position function can be called e void wbw_show This function is called when the GUI should be show This can occur either when the user double click on the virtual robot either when he selects the Robot Show Robot Window menu item or either at controller startup if the showRobotWindow field of the Robot node 1s enabled e void x wbw_robot_window_custom_function void x This function can optionally be defined to communicate and pass data from and to the controller program It is called directly by the user from the controller when executing the wb_robot_window_custom_function C function or Robot robotWindowCustomFunction C function You can find more information in the reference manual The internal behavior of th
85. allows to display or to hide the rays in which the pen devices paint These rays are drawn as violet lines if painting is enabled otherwise as gray lines The Show Center Of Mass and Support Polygon allows to display or to hide both the global center of mass of a selected solid with non NULL Physics node and its support polygon By support polygon we mean the projection of the convex hull of the solid s contact points on the horizontal plane which contains the lowest one In addition the projection of the center of mass in the latter plane is rendered in green if it lies inside the support polygon static equilibrium red otherwise This rendering option can be activated only for solids with no other solid at their top If the Disable selection option is enabled it prevents you from changing the selected solid node when clicking on the 3D window This is particularly useful during the modeling phase when you want to change the viewpoint without modifying the visible and selected fields in the scene tree 2 3 4 Simulation Menu The Simulation menu is used to control the execution of the simulation W The Pause menu item and button pauses the simulation la The Step menu item and button executes one basic time step of simulation The duration of this step is defined in the basicTimeStep field of the WorldInfo node and can be adjusted in the scene tree window to suit your needs gt The Real time menu item and button runs t
86. amp a ae oh ee OS Se eS OME BERRA a 181 651 Using ihe MATLAB desktop cook ee E kee eee en 182 COMICS PNG sopla bom ee Moe ae oe he ae oe ee ee eg Bat ee 183 606 1 Fundamentals o rs raspar a war waa aia EE RSS 183 6 6 2 Robot Window Plugin aoaaa aa e 184 a AE 186 OSA Moton Edit r 454454 25 434 A A SHAS e 187 6 6 5 Remote control Plugin 42 2 da ar Gee Boe Bw ee ee eS 188 e AA 189 OAL Physics Plugim oe dos ra be a e A a dood w oe S 190 CONTENTS 15 7 Tutorials 191 TA PEOTOQUIS ES oi 2 odo SESS oe RSS BS AAA Be AA OS 192 FAA IA Wee ona sos he s soe Oe Ow Ow Oe Ce Ae RAROS 192 7 1 2 Create a directory for all your Webots files ee seres 192 BLES Stat NUS semi a ene Oe ee IO 192 LA Create anew Project ae sossa eo AA A AOS 193 7 1 5 The Webots Graphical User Interface GUI zos mar os 193 7 2 Tutorial 1 Your first Simulation in Webots 20 minutes 193 Tal Creteanew World ers es ees AA ees 195 dave Addanepuck Robot isis iio anios 197 7 23 Create anew Controller e ees ees tres ir bee ir See Be es 199 toe Conclusion 22 cnc ede bbe ehe ede ee rre 201 7 3 Tutorial 2 Modification of the Environment 20 minutes 201 73 1 Anew Simulation 4 4 2458 29 aeaaea Ro RSE EES 201 7 3 2 Modification of the Floor 2 222 222 485e eee ev Re eR eR 201 T3 TRES SONG NGOS 0 woh we acie aoe a Se we WO eS A 202 1338 Crewe Ball or iria Se Ge OLED BS Ree RE SS 203 TaS ABONOS aosa sce OR e
87. and out Dragging the mouse horizontally will rotate the camera about the viewing axis Alter natively the mouse wheel alone can also be used for zooming If you are a Mac user with a single button mouse hold the Alt key and press the mouse button to translate the camera according to the mouse motion Hold the control key Ctrl down and press the mouse button to zoom rotate note the camera with the mouse motion 2 4 3 Moving a solid object Currently Webots provides two different ways to move solid objects axis aligned handles and keyboard shortcuts Axis aligned handles When a solid object is selected some arrow shaped handles appear in the 3D window see figure 2 3 These handles can be used to translate and rotate the object along the corresponding axis For moving the object you can simply click on the handle and drag it to the desired position A label will show the currect relative translation or rotation during the movement as shown in figure 2 4 If the Control key Ctrl the handles for resizing the solid object will be displayed instead of translation and rotation handles These resize handles can also be enabled from the Field Editor 2 4 THE 3D WINDOW 49 Figure 2 4 Labels displaying relative translation and rotation when moving objects with handles Translation using keyboard shurtcuts e Translation To move an object parallel to the ground hold down the shift key press the left mouse but
88. and show the progression Using this window it is possible to cancel the loading of the world in that case the empty world will be opened instead note D The New Text File menu item and button opens an empty text file in the text editor w The Open Text File menu item and button opens a file selection dialog that allows you to choose a text file for example a java file to load B The Save Text File menu item and button saves the current text file B The Save Text File As menu item and button saves the current text file with a new filename entered by the user The Save All Text Files menu item saves all the opened and unsaved text files 9 The Revert Text File menu item and button reloads the text file from the saved version The Print Preview menu item opens a window allowing you to manage the page layout in order to print files from the text editor The Print menu item opens a window allowing you to print the current file of the text editor The Import VRML 2 0 menu item adds VRML97 objects at the end of the scene tree These objects come from a VRML97 file you must specify This feature is useful for importing complex shapes that were modeled in a 3D modelling program then exported to VRML97 or VRML 2 0 Most 3D modelling software like 3D Studio Max Maya AutoCAD Pro Engineer AC3D or Art Of Ilusion include the VRML97 or VRML 2 0 export feature Be aware that Webots cannot impor
89. aphical properties of a Solid can be made of several Shape nodes Moreover each Shape node can be placed in a Transform node in order to change its relative position and orientation Group nodes can also be used to group several subnodes We want to implement a dumbbell made of a handle Cylinder and of two weights Sphere located at each end of the handle The figure 7 12 depicts the Solid nodes and its subnodes required to implement the dumbbell Create the dumbbell by following the figure 7 12 Create the handle first without placing it in a Transform node so the handle axis will have the same direction as the y axis of the solid The handle should have a length of 0 1 m and a radius of 0 01 m The weights should have a radius of 0 03 m and a subdivision of 2 The weights can be moved at the handle extremities thanks to the translation field of their Transform nodes hands on 220 CHAPTER 7 TUTORIALS children Transform children children Transform children Cylinder children children Figure 7 12 Representation of the subnodes of a compound solid made of several transformed geometries 7 6 3 Physics Attributes The aim of this subsection is to learn how to set some simple physics properties for a Solid node The Physics node contains fields related to the physics of the current rigid body Solid The mass of a Solid node is given by its density or mass field Only one of these two field
90. ards Menu The Wizards menu makes it easier to create new projects and new controllers The New Project Directory menu item first prompts you to choose a filesystem location and then it creates a project directory A project directory contains several subdirectories that are used to store the files related to a particular Webots project i e world files controller files data files plugins etc Webots remembers the current project directory and automatically opens and saves any type of file from the corresponding subdirectory of the current project directory The New Robot Controller menu item allows you to create a new controller program You will first be prompted to choose between a C C Java Python or MATLAB controller Then Webots will ask you to enter the name of your controller and finally it will create all the necessary files including a template source code file in your current project directory The New Physics Plugin menu item will let you create a new physics plugin for your project Webots asks you to choose a programming language C or C and a name for the new physics plugin Then it creates a directory a template source code file and a Makefile in your current project 46 CHAPTER 2 GETTING STARTED WITH WEBOTS 2 3 9 Help menu In the Help menu the About item opens the About window that displays the license information The Webots Guided Tour menu item starts a guided tour that demonstrates W
91. as several cpp source files then this can be specified like this CXX_SOURCES my_controller cpp my_second_file cpp my_third_file cc Important the build rules require that one of the source files in the list must correspond to the controller name i e controller directory name e g if the controller directory is my_ controller then the list must contain either my_controller c my_controller cpp or my_controller cc accordingly 5 4 3 Using the Compiler and Linker Flags C C These two variables can be used to pass flags to the gcc compiler or linker 5 4 USING WEBOTS MAKEFILES 145 Variable Usage CFLAGS Specifies a list of flags that will be passed to the gcc g compiler INCLUDE Specifies a list of flags that will be passed to the gcc g compiler LIBRARIES Specifies a list of flags that will be passed to the linker Table 5 2 Webots Makefile Variables Adding an External Library C C Webots C C controllers are regular binary executable files that can easily be compiled and linked with external libraries To add an external library it is only necessary to specify the path to the header files and the path and name of the library in the controller s Makefile For example the Idir flag can be used to add a directory to search for include files The LIBRARIES variable can be used to pass flags to the linker For example the Ldir flag can be used to add a directory to search for static or dyna
92. ases you can just rewrite the Webots include files you need as in the hemisson example In more complex cases you will also need to write some C source files to be used as a replacement for the Webots Cont roller library but running on the real robot You should then recompile your Webots controller with your robot cross compilation system and link it with your robot library The resulting file should be uploaded onto the real robot for local execution Examples Webots support cross compilation for several existing commercial robots For the e puck robot this system is fully integrated in Webots and needs no modification in the code For the Hemisson robot this system needs a few include files to replace the Webots API include files For the Khepera robot a specific C library is used in addition to specific include files 5 8 3 Interpreted language In some cases it may be better to implement an interpreted language system This is useful if your real robot already uses an interpreted language like Basic or a graph based control lan guage In this case the transfer is very easy since you can directly transfer the code of your program that will be interpreted to the real robot The most difficult part may be to develop a language interpreter in C or Java to be used by your Webots controller for controlling the simu lated robot Such an interpreted language system was developed for the Hemisson robot with the BotStudio system
93. ast not a Mot or derived node Alternatively it is also possible to make a Motor become passive during the simulation this can be done like this wb_motor_set_motor_force motor 0 0 The effect is similar to turning off the power of a real motor 9 3 5 Isit possible fix immobilize one part of a robot To immobilize one part of the robot you need to fix the part to the static environment This must be done with a physics plugin Webots PRO required You can add a physics plugin with the menu item Wizards gt New Physics Plugin In the plugin code you must simply add an ODE fixed joint between the dBodyID of the robot part and the static environment This can be implemented like this include lt ode ode h gt include lt plugins physics h gt void webots_physics_init get body of the robot part dBodyID body dWebotsGetBodyFromDEF MY_ROBOT_PART get the matching world 212 CHAPTER 9 WEBOTS FAQ dWorldID world dBodyGetWorld body the joint group ID is 0 to allocate the joint normally dJointID joint dJointCreateFixed world 0 attach robot part to the static environment 0 dJointAttach joint body 0 fix now remember current position and rotation dJointSetFixed joint void webots_physics_step nothing to do void webots_physics_cleanup nothing to do You will find the description of Webots physics plugin API in your Reference Manual or on this
94. at the call to wo_robot_step is placed in the innermost loop This allows the motor positions to be updated at each iteration of the loop If wo_robot_step was placed anywhere else this would not work 6 3 Using Numerical Optimization Methods 6 3 1 Choosing the correct Supervisor approach There are several approaches to using optimization algorithms in Webots Most approaches need a Supervisor and hence Webots PRO is usually required A numerical optimization can usually be decomposed in two separate tasks 1 Running the optimization algorithm Systematical Search Random Search Genetic Algo rithms GA Particle Swarm Optimization PSO Simulated Annealing etc 2 Running the robot behavior with a set of parameters specified by the optimization algo rithm One of the important things that needs to be decided is whether the implementation of these two distinct tasks should go into the same controller or in two separate controllers Let s discuss both approaches Using a single controller If your simulation needs to evaluate only one robot at a time e g you are optimizing the lo comotion gait of a humanoid or the behavior of a single robot then it is possible to have both tasks implemented in the same controller this results in a somewhat simpler code Here is a pseudo code example for the systematical optimization of two parameters a and b using only one controller include lt webots robot h gt include lt web
95. ated to the nodes what is their meaning how to create them how they have to be affiliated etc Moreover we will see how to set up physics Several kinds of nodes will be introduced We won t define each of them precisely Their detailed definition can be found in chapter 3 of the Reference Manual Having the nodes chart diagram chapter 2 of the Reference Manual in front of you will also help understanding the nodes inheritance relationship 7 3 1 A new Simulation First we create a new simulation based on the one created in Tutorial 1 Make sure the my_first_simulation wbt world file is open and that the simulation is paused and is at a virtual time of 0 Using the File gt Save hands on World As menu save the simulation as obstacles wbt 7 3 2 Modification of the Floor The default RectangleArena PROTO defines a simple floor pinned on the statical environ ment i e without Physics node and surrounded by walls In order to define an object as static its physics node has not to be set NULL note 202 CHAPTER 7 TUTORIALS Other pre built floors are available in the Webots objects library We will now delete the default arena and add a simple floor that we will manually surround the walls later in this this tutorial To remove the RectangleArena select it in the scene tree view and press the Delete button located in the toolbar hands on In order to add a different floor PROTO se
96. available on Adept Mobile Robots official webpage Simulation model The Pioneer 3 AT model in Webots is depicted in figure 8 15 This model includes support for 4 motors and 16 sonar sensors 8 forward facing 8 rear facing for proximity measurements The standard model of the Pioneer 3 AT is provided in the pioneer3AT wbt file which is lo cated in the WEBOTS_MODULES_PATH projects robots pioneer pioneer3at worlds directory of the Webots distribution The pioneer3at wbt world file is a simulation example of a simple obstacle avoidance be havior based on the use of a SICK LIDAR see the obstacle_avoidance_with_lidar c controller file in the WEBOTS_MODULES_PATH projects robots pioneer pioneer3at controller directory http www mobilerobots com ResearchRobots ResearchRobots P3AT aspx 8 4 USING THE PIONEER 3 AT AND PIONEER 3 DX ROBOTS 255 Figure 8 15 The Pioneer 3 AT model in Webots frontLeftWheel frontRightWheel backLeftWheel backRightWheel Figure 8 16 Pioneer 3 AT motor names 256 CHAPTER 8 ROBOTS so9 sol0 soll sol3 sol4 5 e sol so5 Figure 8 17 Sonar sensors positions The Pioneer 3 AT motors are RotationalMotor nodes named according to figure 8 16 The wb_ set_motor_position and wb_set_motor_velocity functions allow the user to manage the rotation of the wheels The sonar sensors are numbered according to figure 8 17 The angle between two consecutive sensor directions
97. ay last only for the current session or create conflict with other applications or projects Webots offers an elegant solution to this A configuration file named runt ime ini can be added to the controller directory Any envi ronment variable defined in this file will be loaded to the environment each time the controller Starts This configuration file uses the standard INI template that is really simple and easy to write and read It contains pairs of key and value that can be inside sections Comments can be written on a line after using a semicolon character Environment variables in this file can contain references to other environment variables using this syntax MY_VARIABLE_NAME They will be automatically replaced by the actual value already existing in the environment The Webots runt ime ini supports 7 sections e environment variables with relative paths This section should contain only environment variables with relative paths Paths must be separated by the colon symbol and the separator between directories is the slash symbol P Variables declared in this section will be add on every platform On Windows colons will be replaced by semicolon and slash will be replaced by backslash according to the Windows syntax e environment variables 166 CHAPTER 6 PROGRAMMING FUNDAMENTALS Environment variables defined in this section will also be added to the environment on every platform but t
98. be created for each theory rigid body 7 3 TUTORIAL 2 MODIFICATION OF THE ENVIRONMENT 20 MINUTES 203 boundingObject Geometry children geometry Figure 7 3 The simplest model of a rigid body in Webots having a graphical representation Shape a physical bound boundingObject and being in the dynamical environment Physics To define a rigid body you will have to create a Solid node Inside this node you will find differ ent subnodes corresponding to the characteristics of the rigid body The figure 7 3 depicts a rigid body and its subnodes The graphical representation of the Solid is defined by the Shape nodes populating its children list The collision bounds are defined by its boundingObject field The graphical representation and the collision shape are often but not necessarily identical Finally the physics field defines if the object belongs to the dynamical or to the statical envi ronment All these subnodes are optional but the physics field needs the boundingObject to be defined The Geometry box in figure 7 3 stands for any kind of geometrical primitive In fact it can be substituted by a Sphere a Box a Cylinder etc 7 3 4 Create a Ball We will now add a ball to the simulation That ball will be modeled as a rigid body as shown in the figure 7 3 As Geometry nodes we will use Spheres In the scene tree view select the last node and add a Solid node using the Add button Similarly select
99. bots licenses can now be set up on an unlimited number of computers allowing you to use Webots seamlessly on any computer office home travel etc This new system relies on a license server located on Cyberbotics servers and accessible through an Internet connection If you would like to use Webots while not connected to the Internet you can transfer your Internet license from the server to your local computer for a limited duration After the expiration of this duration your license will be automatically transferred back to the license server Cyberbotics license servers are located in Switzerland on a highly reliable network featuring a 99 9 up time However if for some reason our servers would fail a security system will allow you to run Webots even in case of note server failure by connecting automatically to an alternate server located in the Cloud hosted on Google App Engine 1 5 1 Firewall configuration optional If you plan to use Webots behind an Internet firewall you should create two new rules in your firewall configuration to allow connections to the following servers e https www cyberbotics com port 443 e https webots license appspot com port 443 If you are using a proxy to access the Internet Webots will retrieve your system proxy configuration automatically note lnttp www cyberbotics com macosx 28 CHAPTER 1 INSTALLING WEBOTS 1 5 2 License agreement Please re
100. bots proposes to hands on revert the simulation choose Yes If everything is ok your robot should go forwards In the controllers directory of your project a directory containing the e puck_go_forward controller has been created The e puck_go_forward directory contains an e puck_go_forward binary file generated after note the compilation of the controller Note that the controller directory name should match with the binary name 7 3 TUTORIAL 2 MODIFICATION OF THE ENVIRONMENT 20 MINUTES 201 7 2 4 Conclusion We hope you enjoyed creating your first simulation You have been able to set up your environ ment to add a robot and to program it The important thing is that you learnt the fundamental concepts summarized below A Webots world is made of nodes organized in a VRML like tree structure A world is saved ina wbt file stored in a Webots project The project also contains the robot controllers which are the programs that define the robots behavior Robot controllers can be written in C or other languages C controllers have to be compiled before they can be executed Controllers are linked to robots via the cont roller fields of the robot nodes 7 3 Tutorial 2 Modification of the Environment 20 minutes In this tutorial we will teach you how to create simple objects in the environment The first step will be to create a ball which will interact with the environment We will tackle several concepts rel
101. buoyancy of the robot s body is also simulated using Archimedes principle 3 1 SAMPLES 67 Figure 3 8 soccer wbt 3 1 8 soccer wbt Keywords Soccer Supervisor DifferentialWheels label In this example two teams of simple Dif ferentialWheels robots play soccer A Super visor is used as the referee it counts the goals and displays the current score and the remaining time in the 3D view This example shows how a Supervisor can be used to read and change the position of objects 68 CHAPTER 3 SAMPLE WEBOTS APPLICATIONS CH Hes so Nicolas Uebelhart 30 11 2004 USAGE use the keyboard arrows space bar and r key to control the robots Figure 3 9 sojourner wbt 3 1 9 sojourner wbt Keywords Sojourner Passive joint planetary exploration robot keyboard IndexedFaceSet This is a realistic model of the Sojourner Mars exploration robot NASA A large obstacle is placed in front of the robot so that it is possible to observe how the robot manages to climb over it The keyboard can be used to control the robot s motion 3 1 SAMPLES 69 Figure 3 10 yamor wbt 3 1 10 yamor wbt Keywords Connector modular robots self reconfiguring robot In this example eight Yamor robot modules attach and detach to and from each other us ing Connector devices Connector devices are used to simulate the mechanical connections of docking systems In this example the robot modules go through a sequence of lo
102. bution We are to recreate the corresponding project based on its bare bones the world file WEBOTS_MODULES_PATH projects languages ros worlds joystick wbt the source file WEBOTS_MODULES_PATH projects languages ros controller catkin_ws src webots_joystick src webots_joystick_ node cpp and the ROS launcher fileWEBOTS_MODULES_PATH projects languages ros controller joy launch Note that joy launch is used inwebots_joystick_ node cpp to launch the ROS node joy_node as child process launch the joy ROS node int roslaunch fork if roslaunch 0 child process execlp roslaunch roslaunch joy launch NULL return 0 We will be done once we will have provided Webots with an executable file in WEBOTS_ MODULES_PATH projects languages ros controllers joystick whose name matches the controller directory name i e joystick which is also the name specified in Joystick wbt As we want this executable to be a ROS a node we will create and build a ROS package called webots_joystick and copy the resulting executable in WEBOTS_ MODULES_PATH projects languages ros controllers joystick 230 CHAPTER 7 TUTORIALS Prior to package construction we create and setup a catkin workspace from which we will run most of the build process through the cat kin_make command Create a project directory called my_ros with subdirectories worlds and controllers joystick Copy WEBOTS_MODULES_PATH project
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104. ce code for this controller is in the khepera_gripper directory 112 CHAPTER 3 SAMPLE WEBOTS APPLICATIONS Figure 3 52 khepera_gripper_camera wbt 3 5 20 khepera gripper camera wbt Keywords DifferentialWheels Gripper Camera Khepera In this example you can see a Khepera robot from K Team equipped with a gripper and a Cam era device The robot uses its gripper to grab a stick move a bit with it and drop it on the floor This behavior is repeated endlessly In this world the robot does not analyse the images it takes with its camera The source code for this controller is in the khepera_gripper directory 3 5 REAL ROBOTS 113 Figure 3 53 khepera_k213 wbt 3 5 21 khepera_k213 wbt Keywords DifferentialWheels DistanceSensor K213 linear Camera Khepera In this example you can see a Khepera robot from K Team equipped with a K213 Camera device This camera is a linear vision turret with greyscale images Using this device the robot is able to translate the information contained in the image into text and print this result in the Console window When you load this world the robot will not begin to move immediately It will give you enough time to read the explanations printed in the Console window concerning this world The source code for this controller is in the khepera_k213 directory 114 CHAPTER 3 SAMPLE WEBOTS APPLICATIONS Figure 3 54 khepera_pipe wbt 3 5 22 khepera pipe wbt Keywords DifferentialWheels
105. celeration ApS 0 acos AA Be SO TO SD OR 23 1 4 Tnstallation procedure 2 s sa th ee eek e e Gae ua e Gates 24 eed L So Be eee EERE RE REE ROR E Re RE EES 24 142 WIADOWS sae se m koe m dog Re bos RR Oe ae ee ae We Bet 26 IES MacOSX 6 4 64 4 GEOR ELE AA 27 1 5 Webots license Systemy gt ez grasas eg ede eee SER RSE ee a 27 1 5 1 Firewall configuration optional a 27 1 5 2 License dpreement cici doci IN 28 Las ALIAS eUD a e RA A tS es BS BO BOW Bt a 28 1 5 4 License administration o s sossen ee dat ta See eee es 28 1 5 5 Module download folder 2 222 4 24 224 a 28 1 6 Classroom license ESB e ocs sociis ocs mocs ock d ank d aok ee eS 29 8 CONTENTS LAT 29 10 2 AS s oes eee ee eRe ee ee eM eM eA OS 31 16 3 Homework cierre Ree SEE eRe AP ERE EES 31 1 6 4 Using Webots without Internet connection 32 1 7 Translating Webots to your own language 32 2 Getting Started with Webots 33 2 1 Introduction to Webots 24 426 oe ae ee ee ee Ow eee Ee eee ew ee 33 211 Whatis WEG lt secs socs ados e OR S ark G ane Wwe Paa 33 2 1 2 Whatcan Ildo with Webots 22244 se moleci eneth oleon enh a ions 33 2 1 3 What do I need to know to use Webots 34 2 1 4 Webots simulation aao e 34 215 Whatisawond o ea ae te ee eed ee ee teases a a a Go 35 21 6 Whatisacontroller oo c sea ose eee ee RSE deade a ELA 35 21 7 Whatisa SUpervisor e oce a a doa oe goci a aoe a ao
106. click on the Install button If a previous version of Webots is already installed then the text on the button could be different like Upgrade or Reinstall Alternatively the DEB package can also be installed using dpkg or gdebi with the root privileges For 32 bit systems dpkg i webots_8 3 2_1386 deb apt get f install or gdebi webots_8 3 2_i386 deb For 64 bit systems dpkg i webots_8 3 2_amd64 deb apt get f install or gdebi webots_8 3 2_amd64 deb 1 4 2 Windows 1 Download the webot s 8 3 2 setup exe installation file from our web site 2 Double click on this file 3 Follow the installation instructions It is possible to install Webots silently from an administrator DOS console by typing webots 8 3 2_setup exe SILENT or webots 8 3 2_setup exe VERYSILENT If you observe 3D rendering anomalies or Webots crashes it is strongly recommend to upgrade your graphics driver http www cyberbotics com windows 1 5 WEBOTS LICENSE SYSTEM 27 1 4 3 Mac OS X 1 Download the webot s 8 3 2 dmg installation file from our web site 2 Double click on this file This will mount on the desktop a volume named Webots con taining the Webot s folder 3 Move this folder to your Applications folder or wherever you would like to install Webots 1 5 Webots license system Starting with Webots 8 a new license system was introduced to facilitate the use of Webots which replaces the previous system We
107. clude special robot models e g NAO DARwIn OP e puck Thymio 2 etc object models e g cardboard box wooden box etc environment models e g robot soccer field programming libraries programming languages e g C C Matlab Python interfaces to third parties software or hardware etc They are all described on Cyberbotics web site 1 1 4 Webots licences overview The following table summarizes the main differences between Webots PRO Webots EDU and Webots MOD Webots feature PRO EDU MOD Supervisor capability yes no no Physics plug in programming yes no no Fast simulation mode yes no no Robot and environment modelling yes yes no Robot programming yes yes yes no 1 Transfer to real robots yes yes yes no 1 Multi platform Windows Mac amp Linux yes yes yes Floating licenses yes yes yes One year Premier Service included yes yes yes Table 1 1 Webots licenses summary 1 refer to specific module description 1 2 System requirements The following hardware is required to run Webots e A fairly recent PC or Macintosh computer with at least a 2 GHz dual core CPU clock speed and 2 GB of RAM is a minimum requirement A quad core CPU is however recommended e An nVidia or AMD formerly ATI OpenGL minimum version 2 1 capable graphics adapter with at least 512 MB of RAM is required We do not recommend any other graph ics adapters inclu
108. code from Webots examples to Visual C it is highly recom mended to change the source file extension from c to cpp The reason is that Webots examples are written for the gcc compiler which uses a more modern version of the C language than Visual C By changing the file extension to cpp you will instruct Visual C to compile the file in C mode TP which is more tolerant with gcc code If you don t do it you may run into error messages like these MyController c 24 error C2275 WbDeviceTag illegal use of this type as an expression MyController c 24 error C2146 syntax error missing before identifier 1ir0 150 CHAPTER 5 DEVELOPMENT ENVIRONMENTS 4 Now we can set up the project configuration for Webots Select the Project gt Properties menu In the Property Pages in the Configuration Properties enter following configura tion C C gt General gt Additional Include Directories C Program Files Webots include controller c This will tell Visual C where to find Webots C API h files By default Visual C places the exe file in a Debug or Release subdirectory How ever order to be executed by Webots the exe file must be placed directly at the root of the MyController directory So in this example the exe should be there MyProject controllers MyController MyController exe Consequently the linker out put file should be configured like this Linker gt
109. communication protocol to dialog with the real robot devices The remote control library is initialized when an entity calls the wo_robot_set_mode lib Controller function This entity is typically libRobotWindow because it s quite convenient to use the GUI to initialize the communication i e entering the IP address of the robot etc There are two entry points to the remote control library e bool wbr_init Worinterface xri This function is called by libController to initialize the remote control library It is called after the first wo_robot_set mode call The aim of this function is to map the func tions given into the WorInterface structure with functions inside the remote control library e void wbr cleanup This function is called by libController to cleanup the library The WorInterface structure has several functions mandatory which have to be mapped to let the remote control library run smoothly Here they are e bool wbr_start void arg This function is called when the connection with the real robot should start The return value of this function should inform if the connection has been a success or not The argu ment matches with the argument given to wo_robot_set_mode when initializing the remote control As the robot window library is often responsible in calling wo_robot set mode the structure passed between them should match e void wbr_ stop This function is called when
110. compiz desktop effects are on Also these visual effects may cause some display bug where the main window of Webots is not properly refreshed Hence on Ubuntu or other Linux we recommend to deactivate the desktop effects You can easily disable them using some tools like Compiz Config Settings Manager or Unity Twerk Tool 3http www nvidia com http www amd com Shttp www nvidia com Shttp www amd com 24 CHAPTER 1 INSTALLING WEBOTS 1 4 Installation procedure Usually you will need to be administrator to install Webots Once installed Webots can be used by a regular unprivileged user To install Webots please follow this procedure 1 Uninstall completely any old version of Webots that may have been installed on your computer previously 2 Install Webots for your operating system as explained below After installation the most important Webots features will be available but some third party tools such as Java Python or MATLAB may be neces sary for running or compiling specific projects The chapter 4 covers the set up of these tools note 1 4 1 Linux Webots will run on most recent Linux distributions running glibc2 11 1 or earlier This includes fairly recent Ubuntu Debian Fedora SuSE RedHat etc Webots comes in two different package types deb and tar bz2 tarball The deb package is aimed at the latest Ubuntu Linux distribution whereas the tarball package includes many dependenc
111. cs web site Create this account if needed log in and visit the Profile page of this account Copy the Alternate password for Webots 8 This password allows students to use Webots but not to log in this user account It looks like JoebgAGRgFtkf8QHiWoHXIUnI 98 Give this e mail address and alternate password to your students to allow them to log in Webots using your licenses but they won t be able to log in the web page Multiple user accounts The multiple user accounts license requires that you have the list of e mail addresses of the students to whom you want to grant access to your Webots licenses You will be able to limit the number of simultaneous instances of Webots used per student to 1 so that a single student cannot use multiple licenses simultaneously Hence a single student cannot prevent the others from using Webots Log in to your Webots user account using your license administration credentials e g the user account which was used to activate your Webots licenses Create a new user pack from the administration page and call it Students Grant access to all your 20 Webots EDU license tick boxes Set the concurrency value to to prevent a single user to use multiple instances of Webots at the same time Type or copy paste the list of student e mail addresses in the users text area Press the apply button The e mail addresses which are not already regis
112. cumulate er rors Therefore any modification of the world should be performed in that order pause revert modify and save the simulation theory As we don t need to create the e puck robot from scratch we will just have to import a special E puck node in fact a PROTO node as the RectangleArena we introduced before A PROTO is an abstract assemblage of several nodes PROTO nodes are defined in separate proto but this will be explained in more details later For now consider the E puck node as a black box that contains all the necessary nodes to define a e puck robot Select the last node of the scene tree view called RectangleArena In order to add the E puck node click on the Add button at the top of the scene tree view In the open dialog box and choose PROTO Webots gt hands on robots gt e puck gt E puck DifferentialWheels Then save the simulation 198 CHAPTER 7 TUTORIALS Now if you run the simulation the robot moves that s because the robot uses a default controller with that behavior Please pause and revert the simulation note before going on You can change the robot s position in the 3D view using the translation and rotation handles see subsubsection 2 4 3 Alternatively the following keyboard shortcuts are available SHIFT left clicking drag to move the robot parallel to the floor note SHIFT mouse wheel to move the robot up or down Finally it i
113. d 6dd5 in _IO str_overflow_internal from lib tls libc so 6 1 0x00cd596f in _10_default_xsputn_internal from lib tls libc so 6 148 CHAPTER 5 DEVELOPMENT ENVIRONMENTS 2 Ox00cca9cl in _10_padn_internal from lib tls libc so 6 3 Ox00cbl7ea in vfprintf from lib tls libc so 6 4 Ox00ccb9cb in vsprintf from lib tls libc so 6 5 Ox00cb8d4b in sprintf from lib tls libc so 6 6 0x08048972 in run ms 0 at soccer_supervisor c 106 7 0x08048b0a in main at soccer_supervisor c 140 By examining carefully the call stack you can locate the source of the error In this example we will assume that the sprintf function is OK because it is in a system library Therefore it seems that the problem is caused by an illegal use of the sprintf function in the run function The line 106 of the source file soccer_supervisor c must be examined closely While the controller is still in memory you can query the values of some variables in order to understand what happened For example you can use the frame and print commands gdb frame 6 6 0x08048953 in run ms 0 at soccer_supervisor c 106 106 sprintf time_string 02d 02d int time 60 int time 60 gdb print time_string S1 0x0 The frame command instructs the debugger to select the specified stack frame and the print command prints the current value of an expression In this simple example we clearly
114. d click on the Webots icon 2 2 4 Command Line Arguments Following command line options are available when starting Webots from a Terminal Linux Mac or a Command Prompt Windows SYNOPSIS webots options worldfile OPTIONS minimize minimize Webots window on startup mode lt mode gt choose startup mode overrides application preferences argument lt mode gt must be one of pause realtime run or fast Webots PRO is required to use mode run or mode fast help display this help message and exit sysinfo display information of the system and exit version display version information and exit uuid display the UUID of the computer and exit 2 2 STARTING WEBOTS 37 stdout redirect the controller stdout to the terminal stderr redirect the controller stderr to the terminal disable modules download skip the check for module updates force modules download automatically download module updates if any at startup start streaming server starts the Webots streaming server Webots PRO is required key value parameters may be given as an option port 1234 starts the streaming server on port 1234 monitorActivity prints a dot on stdout every 5 seconds disableStandardStreamsRedirection disables the streaming of the standard output and error streams log performance lt file path gt lt steps count gt
115. d the robot collapses This example illustrates how to build a simple articulated robot and also how to turn off motor power 86 CHAPTER 3 SAMPLE WEBOTS APPLICATIONS Figure 3 27 force_control wbt 3 3 3 force control wbt Keywords Force control linear motor spring and damper This world shows two boxes connected by a LinearMotor Here the purpose is to demon strate the usage of the wb_motor_set_force function to control a LinearMotor with a user specified force In this example wo_motor_set_force is used to simulate the effect of a spring and a damper between the two boxes When the simulation starts the motor force is used to move the boxes apart Then the motor force is turned off and boxes oscillate for a while now according to the spring and damping equations programmed in the controller 3 3 HOW TO 87 Figure 3 28 inverted_pendulum wbt 3 3 4 inverted_pendulum wbt Keywords Inverted pendulum PID LinearMotor In this example a robot moves from left to right in order to keep an inverted pendulum upright This is known as the Inverted Pendulum Problem and it is solved in our example by using a PID Proportional Integral Differential controller 88 CHAPTER 3 SAMPLE WEBOTS APPLICATIONS Figure 3 29 physics wbt 3 3 5 physics wbt Keywords Physics plugin OpenGL drawing flying robot Emitter Receiver In this example a robot flies using a physics plugin This plugins is an example of e how t
116. d then interpreted by a Java Virtual Machine The source files and binary files of each controller are stored together in a controller directory A controller directory is placed in the controllers subdirectory of each Webots project 2 1 7 What is a Supervisor The Supervisor is a privileged type of Robot that can execute operations that can normally only be carried out by a human operator and not by a real robot The Supervisor is normally associated with a controller program that can also be written in any of the above mentioned programming languages However in contrast with a regular Robot controller the Supervisor controller will have access to privileged operations The privileged operations include simulation control for example moving the robots to a random position making a video capture of the simulation etc 36 CHAPTER 2 GETTING STARTED WITH WEBOTS 2 2 Starting Webots The first time you start Webots it will open the Welcome to Webots menu with a list of possible starting points 2 2 1 Linux Open a terminal and type webot s to launch Webots 2 2 2 MacOS X Open the directory in which you installed the Webots package and double click on the Webots icon 2 2 3 Windows On Windows 10 and Windows 7 open the Start menu go to the Program Files gt Cyberbotics menu and click on the Webots 8 3 2 menu item On Windows 8 open the Start screen scroll to the screen s right until spotting the Cyberbotics section an
117. dInfo FPS This field represents the maximum rate at which the 3D display of the main windows is refreshed With a lower value the simulation becomes faster but more flickering With a higher value the simulation becomes slower but less flickering Try changing the value of WorldInfo optimalThreadCount This field specifies how many threads are used to simulate the physics of the world Depending on the world you can get a better performance by reducing or increasing this value In general it is better to have a low number of threads for simple worlds and a bigger number of threads for complex worlds that include several robots physically independent from each other Disable unnecessary shadows Webots uses a lot of CPU GPU power to compute how and where the objects shadows are cast But shadows are irrelevant for most simulation unless they should explicitly be seen by Cameras Unnecessary shadows can be disabled by unchecking the castShadows field of light nodes PointLight SpotLight orDirectionalLight Simplify your simulation by removing unnecessary objects In particular try to minimize the number of Physics nodes Avoid using a Solid nodes when a Transform or a Shape would do the trick Simplify the boundingOb jects to increase the speed of the collision detection Replace complex primitives like Cylinder IndexedFaceSet and ElevationGrid by simpler primitives like Sphere Capsule Box and Plane Avoid usin
118. de lt webots xyz h gt where xyz represents the name of a Webots node in lowercase Like with any regular C code it is also possible to include the standard C headers e g include lt stdio h gt A call to the initialization function wob_robot_init is required before any other C API function call This function initializes the communication between the controller and Webots Note that wb_ robot_init exists only in the C API it does not have any equivalent in the other supported programming languages Usually the highest level control code is placed inside a for or a while loop Within that loop there is a call to the wo_robot_step function This function synchronizes the controller s data with the simulator The function wo_robot_step needs to be present in every controller and it must be called at regular intervals therefore it is usually placed in the main loop as in the above example The value 32 specifies the duration of the control steps i e the function wb_ robot_step shall compute 32 milliseconds of simulation and then return This duration specifies an amount of simulated time not real wall clock time so it may actually take 1 millisecond or one minute of CPU time depending on the complexity of the simulated world Note that in this Hello World example the while loop has no exit condition hence the return statement is never reached It is usual to have an infinite loop like this in the controller code
119. de of the scene tree such as Robot LED etc or either utility classes such as Motion ImageRef etc A complete description of these functions can be found in the reference guide while the instructions about the common way to program a Java controller can be found in the chapter 6 4 5 2 Java and Java Compiler Installation In order to develop and run Java controllers for Webots it is necessary to have the Java Develop ment Kit JDK version 1 7 4 5 USING JAVA 129 Installation Instructions The Java Development Kit JDK can be downloaded for free from the Sun Developer Network Make sure you choose the most recent release and the Standard Edition SE of the JDK 7 For Windows make also sure you have selected the 64 bit version since webots is incompatible with the 32 bit version Then follow the installation instructions attending the package The java command is the Java Virtual Machine JVM it is used for executing Java controllers in Webots The javac command is the Java compiler it is used for compiling Java controllers in Webots text editor These commands should be accessible from a terminal If it is not the case this can be done by modifying your PATH environment variable On Mac the JDK installer should do this automatically On Linux you can set the PATH by adding this line to your bashrc or equivalent file export PATH usr lib jvm java XXXXXX bin S PATH Where java XXXXXX should correspond to the act
120. detail controller programming We invite you to read carefully this section before going on 7 6 Tutorial 5 Compound Solid and Physics Attributes 15 minutes The aim of this chapter is to explore in more detail the physics simulation by creating a solid with several bounding objects a dumbbell made of two spheres and one cylinder The expected result is depicted in figure 7 11 7 6 TUTORIAL 5 COMPOUND SOLID AND PHYSICS ATTRIBUTES 15 MINUTES 219 und_solid wbt Webots PRO 7 4 1 Simulation View REC0O BO Ib p W W 0 00 00 000 ooox E gt DEF WALL_3 Solid gt DEF WALL _4 Solid Y DEF DUMBBELL Solid translation 0 2 0 1 0 1 8 rotation 100 1 5708 scale111 children name solid model description contactMaterial dumbbell boundingObject USE GO Y physics Physics locked FALSE E translationStep 0 01 El rotationStep 0 261799 Solid O Node Mass DEF DUMBBELL USE count 0 Transform to lt none gt Export Figure 7 11 Expected result at the end of the tutorial about compound solids 7 6 1 New simulation Start from the results of the previous tutorial and create a new simulation called compound_solid wbt by using the menu File gt Save World As hands on 7 6 2 Compound Solid It is possible to build Solid nodes more complex than what we have seen before by aggregating Shape nodes In fact both the physical and the gr
121. ding Intel graphics adapters as they often lack a good OpenGL support which may cause 3D rendering problems and application crashes Nevertheless in some 1 3 VERIFYING YOUR GRAPHICS DRIVER INSTALLATION 21 cases the installation of the latest Intel graphics driver can fix such problems and let you use Webots However we don t provide any guarantee on this For Linux systems we rec ommend only nVidia graphics cards Webots works well on all the graphics cards included in fairly recent Apple computers It is strongly advised to try the 30 day trial version of Webots on your computer systems to ensure they are compatible before you buy The following operating systems are supported e Linux Webots is ensured to run on the latest Ubuntu Long Term Support LTS release currently version 14 04 But it is also known to run on most recent major Linux distribu tions including RedHat Mandrake Debian Gentoo SuSE and Slackware We recom mend using a recent version of Linux Webots is provided for Linux 64 x86 64 systems Since Webots 8 1 0 the Linux 32 i386 version is no longer provided Webots doesn t run on Ubuntu version eariler than 12 04 e Windows Webots runs on Windows 10 64 bit Windows 8 1 64 bit Windows 8 64 bit and Windows 7 64 bit It is not supported on 32 bit versions of Windows and on old versions including Windows Vista XP NT4 or 2000 e Macintosh Webots runs on Mac OS X 10 11 El Captan and 10 10 Yosemi
122. e MyController jar and finally lib MyLibrary jar note 6 2 Supervisor Programming The programming examples provided here are in C but same concepts apply to C Java Python Matlab 168 CHAPTER 6 PROGRAMMING FUNDAMENTALS 6 2 1 Introduction The Supervisor is a special kind of Robot In object oriented jargon we would say that the Supervisor class inherits from the Robot class or that the Supervisor class extends the Robot class The important point is that the Supervisor node offers the wo_supervi sor_ functions in addition to the regular wo_robot_ functions These extra functions can only be invoked from a controller program associated with a Supervisor node not with a Robot or a DifferentialWheels node Note that Webots PRO is required to create Supervisor nodes or use the wo_supervisor_x functions In the Scene Tree a Supervisor node can be used in the same context where a Robot node is used hence it can be used as a basis node to model a robot But in addition the wo_super visor functions can also be used to control the simulation process and modify the Scene Tree For example the Supervisor can replace human actions such as measuring the distance travelled by a robot or moving it back to its initial position etc The Supervisor can also take a screen shot or a video of the simulation restart or terminate the simulation etc It can read or modify the value of every fields in the Scene Tr
123. e 2 1 1 10 Please note that Webots must not be launched as root when using any world containing naoqisim otherwise Choregraphe won t be able to send instructions to the robot in Webots http www aldebaran robotics com http www aldebaran robotics com Shttp www robotstadium org 246 CHAPTER 8 ROBOTS Start Webots and open this world file WEBOTS_MODULES_PATH projects robots aldebaran worlds nao wbt You should see a red Nao in an empty environment If the simulation is paused then please start it by pushing the Real time button in Webots The camera images in Webots small purple viewports should reflect what the robot sees Several lines of text information corresponding to the output of NAOqi should be printed to Webots console Now you can start Choregraphe with the no naoqi option Please make sure the Choregraphe version matches the NAOgqi version printed in Webots console In Choregraphe choose the menu Connection gt Connect to Then in the list select the NAOqi that was started by Webots on you local machine it will have the port number 9559 unless you change it Note that the NAOqi will not appear in the list if the simulation was not started in Webots If the simulation was started but the robot still doesn t appear in the list force the IP and port to 127 0 0 1 and 9559 in Choregraphe and then press connect At this point a Nao model matching the Webots model should appear in Choregraphe Now in C
124. e IPR robots use the same controller whose source code is in the ipr_serial directory This particular example uses in addition to this controller a client program which coordinates the movements of the robots The source code for this client is in the ipr_serial client ipr_collaboration c file 104 CHAPTER 3 SAMPLE WEBOTS APPLICATIONS Figure 3 44 ipr_cube wbt 3 5 12 ipr_cube wbt Keywords Robot node robotic arm TCP IP client program IPR IndexedFaceSet Rotational Motor active joint In this example an IPR robots from Neuronics moves a small red cube onto a bigger one All the IPR robots use the same controller whose source code is in the ipr_serial directory This example also uses a client program which drives the movements of the robot The source code of this client is in the ipr_serial client ipr_cube c file 3 5 REAL ROBOTS 105 Figure 3 45 ipr_factory wbt 3 5 13 pr factory wbt Keywords Robot node Supervisor conveyor belt robotic arm TCP IP client program IPR IndexedFaceSet RotationalMotor active joint In this example two IPR robots from Neuronics take industrial parts from a conveyor belt and place them into slots One of the robots detects the objects using an infrared sensor on the conveyor belt while the other one waits All the IPR robots use the same controller whose source code is in the ipr_serial directory This example also uses a client program which coordinates the movements o
125. e MATLAB desktop The keyboard stops the execu tion of the controller and gives control to the keyboard K gt gt prompt Then MATLAB opens your controller m file in its editor and indicates that the execution is stopped at the keyboard command After that the controller m file can be debugged interactively 1 e it is possible to continue the execution step by step set break points watch variable etc While debugging the current values of the controller variables are shown in the MATLAB workspace It is possible to continue the execution of the controller by typing return at the K gt gt prompt Finally the execution of the controller can be terminated with Ct r1 C key combination Once the controller is terminated the connection with Webots remains active Therefore it be comes possible to issue Webots commands directly at the MATLAB prompt for example you can interactively issue commands to query the sensors etc gt gt wb_differential_wheels_set_speed 600 600 gt gt wb_robot_step 1000 6 6 CONTROLLER PLUGIN 183 gt gt wb_gps_get_values gps ans 0 0001 0 0030 0 6425 gt gt It is possible to use additional keyboard statements in various places in your m controller So each time MATLAB will run into a keyboard statement it will return control to the K gt gt prompt where you will be able to debug interactively At this point it is also possible to restart the controller by callin
126. e Oe ee Oe ee A We a ard 204 130 ADEP USE mechanism lt c 3 4 06 42503 erin eG bk edie aoe i 204 Gai AUS a Rg e ig So OE BO Be A 205 ER cats we ae es be ae ee ew ew e i O S 207 A sorp sop Beye antak a Se ee ea ree ee ee 207 74 Tutorial 3 Appearance 15 minutes 24 2 ei eee eee ed eed ees 208 T amp A Mew Simulation o e via oe eee Ce REE ESR eS EY OSS 208 EL VACHS gt si eRe RASHEED ES eS 208 7 4 3 Modify the Appearance of the Walls 2254 2h eee eee ee 209 7144 Adda Texture tothe Ball oo 524 consensos 209 745 Rendering Options 4 25 e eek ad a KE ES 210 7AM Conclusi n 2s os 444 5445 arras 210 7 5 Tutorial 4 More about Controllers 20 minutes 210 7 5 1 New World and new Controller 211 16 CONTENTS 7 5 2 Understand the e puck Model 4 kek bee eR ee RO eS 211 too POBLA CONOS o ss ese mas ee eK eM EKO OS 212 7 5 4 The Controller Code 25 244 22235e8 He ev eee ake ud ees 216 Vem CONSIGN s se a a me hoes dooce Soe ce ees oe sd ee e ar 218 7 6 Tutorial 5 Compound Solid and Physics Attributes 15 minutes 218 76 1 New Simulation pa eso ee ee eee EEE SEE EH eR AA 219 762 epee A 219 TOS Physics ARTIDUIES ociosas ee eee aa 220 164 The Rotation Field scsi ira aa a 221 7635 Howto choose bounding Objects lt s is A A 4S 221 TRO COM cidad ita 222 76 7 b siclimesStep ERP and CFM 06 rar ra a ee 222 16 8 Mimor physics Parameters cs A a SHR SERS
127. e Soy pOr 35 2 2 Starine WEIS Los a eA Re aa g ER A 36 ged AN 36 Pa MCSA enoi aena A A DA BRS ew Se OSH L a 36 223 Windows 2255265625048 4284 a eh a a Gaa es a a a i 36 2 2 4 Command Line Arguments 2 lt s se sse aos e RR 36 2 The User Interface sors sor dioa Sok aie a n a eS ew A MS 38 231 File Men s e ade edea aa e a a a 44844444 38 292 UI soss eae a a e ae Be Be ARA Os 41 Cee MEW IIS ee o A AS Boe oe Se Se Ee A Se 41 234 Simulation Menu ooo 238 h 054404 0044 43 233 Buld MI sog ec ke eS ee SO ee he Se Be Be Boe hes Bes 44 230 ODO lt gt es beck ex Pek a Eee Se SSR ES OSS 44 2 37 Tools Men e ace ceea cs ede edu sea hd che ass eeddrs 45 23 8 Wizards Menu o e eg sogana manganesa gioa gaia aih ai 45 239 Hes Me eer re ech ee eh ee Be BSR Se BSS Ow a 46 2310 Maim toolbaf sss eke ee oe See ee A ORS Oe ee 46 CONTENTS 9 2 311 Speedometer and Virtual TIME gt lt e sos e bos asom oa ocs atok sa Oars 47 24A NM 47 2 4 1 Selecting an object gt o 2 25242 22 bee eee eee ERE ERR EES 47 24 2 Navigati n IN TNE SUCHE s si 20009 scia OS ook eS ee ew OS 48 2 4 3 Movmg A solid object ica ee ce eee a Ree Ewe OS 48 2 4 4 Applying a force to a solid object with physics 49 2 4 5 Applying a torque to a solid object with physics 50 2 4 6 Moving and resizing Overlays 2 6 ia se eee eee bee eee ee 50 2 4 7 Show Camera and Display images in separate window 50 29 The Scone TEE e g a
128. e a sufficient introduction At the end of the chapter links to further robotics algorithmics are given 7 5 1 New World and new Controller Save the previous world as collision_avoidance wbt hands on Create a new C controller called e puck_avoid_collision using the wizard Modify the controller field of the E puck node in order to link it hands on to the new controller 7 5 2 Understand the e puck Model Controller programming requires some information related to the e puck model For doing the collision avoidance algorithm we need to read the values of its 8 infra red distance sensors located around its turret and we need to actuate its two wheels The way that the distance sensors are distributed around the turret and the e puck direction are depicted in figure 7 9 The distance sensors are modeled by 8 DistanceSensor nodes in the hierarchy of the robot These nodes are referenced by their name fields from ps0 to ps7 We will explain later how these nodes are defined For now simply note that a DistanceSensor node can be accessed through the related module of the Webots API through the webots distance_sensor h include file The values returned by the distance sensors are scaled between 0 and 4096 piecewise linearly to the distance while 4096 means that a big amount of light is measured an obstacle is close and 0 means that no light is measured no obstacle In the same way the e puck root node
129. e designers of the successful Khepera robot The hardware and software of e puck is fully open source pro viding low level access to every electronic device and offering unlimited extension possibilities The official e puck web site provides the most up to date information about this robot E puck is also available for purchase from Cyberbotics Ltd 8 1 1 Overview of the robot E puck was designed to fulfill the following requirements Elegant design the simple mechanical structure electronics design and software of e puck is an example of a clean and modern system Flexibility e puck covers a wide range of educational activities offering many possibilities with its sensors processing power and extensions Simulation software e puck is integrated with Webots simulation software for easy pro gramming simulation and remote control of the physical robot User friendly e puck is small and easy to setup on a tabletop next to a computer It doesn t need any cables providing optimal working comfort Robustness and maintenance e puck is resilient under student use and is simple to repair e Affordable the price tag of e puck is friendly to university budgets E puck is equipped with a large number of devices as summarized in table 8 1 Inttp www e puck org 235 236 CHAPTER 8 ROBOTS Figure 8 1 The e puck robot at work 8 1 2 Simulation model The e puck model in Webots is depicted in figure 8 2 This model
130. e eas 276 Chapter 1 Installing Webots This chapter explains how to install Webots and configure your license rights 1 1 Webots licenses The Webots licenses comes in three different flavors including Webots PRO Webots EDU and Webots MOD They differ by the features and price These different versions are described in this section The features available in the different versions are summarized in table 1 1 1 1 1 Webots PRO Webots PRO is the most powerful version of Webots It is designed for research and development projects Webots PRO includes the possibility to create supervisor processes for controlling robotics experiments an extended physics programming capability and a fast simulation mode faster than real time A 30 day trial version of Webots PRO is available from Cyberbotics web site 1 1 2 Webots EDU Webots EDU is tailored for classrooms Students learn how to model robots create their own environments and program the behavior of the robots using any of the supported programming languages To validate their models they can optionally transfer their control programs to real robots A 30 day trial version of Webots EDU is available upon request 19 20 CHAPTER 1 INSTALLING WEBOTS 1 1 3 Webots MOD Webots MOD is a special license mode in which the simulation software comes free of charge and the users pay only for the modules they need Various modules are available for purchase at different price tags They in
131. e exercises can be reproduced by adding a Thymio2Ball1 node in your world The ball can be slightly moved by applying a force on it ALT mouse left click An example of this is located there see the figure 8 13 WEBOTS_MODULES_PATH projects robots thymio worlds thymio2_ball wbt 8 4 Using the Pioneer 3 AT and Pioneer 3 DX robots 8 4 1 Pioneer 3 AT In this section you will learn how to use Webots simulation model of the Pioneer 3 AT robot figure 8 14 Overview of the robot The Pioneer 3 AT robot is an all purpose outdoor base used for research and prototyping ap plications involving mapping navigation monitoring reconnaissance and other behaviors It provides a ready to use set of devices listed in table 8 6 Mhttps aseba wikidot com en thymioballeinverse 254 CHAPTER 8 ROBOTS Figure 8 14 Pioneer 3 AT a ready to use all terrain base Feature Description Dimensions 508 mm long 497 mm large 277 mm high Weight 12 kg operating playload of 12 kg on floor Batteries 2 4 hours up to 3 lead acid batteries of 7 2 Ah each 12 V Microcontroller 32 digital inputs 8 digital outputs 8 analog inputs 3 serial extension ports O Skid steering drive Turn radius 0 cm swing radius 34 cm max traversable grade 35 Speed Max forward backward speed 0 7 m s Rotation speed 140 deg s Table 8 6 Pioneer 3 AT features More information on the specifications and optional devices is
132. e puck is to cross compile your code and to upload it on the e puck For using this feature your code has to be written in C and to use the C Webots API Moreover you need to define a specific Makefile called Makefile e puck in the controller directory This Makefile must include the following file include WEBOTS_MODULES_PATH projects robots e puck transfer libepuck Makefile include Thanks to this it is possible to cross compile with Webots by using the Build gt Cross compile menu item of the text editor Note that the Upload to e puck robot button of the e puck control window allows you to upload a file generated by the cross compilation extended by hex on the e puck robot An example of cross compilation is given in the WEBOTS_MODULES_PATH projects robots e puck controllers e puck_cross compilation subdirectory of your Webots di rectory Cross compilation issues on Linux 64 bit When cross compiling on Linux 64 bit it may occur such kind of error 8 2 USING THE NAO ROBOT 245 bin sh 1 pic30 elf gcc not found make xxx e puck_cross compilation pic30 o Error 127 This error can be fixed simply by installing the following packets from a terminal sudo apt get install gcc 4 6 base i386 libgcc1 1386 libc6 1386 8 2 Using the Nao robot 8 2 1 Introduction The Nao robot is a humanoid robot developed by Aldebaran Robotics This section explains how to use Nao robot simulated in Webots toge
133. e sensors like double val distanceSensor getValue Process sensor data here Enter here functions to send actuator commands like led set 1 Enter here exit cleanup code public si MyRobot robot run Cyberbotics webots controller x step TIME_STEP 1 tatic void main String args t robot new MyRobot 6 5 MATLAB 181 6 4 5 Python Example 1 from controller import x 2 3 class MyRobot Robot 4 def run self 3 led self getLed ledName 6 distanceSensor self getDistanceSensor distanceSensorName 2 7 distanceSensor enable 32 8 9 while self step 32 1 10 Read the sensors like 11 val distanceSensor getValue 12 13 Process sensor data here 14 15 Enter here functions to send actuator commands like 16 led set 1 15 18 Enter here exit cleanup code 19 20 robot MyRobot 21 robot run 6 5 Matlab The MATLAB API for Webots is very similar to the C API The functions names are identical only the type and number of parameters differs slightly in some cases The MATLAB functions and prototypes are described in Webots Reference Manual Note that unlike with the C API there are no wb_robot_init and wb_robot_cleanup functions in the MATLAB API The necessary initialization and cleanup are automatically carried out respectively bef
134. e simulation is We recommend values between 8 and 6 for a regular use of Webots It s more difficult to explain the behavior of the ERP and CFM fields These values are directly used by the physics engine to determine how the constraints are solved The default values are well defined for a regular use of Webots We recommend to read the Reference Manual and the documentation of ODE physics engine used in Webots to understand completely their purpose 7 6 8 Minor physics Parameters There are also other physics parameters which are less useful in a regular use of Webots A complete description of these parameters can be found in the Reference Manual Remark simply that the Physics WorldInfo and ContactProperties nodes contains other fields http ode wiki org wiki index php title Manual 7 7 TUTORIAL 6 4 WHEELS ROBOT 223 Search in the Reference Manual how to add a linear damping on all the ob jects how to unset the auto disable feature and how to use the inertia matrix hands on 7 6 9 Conclusion You are now able to build a wide range of solids including those being composed of several rigid bodies You know that a Geometry node can be moved and rotated if it is included in a Transform node You are aware about all the physics parameters allowing you to design robust simulations The next step will be to create your own robot You can test your skills by creating common objects such as a table 7 7 Tutorial 6
135. e wb_robot_step call is the key point to understand how the different entry points of the robot window plugin are called pseudo code 186 CHAPTER 6 PROGRAMMING FUNDAMENTALS wb_robot_step wow_write_actuators wbw_pre_update_gui write_request_to_webots_pipel wow_update_gui returns when something on the pipe read_request_to_webots_pipe wbw_read_sensors Da Una As the Qt libraries are included in Webots used by the Webots GUI and all our samples are based on it we recommend to choose also this framework to create your GUI The Make file include mentioned above allows you to efficiently link with the Qt framework embed ded in Webots The Webots pipe handle integer id is available in the WEBOTS_PIPE_IN environment variable The Qt utility library helps you to initialize Qt correctly pipe window visibility Refer to the next section for more information related with this library If the robot window cannot be loaded bad path bad initialization etc a generic robot win dow is opened instead This generic robot window displays several sensors and actuators The source code of this robot window is a good demonstrator of the robot window plugin abilities All the source code is located there WEBOTS_HOME resources projects plugin s robot_windows generic_window Other samples can be found WEBOTS_MODULES_PATH projects robots e puck plugins robot_windows bot studio WEBO
136. ebots capabilies through a series of examples The OpenGL Information menu item gives you information about your current OpenGL hard ware and driver It can be used to diagnose rendering problems The remaining menu items bring up various information as indicated in the form of HTML pages PDF documents etc 2 3 10 Main toolbar The main toolbar contains items for editing the world and the speedometer see subsection sub section 2 3 11 other than shortcuts to items of the File Simulation and View menus Edit actions always apply on the selected object that is highlighted both in the 3D window and in the Scene Tree Cl Hide Show Scene Tree shows or hides the Scene Tree and resizes the 3D window conse quently End Cut Cuts the selected object da Note that the first three nodes of the Scene Tree WorldInfo Viewpoint and Back ground cannot be cut copied or pasted One single instance of each of these nodes must be present in every Webots world and in that precise order Copy Copies the selected object Paste Pastes the copied or cut object o Add Adds a node or an object For nodes this triggers a dialog that will let you choose a node type from a list The new node is created with default values that can be modified af terwards You can only insert a node suitable for the corresponding field The dialog also gives the possibility to load a previously exported node by clicking on the Import button
137. ectory called worlds Webots is currently open and runs an arbitrary simulation Pause the current simulation by clicking on the Pause button of the 3D view The simulation is paused if the virtual time counter on the 3D view toolbar is hands on stable Create a new world by selecting the File gt New World menu item hands on A new world is now open For now the 3D window displays a black screen This is normal because the scene tree contains only the following fundamental nodes WorldInfo contain ing misc global parameters Viewpoint defining the main camera parameters and Back ground defining the background color As no light and no 3D object are defined the entire scene is empty and unlit and so black The first step is about to modify the background color Modify the background color by setting up the skyColor field of the Back ground node Choose a blue color e g red 0 4 green 0 7 and blue 1 0 using the color picker at the bottom of the scene tree The background of the 3D view should be modified accordingly hands on Now we would like to add some light to the scene 196 CHAPTER 7 TUTORIALS Select the last node of the scene tree view Background Click on the Add button at the top of the scene tree view In the open dialog box and choose New node gt DirectionalLight The new node has been added but hands on as there is no 3D object in the scene the re
138. ed Robotics Systems YEAR 2004 VOLUME 1 NUMBER 1 PAGES 39 42 URL http www ars Jjournal com International Journal of Advanced Robotic Systems Volume 1 39 42 pdf 58 CHAPTER 2 GETTING STARTED WITH WEBOTS Chapter 3 Sample Webots Applications This chapter gives an overview of sample worlds provided with the Webots package The exam ples world can be tried easily the wht files are located in various worlds directories of the WEBOTS_MODULES_PATH projects directory and can be directly opened from Webots us ing the Open Sample World item in File menu The controller code is located in the corresponding controllers directory This chapter provides each example a with short abstract only More detailed explanations can be found in the source code 3 1 Samples This section provides a list of interesting worlds that broadly illustrate Webots capabilities Sev eral of these examples have stemmed from research or teaching projects You will find the cor responding wbt files in the WEBOTS_MODULES_PATH projects samples demos worlds directory and their controller source code in the WEBOTS_MODULES_PATH projects samples demos controllers directory For each demo the world file and its corre sponding controller have the same name 59 60 CHAPTER 3 SAMPLE WEBOTS APPLICATIONS Figure 3 1 blimp_lis wbt 3 1 1 blimp_lis wbt Keywords Flying robot physics plugin keyboard joystick
139. ee e g read or change the position of robots the color of objects or switch on or off the light sources and do many other useful things One important thing to keep in mind is that the Supervisor functions correspond to function alities that are usually not available on real robots they rather correspond to a human intervention on the experimental setup Hence the Robot vs Supervisor distinction is intentional and aims at reminding the user that Supervisor code may not be easily transposed to real robots Now let s examine a few examples of Supervisor code 6 2 2 Tracking the Position of Robots The Supervisor is frequently used to record robots trajectories Of course a robot can find its position using a GPS but when it is necessary to keep track of several robots simultaneously and in a centralized way it is much simpler to use a Supervisor The following Supervisor code shows how to keep track of a single robot but this can easily be transposed to an arbitrary number of robots This example code finds a WoNodeRef that corresponds to the robot node and then a WoF ieldRef that corresponds to the robot s trans lation field At each iteration it reads and prints the field s values finclude lt webots robot h gt include lt webots supervisor h gt finclude lt stdio h gt int main wb_robot_init OCADMN PWN do this once only 6 2 SUPERVISOR PROGRAMMING 169 9 WoNodeRef robot
140. em shows or hides the The Scene Tree menu item opens the The Scene Tree menu item opens the Scene Tree window in which you can edit the virtual world Alternatively it is also possible to double click on some of the objects in the main window this automatically opens the Scene Tree with the corresponding object selected The Text Editor menu item opens the Webots text editor This editor can be used for editing and compiling controller source code The Console menu item opens the Webots Console which is a read only console that is used to display Webots error messages and controller outputs The Restore Layout menu item restores the factory layout of the panes of the main window The Clear Console menu item clears the console The Edit Physics Plugin menu item opens the source code of the physics plugin in the text editor The License Manager item opens the Webots License Manager window that allows you to see which license modules are in use and optionally to transfer some license modules to your local computer for off line use Please note that the transfer of license modules may be limited by your local license administrator It may not be possible to transfer some modules to your local computer or only for a limited duration depending on the configuration defined by your local license administrator Please ask your local license administrator in case of problem The Preferences item pops up a window described in this section 2 3 8 Wiz
141. er TouchSensor line following Rover Java In this example you can see the Mindstorms Rover robot from LEGO following a black line drawn on the ground In the middle of this line there is an obstacle which the robot navigates around after detecting a collision with it The robot will then recover its path As this robot is a Mindstorms robot its world file and its controller are in the mindstorms directory This example is written both in Java and C as a reference for translating Webots code from one language to another The source code for this controller is in the Rover directory 120 CHAPTER 3 SAMPLE WEBOTS APPLICATIONS Figure 3 60 scout2 wbt 3 5 28 scout2 wbt Keywords DifferentialWheels DistanceSensor Braitenberg Scout 2 In this example a Scout 2 robot moves inside an arena while avoiding the walls Its world file is in the others worlds directory Like many other examples this one uses the braitenberg con troller The source code for this controller is in the WEBOTS_MODULES_PATH projects default controllers braitenberg directory 3 5 REAL ROBOTS 121 Figure 3 61 shrimp wbt 3 5 29 shrimp wbt Keywords Robot node custom ODE plugin keyboard passive joint uneven ground sponginess Shrimp LinearMotor This example contains a model of the Shrimp robot which is a mobile platform for rough terrain from Bluebotics It has 6 wheels and a passive structure which allows it to adapt to the terrain profile and c
142. er evalu ation When the robot controller finishes the evaluation it writes the fitness result into another text file and then it calls the wo_supervisor_simulation_quit function to terminate Webots Then the control flow returns to the optimization program that can read the resulting fitness associate it with the current genotype and proceed with the next genotype Here is a possible pseudo code implementation for the robot evaluation controller 176 OANNDNFWN FR 15 16 17 18 19 20 21 Za 23 24 25 26 CHAPTER 6 PROGRAMMING FUNDAMENTALS include lt webots robot h gt include lt webots supervisor h gt define TIME_STEP 10 double genotype GENOME_SIZE int main wb_robot_init genotype_read genotype txt genotype run evaluation for double time 1000 0 read_sensors genotype Lor actuate_motors time wb_robot_step T1 double fitness compute_fitness fitness_save fitness wb_supervisor_sim 0 0 time lt 30 0 time TIME STEP ME STEP ulation_quit wb_robot_step TI ME LSI EP return 0 30 seconds genotype fitness EXE You will find complete examples of simulations using optimization techniques in Webots distri bution look for the worlds called advanced_particle_swarm_optimization wbt and advanced_genetic_algorithm wbt located in the WEBOTS_MODULES_PATH
143. er of DOF when modeling could be important to get an efficient simulation For example when modeling a caster wheel a realistic approach implies to model 2 DOF But if this degree of precision is useless for the simulation a more efficient approach can be found For example to model the caster wheel as a Sphere having a null friction coefficient with the ground The second step is to determine which solid node is the robot node the root node This choice is arbitrary but a solution is often much easier to implement For example in the case of an humanoid robot the robot node would be typically the robot chest because the robot symmetry facilitates the computation of the joint parameters In our case the body box is obviously the better choice The figure 7 15 depicts the solid nodes hierarchy of the robot At the end of the scene tree add a Robot node having four HingeJoints having a Solid child Please refer to figure 7 15 hands on Add a Shape node containing a Box geometry to the Robot node Set the color of the Shape to red Use the Shape to define also the boundingObject field of the Robot node The dimension of the box is 0 1 0 05 0 2 Add a Physics node to the Robot The figure 7 16 represents all the nodes defining hands on the robot So far only the direct children nodes of the root Robot node are implemented 226 children HingeJoint IN Other wheels Solid WHEEL1 CHAPTER 7 TUT
144. erID teams swapped 0 MAX 162 163 164 static const char get_team_name int team_colo 165 return team_names control_data teams team_co color 1 0 54 0 08 radius 0 0325 mass 0 055 gt centerOfMass linearDamping 0 17 E angularDamping 0 33 contactMaterial default gt Y Supervisor gt DEF GOAL_KEEPER_0 Nao_H21_V40 gt DEF PLAYER_1_0 Nao_H21_V40 DEF PLAYER 2 0 Nao H21 v40 169 static Robot robot_new WbNodeRef node 179 Robot robot malloc sizeof Robot 171 robot gt translation wb_supervisor_node get 172 robot gt rotation wb supervisor node get fie 173 robot gt waist_band_color wb supervisor_node 174 robot gt position NULL translation Vector3 O 176 find r 177 WbFieldRef controllerField wb_supervisor_n x 1 46228 m 178 const char controller wb supervisor field 179 if strstr controller nao 180 robot gt model NAO y 0 0323921 i m 181 else E 182 robot gt model DARWIN z 0 110715 m 183 IRA return rohot Console a INFO nao_team_1 Starting home projects contests robotstadium controllers nao_team_1 nao_team_1 INFO nao team 1 Starting home projects contests robotstadium controllers nao_team_1 nao_team_1 INFO nao team 1 Starting home projects contests robotstadium controllers nao_team_1 nao_team 1 INFO nao_team_1 Starting home projects contests robotstadium controllers nao_team_1 nao
145. erform these exer cises An example of this is located there see the figure 8 12 WEBOTS_MODULES_PATH projects robots thymio worlds thymio2_pen wbt https aseba wikidot com en thymiodrawing bodySlot 232 CHAPTER 8 ROBOTS Robot View Thymio II Motor PositionSensor TouchSensor DistanceSensor Accelerometer Motion Editor Figure 8 11 Thymio I robot window Untitled modified LO Keywords var if elseif else onevent while for sub Y var parti timer period 0 100 call leds top 0 0 32 Users fabien develop webots master projects robots thymio worlds thymio2_pen wbt onevent button forward td p z parti 1 E O Simulation View motor left target 200 motor right target 200 O amp 8 00 SAO Ib p D gt WM 0 01 02 010 0 42x gt call leds top 0 32 0 gt e Background 1 onevent button backward gt DirectionalLight partied gt DirectionalLight call leds top 32 0 0 RectangleArena motor left target 0 Y Thymio2 motor right target 0 translation 0 297 s onevent timer0 rotation 0 021167 if parti 1 then controller thymio motor left target motor left target 1 controllerArgs pc motor right target motor right target l end a a a a a a a a a gt thymio2_aseba_server Thymio II Aseba server thymio2_aseba_server Connect Aseba Studio or VPL for Thymio II to this controller through TCP IP thym
146. ery quickly when these nodes are used adequately A good graphics quality does not only enhance the user s experience it is also essential for simu lations where robots perceive their environment camera image processing line following etc The result at the end of this tutorial is shown in figure 7 8 7 4 1 New simulation From the results of the previous tutorial create a new simulation called appearance wbt by using the File gt Save World As menu hands on 7 4 2 Lights The lighting of a world is determined by light nodes There are three types of light nodes the DirectionalLight the PointLight and the SpotLight A Direc tionalLight simulates a light which is infinitely far ex the sun a PointLight simulates light emitted from a single point ex a light bulb and a Spot theory Light simulates a conical light ex a flashlight Each type of light node can cast shadows You can find their complete documentation in the Reference Manual Lights are costly in term of performance Minimizing the number of lights increases the rendering speed A maximum of 8 lights is allowed if the shaders are disabled in the Webots preferences A PointLight is more efficient than a note SpotLight but less than a DirectionalLight Note finally that casting shadows can reduce the simulation speed drastically Your simulation is currently lighted by a PointLight node at the top of the scene We want to repl
147. estarting Webots On Windows use the Task Manager the Task Manager can be started by pressing Ctrl Alt Delete In the Task Manager select the Processes tab then select each hal exe and naoqi bin exe line and push the End Process button for each one On Linux you can use the killall or the pki11 commands e g killall hal naoqi bin 8 3 USING THE THYMIO II ROBOT 249 Figure 8 8 Thymio II model in Webots 8 3 Using the Thymio II robot Thymio II is an affordable educational robot It provides three main features a large number of sensors and actuators an educative interactivity based on light and touch a programming environment featuring graphical and text programming More information about the Thymio II is available from its official website Webots contains an accurate model of the Thymio II robot see the figure 8 8 Almost all the Thymio II devices have been modeled and calibrated Moreover Aseba studio and VPL for Thymio II can be connected on the simulated model allowing you to program the simulated robot using Aseba Many Aseba examples are working directly with the simulated robot Finally several objects related to the Thymio II are available including a pen which can draw on any 3D object 8 3 1 Thymio II model The table 8 5 shows which devices are supported by the model and their names using the Webots terminology nttps aseba wikidot com en thymio 250 CHAPTER 8 ROBOTS
148. et_sf_vec3f is used to read the latest values of the specified field Note that unlike sensor or actuator functions the wb_su pervisor_field_x functions are executed immediately their execution is not postponed to the next wo_robot_step call 6 2 3 Setting the Position of Robots Now let s examine a more sophisticated Supervisor example In this example we seek to optimize the locomotion of a robot it should walk as far as possible Suppose that the robot s locomotion depends on two parameters a and b hence we have a two dimensional search space In the code the evaluation of the a and b parameters is carried out in the the while loop The actuateMotors function here is assumed to call wo_motor_set_postion for each motor involved in the locomotion After each evaluation the distance travelled by the robot is 170 CHAPTER 6 PROGRAMMING FUNDAMENTALS measured and logged Then the robot is moved translation back to its initial position 0 0 5 0 for the next evaluation To move the robot we need the wo_supervisor_x functions and hence the base node of this robot in the Scene Tree must be a Supervisor and not a Robot include lt webots robot h gt include lt webots supervisor h gt include lt stdio h gt include lt math h gt define TIME STEP 32 int main wb_robot_init Re PSP OVO0_ DMaMUR DN a get handle to robot s translation field 12 WbNodeRef robot_node wb_supervisor_n
149. eter_get_values WbDeviceTag tag 3 const double x wb_gyro_get_values WbDeviceTag tag Each function returns a pointer to three double values The pointer is the address of an array allocated by the function internally These arrays should never be explicitly deleted by the con troller code They will be automatically deleted when necessary The array contains exactly three double values Hence accessing the array beyond index 2 is illegal and may crash the controller Finally note that the array elements should not be modified for this reason the pointer is declared as const Here are correct examples of code using these functions 158 CHAPTER 6 PROGRAMMING FUNDAMENTALS l const double pos wb_gps_get_values gps 3 OK to read the values they should never be deleted by the controller code 4 printf MY_ROBOT is at position g_ g_ g n pos 0 pos 1 pos 2 a 6 OK to copy the values 7 double x Y zZ 8 x pos 0 9 ly pos 1 10 z pos 2 11 12 OK another way to copy the values 13 double a 3 pos 0 pos 1 pos 2 14 15 OK yet another way to copy these values 16 double b 3 17 memcpy b pos sizeof b explicitly And here are incorrect examples l const double xpos wb_gps_get_values gps 2 3 pos 0 3 5 ERROR assignment of read only location 4 double a pos 3 ERROR ind
150. evationGrid node but it can only be used to model a flat terrain while the ElevationGrid can be used to model an uneven terrain 222 CHAPTER 7 TUTORIALS 7 6 6 Contacts When two solids collide contacts are created at the collision points Contact Properties nodes can be used to specify the desired behavior of the contacts q e g the friction between the two solids N F Each solid belongs to a material category referenced by their contact Material field default by default The WorldInfo node has a con tactProperties field that stores a list of ContactProperties nodes These nodes allow to define the contact properties between two categories of Solids theory We want now to modify the friction model between the dumbbell and the other solids of the environment Set the contactMaterial field of the dumbbell to dumbbell In the WorldInfo node add a ContactProperties node between the default and dumbbell categories Try to set the coulombFriction field to 0 and hands on remark that the dumbbell slides instead of rotating on the floor because no more friction is applied 7 6 7 basicTimeStep ERP and CFM The most critical parameters for a physics simulation are stored in the basicTimeStep ERP and CEM fields of the WorldInfo node The basicTimeStep field determines the duration in ms of a physics step The bigger this value is the quicker the simulation is the less precise th
151. ew students use all the licenses permanently 32 CHAPTER 1 INSTALLING WEBOTS 1 6 4 Using Webots without Internet connection It is possible to use Webots without any Internet connection for a limited amount of time Users who anticipate they will be away from the Internet can download a license locally on their ma chine for a specified lease duration During this period of time the license is considered to be in use and is not available to other users The maximum lease duration can be defined by the administrator of the licenses in the Edit module pack administration web page It can be set to None to prevent any off line use of Webots Otherwise the maximum lease value can be chosen between 1 hour and 7 days In order to download a license locally for off line use a user should go to the Tools menu of Webots and open the License Manager item A new window should pop up to display the available licenses The user can then choose which licenses to download on his local computer as well as the duration of the lease for these licenses Warning this operation cannot be undone Once transferred locally the licenses are not available to other computers for the duration of the lease period 1 7 Translating Webots to your own language Webots is translated into French German Spanish Chinese and Japanese and partially into Italian However since Webots is always evolving including new text or changing existing wording these
152. ex out of range 5 delete pos ERROR illegal free 6 free pos ERROR illegal free 6 1 3 Using Actuators The example below shows how to make a rotational motor oscillate with a 2 Hz sine signal Just like sensors each Webots actuator must be identified by a Wh DeviceTag returned by the wob_robot_get_device function However unlike sensors actuators don t need to be expressly enabled they actually don t have wb_x_enable functions To control a motion it is generally useful to decompose that motion in discrete steps that cor respond to the control step As before an infinite loop is used here at each iteration a new target position is computed according to a sine equation The wb_mo function stores a new position request for the corresponding rotation tor_set_position al motor Note that wb_ motor_set position stores the new position but it does not immediately actuate the motor The effective actuation starts on the next line in the call to wo_robot_step The wb_robot_step function sends the actuation command to the RotationalMotor but 6 1 CONTROLLER PROGRAMMING 159 it does not wait for the RotationalMotor to complete the motion i e reach the specified target position it just simulates the motor s motion for the specified number of milliseconds 1 finclude lt webots robot h gt 2 include lt webots motor h gt 3 include l
153. f the Python API For advanced users who want to modify the Python API the SWIG script controller i and the Makefile are located in the resources languages python directory while the generated library is located in the Lib 4 7 Using MATLAB 4 7 1 Introduction to MATLAB MATLAB is a numerical computing environment and an interpreted programming language MATLAB allows easy matrix manipulation plotting of functions and data implementation of algorithms and creation of user interfaces You can get more information on the official MathWorks web site MATLAB is widely used in robotics in particular for its Image Pro cessing Neural Networks and Genetics Algorithms toolboxes Webots allows to directly use MATLAB scripts as robot controller programs for your simulations Using the MATLAB interface it becomes easy to visualize controller or supervisor data for example processed images sensor readings the performance of an optimization algorithm etc while the simulation is running In addition it becomes possible to reuse your existing MATLAB code directly in Webots 4 7 2 How to run the Examples If MATLAB is already installed you can directly launch one of the MATLAB examples For doing that start Webots and open the world file WEBOTS_MODULES_PATH projects languages matlab worlds e puck_matlab wbt or the world file WEBOTS_MODULES_ PATH projects robots aldebaran worlds nao2_matlab wbt in your Webots installation directo
154. f the robots The source code for this client is in the file ipr_ serial client ipr_factory c 106 CHAPTER 3 SAMPLE WEBOTS APPLICATIONS Figure 3 46 ipr models wbt 3 5 14 ipr_models wbt Keywords Robot node robotic arm TCP IP IPR IndexedFaceSet RotationalMotor active Joint In this example you can see all the different types of IPR model provided by Webots HD6M180 HD6Ms180 HD6M90 and HD6Ms90 This world is intended to be the example from which you can copy the models of IPR robots into your own worlds All the IPR robots use the same controller whose source code is in the ipr_serial directory 3 5 REAL ROBOTS 107 Figure 3 47 khepera wbt 3 5 15 khepera wbt Keywords DifferentialWheels DistanceSensor Braitenberg texture Khepera In this example you can see a Khepera robot from K Team moving inside an arena while avoiding the walls Like many other examples this one uses the braitenberg controller The source code for this controller is located in the WEBOTS_MODULES_PATH projects default controllers braitenberg directory 108 CHAPTER 3 SAMPLE WEBOTS APPLICATIONS Figure 3 48 khepera2 wbt 3 5 16 khepera2 wbt Keywords DifferentialWheels DistanceSensor Braitenberg texture Khepera II In this example you can see a Khepera II robot from K Team moving inside an arena while avoiding the walls Like many other examples this one uses the braitenberg controller The source code for this control
155. fined values Enabling a sensor is achieved using the corresponding wb_x_enable function where the star stands for the sensor type Every wb_ _enable function allows to specify an update delay in milliseconds The update delay specifies the desired interval between two updates of the sensor s data In the usual case the update delay is chosen to be similar to the control step TIME_STEP and hence the sensor will be updated at every wb_robot step If for example the update delay is chosen to be twice the control step then the sensor data will be updated every two wb_ robot_step this can be used to simulate a slow device Note that a larger update delay can also speed up the simulation especially for CPU intensive devices like the Camera On the contrary it would be pointless to choose an update delay smaller than the control step because it will not be possible for the controller to process the device s data at a higher frequency than that imposed by the control step It is possible to disable a device at any time using the corresponding wb_ _disable function This may increase the simulation speed The sensor value is updated during the call to wo_robot_step The call to wo dis tance_sensor_get_value retrieves the latest value Note that some device return vector values instead of scalar values for example these functions l const double wb_gps_get_values WbDeviceTag tag 2 const double wb_accelerom
156. frame rendering mode only the segments of the ren derable primitives are rendered This mode can be useful to debug your meshes If the wireframe rendering mode and the View gt Optional Rendering gt Show All Bounding Objects toggle button are both activated then only bounding objects are drawn not the renderable primitives This can be used to debug a problem with the collision detection Finally the Optional Rendering submenu allows to display or to hide supplementary informa tion These rendering are displayed only in the main rendering and hide in the robot camera They are used to understand better the behavior of the simulation The Show Coordinate System allows to display or to hide the global coordinate system at the bottom right corner of the 3D window as red green and blue arrows representing the x y and z axes respectively The Show All Bounding Objects allows to display or to hide all the bounding objects defined in the bounding Object fields of every Solid node Bounding objects are represented by white lines These lines turn rose when a collision occurs and blue when the solid is idle i e it comes to rest and it doesn t interact with any other active solid The Show Contact Points allows to display or to hide the contact points generated by the colli sion detection engine Contact points that do not generate a corresponding contact force are not shown A contact force is generated only for objects simulated w
157. g a compo sition of primitives in a Group or a Transform when a single primitive would do the trick Chapter 10 Known Bugs This chapter lists the bugs known by Cyberbotics They are not planned to be resolved on the short term but possible workarounds are explained 10 1 General bugs 10 1 1 Intel GMA graphics cards Webots should run on any fairly recent computer equipped with a nVidia or ATI graphics card and up to date graphics drivers Webots is not guaranteed to work with Intel GMA graphics cards it may crash or exhibit display bugs Upgrading to the latest versions of the Intel graphics driver may help resolve such problems without any guarantee Graphics drivers from Intel may be obtained from the Intel download center web site Linux graphics drivers from Intel may be obtained from the Intel Linux Graphics web site 10 1 2 Virtualization Because it highly relies on OpenGL Webots may not work properly in virtualized environments such as VMWare or VirtualBox which often lack a good OpenGL support Hence Webots may exhibit some display bugs run very slowly or crash in such environments 10 1 3 Collision detection Although collision detection works well generally well Cy linder Cylinder Cylinder Capsule IndexedFaceSet IndexedFaceSet and IndexedFaceSet Cylinder Inttp downloadcenter intel com http intellinuxgraphics org 275 276 CHAPTER 10 KNOWN BUGS collision detection ma
158. g its m file from MATLAB prompt Note that this will restart the controller only not the whole simulation so the current robot and motor positions will be preserved If you want to restart the whole simulation you need to use the Revert button as usual 6 6 Controller Plugin The controller functionality can be extended with user implemented plugins The purpose of a controller plugin is to facilitate the programming of robot specific robot windows and remote control wrappers Programming controller plugins rather than programming directly in the controller is more con venient because it increases considerably the modularity and the scalability of the code For example a robot window can be used for several robots 6 6 1 Fundamentals Whatever its language a controller executable is linked with the Webots controller library lib Controller at startup A controller plugin is a shared library loaded dynamically at runtime by libController after a specific event depending on its type The figure 6 3 shows an overview of the controller plugin system In this figure the dashed arrows shows how the shared libraries are loaded and the large dash lines represents an Inter Process Communication IPC The IPC between libController and Webots is a pipe On Win dows this is a named pipe and otherwise a local domain socket The IPC between libRemote Control and the real robot is defined by the user TCP IP Serial etc The system ha
159. gt define TIME _STEP 32 int main wb_robot_init NV 0 JD lona 164 CHAPTER 6 PROGRAMMING FUNDAMENTALS 10 WbDeviceTag ds wb_robot_get_device my_distance_sensor 11 wb_distance_sensor_enable ds TIME_STEP 12 13 while wb_robot_step TIME_STEP 1 14 double dist wbh_distance_sensor_get_value 15 printf sensor value is sfin dist 16 17 18 Webots triggered termination detected 19 20 saveExperimentData 21 22 wb_robot_cleanup 25 24 return 0 25 In some cases it is up to the controller to make the decision of terminating the simulation For example in the case of search and optimization algorithms the search may terminate when a solution is found or after a fixed number of iterations or generations In this case the controller should just save the experiment results and quit by returning from the main function or by calling the exit function This will terminate the controller process and freeze the simulation at the current simulation step The physics simulation and every robot involved in the simulation will stop freeze the whole simulation if finished saveExperimentData l exit 0 NBhuUn If only one robot controller needs to terminate but the simulation should continue with the other robots then the terminating robot should call wb_robot_cleanup right before quitting terminate on
160. has to be sent to the real robot The complete definition of the remote control API and of the WorInterface structure is contained in WEBOTS_HOME include controller c webots remote_control h For example if you want to be able to use the distance sensor of the real robot you have to wrap the wor_set_refresh_rate function to set the internal state of the remote control library to read this distance sensor only when required and to call wor_distance_sensor_set_ value into the remote control library when the distance sensor is refreshed typically into the wor_robot_step function A complete sample communicating with the e puck robot using bluetooth can be found in this directory WEBOTS_MODULES_PATH projects robots e puck plugins remote_controls e puck_bluetooth 6 7 Webots Plugin Webots functionality can be extended with user implemented plugins 190 CHAPTER 6 PROGRAMMING FUNDAMENTALS 6 7 1 Physics Plugin A physics plugin offers the possibility to add custom ODE instructions to the default physics behavior of Webots For instance it is possible to add or measure forces By adding forces it is possible to simulate new types of environments or devices For example a wind can be simulated as a constant unidirectional force applied to each object in the world and proportional to the size of the object The reactor of an airplane can be simulated by adding a force of varying intensity etc Webots distribution c
161. hat after the same number of steps two simulations will have exactly the same internal state Hence if both simulation are saved using the Save as button the resulting files will be identical This is true independently of the simulation mode used to execute the simulation Step Real Time Run or Fast This is also true whether or not sensor noise is used see below 9 3 MODELING 271 9 3 3 How to remove the noise from the simulation There are two sources of noise in Webots the sensor actuator noise and the physics engine noise The amount of sensor actuator noise can be changed or removed by the user see below The physics engine s noise cannot be changed because it is necessary for the realism of the simulation To completely remove the sensor actuator noise the following field values must be reset 1 In the lookupTables the third column of each 1lookupTable in the wbt and proto files must be reset to 0 2 In the GPS nodes the resolution field must be reset to O 3 In the Camera nodes the colorNoise and the rangeNoise fields must be reset to 0 4 Inthe DifferentialWheels nodes the value of s1ipNoise must be reset to 0 and the value of encoderNoise must be reset to 1 9 3 4 How can I create a passive joint First of all any joint passive or active must be created by adding a Joint derived node de pending on the constraint type requested in the Scene Tree A Joint is passive if its device is null or at le
162. he chapter 6 128 CHAPTER 4 LANGUAGE SETUP 4 4 2 C Compiler Installation Please refer to the instructions for the C Compiler installation here 4 4 3 Source Code of the C API The source code of the C API is available in the Webots release You may be interested in looking through the directory containing the header files include controllers cpp in order to get the precise definition of every classes and functions although the reference guide offers a clean description of the public functions This directory is automatically included when the C controller is compiled For users who want to use a third party development environment it is useful to know that the shared library CppController dll libCppController so orlibCppController dy lib is located in the 1ib subdirectory of your Webots directory This directory is automat ically included when the C controller is linked For advanced users who want to modify the C API the C sources and the Makefile are located in the resources languages cpp directory 4 5 Using Java 4 5 1 Introduction The Java API has been generated from the C API by using SWIG That implies that their class hierarchy their class names and their function names are almost identical The Java API is currently composed of a set of about 25 classes having about 200 public functions located in the package called com cyberbotics webots controller The classes are either representations of a no
163. he Console window 3 2 WEBOTS DEVICES 79 Figure 3 20 gps wbt 3 2 9 gps wbt Keywords GPS Supervisor DifferentialWheels keyboard This example shows two different techniques for finding out the current position of a robot The first technique consists in using an on board GPS device The second method uses a Supervi sor controller that reads and transmits the position info to the robot Note thata Supervisor can read or change the position of any object in the simulation at any time This example im plements both techniques and you can choose either one or the other with the keyboard The G key prints the robot s GPS device position The S key prints the position read by the Supervisor 80 CHAPTER 3 SAMPLE WEBOTS APPLICATIONS Figure 3 21 led wbt 3 2 10 led wbt Keywords LED DifferentialWheels In this example a robot moves while randomly changing the color of three LE 1ts body The color choice is printed in the Console Ds on the top of 3 2 WEBOTS DEVICES 81 Figure 3 22 light_sensor wbt 3 2 11 light sensor wbt Keywords LightSensor PointLight lamp light following In this example the robot uses two Light Sensors to follow a light source The light source can be moved with the mouse the robot will follow it 82 CHAPTER 3 SAMPLE WEBOTS APPLICATIONS We e Figure 3 23 pen wbt 3 2 12 pen wbt Keywords Pen keyboard In this example a robot uses a Pen device
164. he for mer is a CMake file that tells catkin how to build the ROS package the latter is a description of the package where you can specify the package dependen cies the version number the author name the maintainer name etc If you want to use the ROS command line tools roscd rosls rospack to navigate and get information about the created pack age then you need to call catkin_make at the root of the catkin workspace and source the file devel setup bash cd my_ros controllers joystick catkin_ws S catkin_make S source devel setup bash Now the output of the command rospack find webots_joystick should be note my_ros controllers joystick catkin_ws src webots_joystick The information on package first level dependencies which are displayed after the rospack dependsl webots_joystick command should read as joy roscpp Copy the original cpp controller file into your package resource directory cd my_ros controllers joystick catkin_ws src webots_joystick src cp SWEBOTS_MODULES_PATH projects languages ros hands on controllers joystick catkin_ws src webots_joystick src webots_joystick_node cpp 232 CHAPTER 7 TUTORIALS In the file webots_ joystick CMakeLists txt uncomment the line fadd_executable webots_joystick_node src webots_joystick_node cpp and append the following lines set WEBOTS_HOME SENV WEBOTS_HOME add_definitions IS WEBOTS_HOME include contr
165. he simulation at real time until it is interrupted by Pause or Step In run mode the 3D display of the scene is refreshed every n basic time steps where n is defined in the displayRefresh field of the worldInfo node 44 CHAPTER 2 GETTING STARTED WITH WEBOTS The Run menu item and button is like Real time except that it runs as fast as possible Webots PRO only The Fast menu item and button is like Run except that no graphical rendering is per formed Webots PRO only As the graphical rendering is disabled black screen this allows for a faster simulation and therefore this is well suited for cpu intensive simulations genetic algorithms vision learning etc 2 3 5 Build Menu The Build menu provides the functionality to compile or cross compile controller code The build menu is described in more details here 2 3 6 Robot Menu The Robot menu provides actions specific to Robot nodes Some actions of this menu are active only when a robot is selected in the 3D window or when there is only one robot in the simulation The Edit Controller menu item opens the source file of the controller of the selected robot The Camera Devices submenu contains the list of all the camera devices of the selected robot and lets the user show or hide single camera overlay images by checking or unchecking the corresponding item Camera overlays differ from the display overlays because of their magenta border Note that if the
166. hey will be written directly with no syntax change It s a good place for variables that don t contain any path e environment variables for Windows Variables defined in this section will only be added to the environment if the controller is run on the Windows platform If you want to declare paths in this section the value should be written between double quotes symbols e environment variables for Mac OS X Variables defined here will only be added on Mac OS X and ignored on other platforms e environment variables for Linux Variables defined here will be added on all Linux platforms but not on Mac or Windows e environment variables for Linux 32 These variables will be added only if the Linux platform is 32 bit e environment variables for Linux 64 These variables will be added only if the Linux platform is 64 bit Here is an example of a typical runtime ini file 1 typical runtime ini 2 3 environment variables with relative paths 4 WEBOTS_LIBRARY_PATH lib WEBOTS_LIBRARY_PATH library 3 6 environment variables 7 ROS_MASTER_URI http localhost 11311 8 9 environment variables for Windows 10 NAOQI_LIBRARY_FOLDER bin C Users My Documents Naoqi bin 11 12 environment variables for Mac OS X 13 NAOQI_LIBRARY_FOLDER lib 14 15 environment variables for Linux 16 NAOQI_LIBRARY_FOLDER lib 6 2 SUPERVISOR PROGRAMMING 16
167. horegraphe toggle the Wake up button which is a little sun in the rop right of the window Nao is currently in the Stand Zero pose you can change its starting pose using the posture library in Choregraphe Then double click on any of the Nao parts in Choregraphe a small window with control sliders appears Now move any of the sliders the motor movement in Choregraphe should be reflected in the Webots simulation If you open the Video monitor in Choregraphe you should see the picture of the Nao camera simulated by Webots 8 2 3 Nao models You can switch between the Nao model thanks to the following Nao PROTO fields e version corresponds to the real Nao version The supported versions are 3 3 4 0 and 5 0 The main difference between these models is the different calibration of the physics The field of view of the cameras is slightly different too Please refer directly to the Nao proto file to see the complete difference Note that each version having a different weight repartition in their body the best contact properties in the simulated world aren t always the same They are currently optimized for the version 5 0 of Nao in the default Nao worlds and may not perform as well with previous versions of Nao 8 2 4 Using motion boxes Now we can test some of the motion boxes of Choregraphe A simple example is a sit down gt stand up motion In Choregraphe select the Sit Down and Stand Up boxes from Box
168. ialized at all or because it is corrupted by a programming error in the controller code Here is such an example include lt webots robot h gt include lt webots camera h gt 266 CHAPTER 9 WEBOTS FAQ include lt webots distance_sensor h gt define TIME _STEP 32 int main wb_robot_init WbDeviceTag distance_sensor camera wb_robot_get_device camera wb_camera_enable camera TIME_STEP wb_distance_sensor_enable distance_sensor TIME_STEP WRONG 9 2 6 Is it possible to apply a user specified force to a robot Yes You need to use a physics plugin to apply user specified forces or torques Note that Webots PRO is required to create a physics plugin Then you can add the physics plugin with the menu item Wizards gt New Physics Plugin After having added the plugin you must compile it using Webots editor Then you must associate the plugin with your simulation world This can be done by editing the WorldInfo physics field in the Scene Tree Then you must modify the plugin code such as to add the force Here is an example include lt ode ode h gt include lt plugins physics h gt dBodyID body NULL void webots_physics_init find the body on which you want to apply a force body dWebotsGetBodyFromDEF MY_ROBOT void webots_physics_step dVector3 f f 0 f 1 f 2 at every time step add a force to the body dBodyAddForce body f 0
169. icetTag is an abstract reference or handle used to identify a simulated device in Webots Any WoDeviceTag must be obtained from the wo_robot_get_device function Then it is used to specify a device in various Webots function calls Webots issues this warning when the WoDeviceTag passed to a Webots function appears not to correspond to a known device This can happen mainly for three reasons 1 The WoDeviceTag is 0 and thus invalid because it was not found by wb_robot_get_ device Indeed the wo_robot_get_device function returns 0 if it cannot not find a device with the specified name in the robot Note that the name specified in the argument of the wo_robot get device function must correspond to the name field of the device not to the VRML DEF name 2 Your controller code is mixing up two types of WoDeviceTags for example because it uses the WoDeviceTag of a Camera in a wo_distance_sensor_x function Here is an example of what is wrong include lt webots robot h gt include lt webots camera h gt include lt webots distance_sensor h gt define TIME_STEP 32 int main wb_robot_init WoDeviceTag Camera wb_robot_get_device camera wb_camera_enable camera TIME_STEP double value wb_distance_sensor_get_value camera WRONG 3 The WoDeviceTag may also be invalid because it is used before initialization with wb_ robot_get_device or because it is not init
170. iew the simulation in wireframe mode by using the View gt Wireframe Ren dering menu item Then restore the plain rendering mode View gt Plain Ren hands on dering 7 4 6 Conclusion In this tutorial you have learnt how to set up a good looking environment using the Appearance node and the light nodes You can go further on this topic by reading the detailed description of these nodes in the Refer ence Manual The subsection 9 3 7 will give you a method to efficiently setup these nodes 7 5 Tutorial 4 More about Controllers 20 minutes Now we start to tackle the topics related to programming robot controllers We will design a simple controller that avoids the obstacles created in the previous tutorials This tutorial will introduce you to the basics of robot programming in Webots At the end of this chapter you should understand what is the link between the scene tree nodes and the controller API how the robot controller has to be initialized and cleaned up how to initialize the robot 7 5 TUTORIAL 4 MORE ABOUT CONTROLLERS 20 MINUTES 211 devices how to get the sensor values how to command the actuators and how to program a simple feedback loop This chapter only addresses the correct usage of Webots functions The study of robotics algo rithms is beyond the goals of this tutorial and so this won t be addressed here Some rudimentary programming knowledge is required to tackle this chapter any C tutorial should b
171. ifferent kind of nodes involved in the building of the robot models the way to translate and rotate a solid relatively to another the way that a rotational motor is actuated by the controller 7 8 TUTORIAL 7 USING ROS 229 7 8 Tutorial 7 Using ROS This tutorial explains how to implement a Webots controller as a ROS node This process is ex emplified by describing how we built the joystick controller located in WEBOTS_MODULES_ PATH projects languages ros controllers joystick We assume that you installed ROS groovy on your computer as explained in the online ROS installation tutorial As the ROS joy package is currently defined on Linux only you won t be able to compile this controller example t dd on other platforms 7 8 1 Creating a Webots project that contains a ROS package The joystick controller is a Webots controller written in C and implemented as a ROS node It subscribes to the joy joy topic of the joy_node see ROS joy package in order to listen to the joystick state The relevant line in webots_joystick_node cpp is ros Subscriber sub nh subscribe joy 10 Joy_callback which prompts ten times per second the callback function joycall_back to transform the joystick sensed values into a robot motion command We now describe the actions to setup the controller directory WEBOTS_MODULES_PATH projects languages ros controllers joystick both on ROS and Webots side as provided in your Webots distri
172. ile The Pioneer 3 DX motors are RotationalMotor nodes named according to figure 8 20 The wb_ set motor_position and wb_set_motor_velocity functions allow the user to manage the rotation of the wheels The sonar sensors are numbered according to figure 8 17 The angle between two consecutive sensor directions is 20 degrees except for the four side sen sors so0 so7 so8 and so15 for which the angle is 40 degrees 260 CHAPTER 8 ROBOTS Chapter 9 Webots FAQ This chapter is a selection of frequently asked questions found on the Webots forum You may find additional information directly in the group Other useful sources of information about Webots include Webots Reference Manual and Cyberbotics Robot Curriculum 9 1 General FAQ 9 1 1 What are the differences between Webots PRO Webots EDU and other Webots modules Webots PRO provides a fully featured version of Webots intended for robotics research We bots EDU provides a special version of Webots well suited for education Webots modules are components tailored for specific uses of Webots they include different models of robots objects environments programming interfaces libraries etc Users can purchase only the modules they need separately The differences between Webots modules are explained here 9 1 2 How can I report a bug in Webots If you can still start Webots please report the bug by using Webots menu Help gt Bug report If Webots ca
173. interpretable file must also be named after the controller field of the Robot plus a possible extension For example if the controller field of the robot looks like this in the Scene Tree Robot controller my_controller then the executable interpretable file will be searched at the following paths my_project controllers my_controller my_controller exe Windows only my_project controllers my_controller my_controller Linux Mac only my_project controllers my_controller my_controller class my_project controllers my_controller my_controller py my_project controllers my_controller my_controller m If Webots does not find any file at the above specified paths then the error message in question 1s shown So this problem often happens when you e Have moved the project or source files to a location that does not correspond to the above description e Use an external build system e g Visual Studio that is not configured to generate the executable file at the right location http ode wiki org wiki index php title Manual 9 2 PROGRAMMING 265 e Have changed the Robot s controller field to a location where no executable interpretable file can be found e Have reverted the world after cleaning of the controller project 9 2 5 What does this mean Warning invalid WbDeviceTag in API func tion call A WbDev
174. io2_aseba_server Use the Thymio II robot window to access some special events tap clap etc thymio2_aseba_server Change the server port using the Thymio2 controllerArgs field thymio2_aseba_server Server started on port 33333 thymio2_aseba_server New client connected Figure 8 12 Simulation of a Thymio II having a pen 8 4 USING THE PIONEER 3 AT AND PIONEER 3 DX ROBOTS 233 0 running Keywords var i eleit ele onevent while for sub 1 Pause 1 var accTampon0 4 0 0 0 0 w Next r accTam 0 0 0 0 0 0 Users fabien develop webots master projects robots thymio worlds thymio2_ball wbt Simulation View 0 01 01 330 0 87 8 onevent acc 8800 SBO Ib p D gt WD 0 01 01 330 0 97x 9 accTampon0 accTamponfos0 acc 0 2 fici or Worldinfo re i acc l rom tre qui donne gt Viewpoint 5i ccTamponPos0 1 4 Background 1 cTampon0 0 accTampon0 1 gt DirectionalLight amponO 3 gt DirectionalLight 12 ccTamponPos1 acc 1 tici o gt CircleArena pr e de l acc l rom tre qui don Thymio2 gt Thymio2Ball 13 accTamponPosl accTamponPosl 1 4 14 sumaccl accTampon1 0 accTampon1 1 accTampon1 2 accTamponl 3 15 16 motor left target sumacc0 15 sumaccl 15 17 motor right target sumacc0 15 sumacc1 15 Compilation success yw Figure 8 13 Simulation of a Thymio II above a ball 8 3 4 Thymio II Ball Thes
175. ion you can find it directly at etc hosts on Mac OS X it is located at private etc hosts on Windows it is located at C Windows System32 drivers etc hosts On Windows and Mac OS X this a hidden path and you will need to search di rectly for this path The hosts file is usually protected and you will need administrator or root right to edit it note Custom Controller The standard controller has been developed in order to work on every robot and for general purpose Sometimes you may not be able to do what you want with this controller or it would be too complicated In this case you can build your own custom controller and ROS node It is possible to implement such a ROS node in C using the roscpp library However in this case you need to setup a build configuration to handle both the cat kin_make from ROS and the Makefile from Webots to have the resulting binary linked both against the Webots libController and the roscpp library An example of such an implementation is included in the Webots distribution see below This controller can also be implemented in Python by importing both ROS libraries roslib rospy and Webots libraries controller in a Webots robot or supervisor controller Using the Custom Controller A sample C ROS node running as a Webots controller is provided in the Webots distribution for Linux It is located in the Webots WEBOTS_MODULES_PATH projects languages ros custom folder and contains a
176. irecting Webots console output to 38 CHAPTER 2 GETTING STARTED WITH WEBOTS the calling terminal or process For example this can be used to redirect the controllers output to a file or to pipe it to a shell command stdout redirects the stdout stream of the controllers while stderr redirects the stderr stream Note that the stderr stream may also contain Webots error or warning messages The disable modules download option disables the download of new modules and therefore prevents the Webots Update Manager window from poping up The force modules download will instead force the automatic download of new modules if available without asking the user Both options are mutually exclusive The start streaming server option starts the Webots streaming server An option can be given to change the default parameters of the streaming server This option is a string containing a list of parameter keys and their values separated by semicolons The supported options are described in table 2 1 Key Value example Description port 1234 The port on which the streaming server is open Table 2 1 Streaming server options For example the following command will start Webots with the streaming server enabled on the TCP port 1234 webots start streaming server port 1234 2 3 The User Interface Webots GUI is composed of four principal windows the 3D window that displays and allows to interact with the
177. it is not possible to call the Supervisor methods from a DifferentialWheels controller and vice versa For example it won t be possible to call simulationRevert fromaDiffer entialWheels controller Generally the user defined controller class should have a run function that implements the main controller loop That loop should contains a call to the Robot s step method Then the only responsibility of the controller s main function is to create an instance of the user defined controller class call its run method and finally delete C only the instance see examples below Note that the controller should never create more than one instance of a derived class otherwise the results are undefined Note that unlike the C API the C Java Python APIs don t have and don t need functions like wb_robot_init and wb_robot_cleanup The necessary initialization and cleanup routines are automatically invoked from the constructor and destructor of the base class In C Java Python each Webots device is implemented as a separate class there is a Dis tanceSensor class a TouchSensor class a RotationalMotor class etc The various 6 4 C JAVA PY THON 179 devices instances can be obtained with dedicated methods of the Robot class like getDis tanceSensor getTouchSensor etc ThereisnoWbDeviceTag in C Java Python 6 4 3 C Example 1
178. ith physics Physics node required A step is required for taking this operation into account The Show Connector axes allows to display or to hide the connector axes The rotation align ments are depicted in black while the y and z axes respectively in green and blue The Show Joint axes allows to display or to hide the joint axes The joint axes are represented by black lines The Show Camera frustums allows to display or to hide the OpenGL culling frustum for every camera in the scene using a magenta wire frame The OpenGL culling frustum is a truncated 2 3 THE USER INTERFACE 43 pyramid corresponding to the field of view of a camera The back of the pyramid is not repre sented because the far plane is set to infinity More information about this concept is available in the OpenGL documentation The Show Distance Sensor rays allows to display or to hide the rays casted by the distance sensor devices These rays are drawn as red lines which become green beyond collision points Their length corresponds to the maximum range of the device The Show Light Sensor rays allows to display or to hide the rays casted by the light sensor devices These rays are drawn as yellow lines The Show Lights allows to display or to hide the lights including PointLights and SpotLights DirectionalLights aren t represented PointLights and SpotLights are represented by a colored circle surrounded by a flare The Show Pen Painting Rays
179. l find instructions there Mac OS X Instructions In order to compile C C controllers on the Mac you will need to install Apple Xcode Xcode is a suite of tools developed by Apple for developing software for Mac OS X Xcode is free and can be downloaded from the Apple App Store Webots will need principally the gcc GNU C Compiler and make commands of Xcode To install these commands start Xcode and go to Xcode menu Preferences Downloads Components and click Install for Command Line Tools Linux Instructions For compiling C controllers Webots will need the GNU C Compiler and GNU Make utility On Linux these tools are often pre installed otherwise you will need to install them separately gcc and make packages For C you will also need the GNU C Compiler g package Optionally you can also install the GNU Debugger gdb package 4 4 Using C 4 4 1 Introduction The C API is a wrapper of the C API described in the previous section The major part of the C functions has been wrapped in a function of a specific class It is currently composed of a set of about 25 classes having about 200 public functions The classes are either representations of a node of the scene tree such as Robot LED etc or either utility classes such as Motion ImageRef etc A complete description of these functions can be found in the reference guide while the instructions about the common way to program a C controller can be found in t
180. l robots e g swarm robotics or if your robot is a DifferentialWheels then it is advised to use two distinct types of controller one for the optimization algorithm and one for the robot s behavior The optimization algorithm should go in a Supervisor controller while the robots behavior can go in a regular non Supervisor controller Because these controllers will run in separate system processes they will not be able to access each other s variables Though they will have to communicate by some other means in order to specify the sets of parameters that need to be evaluated It is possible and recommended to use Webots Emitters and Receivers to exchange information between the Supervisor and the other controllers For example in a typical scenario the Supervisor will send evaluation 6 3 USING NUMERICAL OPTIMIZATION METHODS 173 parameters e g genotype to the robot controllers The robot controllers listen to their Re ceivers waiting for a new set of parameters Upon receipt a robot controller starts executing the behavior specified by the set of parameters In this scenario the Supervisor needs an Emitter and each individual robot needs a Receiver Depending on the algorithms needs the fitness could be evaluated either in the Supervisor or in the individual robot controllers In the case it is evaluated in the robot controller then the fitness result needs to be sent back to the Supervisor This bidirectional type of com
181. lass hierarchy their class names and their function names are almost identical The Python API is currently composed of a set of about 25 classes having about 200 public functions located in the module called controller The classes are either representations of a node of the scene tree such as Robot LED etc or either utility classes such as Motion ImageRef etc A complete description of these functions can be found in the reference guide while the instructions about the common way to program a Python controller can be found in chapter 6 4 6 2 Python Installation Version The Python API of Webots is built with Python 2 7 Python 2 7 or earlier versions are there fore recommended although more recent versions can work without guarantee Python 3 is not supported Mac OS X and Linux Instructions Most of the Linux distribution have Python 2 7 already installed Mac OS X also has Python installed by default To check the current version of Python installed on your system you can type in a terminal python version Webots will start Python using the python2 7 command line To check if this command line is installed on your computer you can type in a terminal python2 7 version More information is available from the Python official web site 3http www python org 132 CHAPTER 4 LANGUAGE SETUP Windows Instructions Webots comes with Python 2 7 64 bit pre installed in the msys 64 folder 4 6 3 Source Code o
182. lds are organized as hierarchical structures where objects can contain other objects like in VRML97 For example a robot can contain two wheels a distance sensor and a joint which itself contains a camera etc A world file doesn t contain the controller code of the robots it only specifies the name of the controller that is required for each robot Worlds are saved in wbt files The wbt files are stored in the worlds subdirectory of each Webots project 2 1 6 What is a controller A controller is a computer program that controls a robot specified in a world file Controllers can be written in any of the programming languages supported by Webots C C Java Python or MATLAB When a simulation starts Webots launches the specified controllers each as a separate process and it associates the controller processes with the simulated robots Note that several robots can use the same controller code however a distinct process will be launched for each robot Some programming languages need to be compiled C and C other languages need to be interpreted Python and MATLAB and some need to be both compiled and interpreted Java For example C and C controllers are compiled to platform dependent binary executables for example exe under Windows Python and MATLAB controllers are interpreted by the corresponding run time systems which must be installed Java controller need to be compiled to byte code class files or jar an
183. lect the DirectionalLight node and click on the Add button In the open dialog box and choose PROTO hands on Webots gt objects gt floors gt Floor Solid The newly added Floor PROTO has a default size of 10mx10m but it is possible to adjust its size its position and texture by changing the corresponding fields In the scene tree view select and expand the Floor Modify the size fields and set it to 1 1 to resize it to Imx1m hands on 7 3 3 The Solid Node This subsection introduces the most important node in Webots the Solid node But let s start with a definition A rigid body is a body in which deformation can be neglected The distance between any two given points of a rigid body remains constant in time re gardless of external forces exerted on it Soft bodies and articulated objects F are not rigid bodies e g these are not rigid bodies a rope a tyre a sponge theory and an articulated robot arm However an articulated entity can be broken into of several undividable rigid bodies For example a table a robot finger phalanx or a wheel are undividable rigid bodies The physics engine of Webots is designed for simulating rigid bodies An important steps when designing a simulation is to break up the various entities into undividable rigid bodies In Webots there is a direct matching between a rigid body and a Solid node A Solid node or a node which inherits the Solid node will
184. ler is in the WEBOTS_MODULES_PATH projects default controllers braitenberg directory 3 5 REAL ROBOTS 109 Figure 3 49 khepera3 wbt 3 5 17 khepera3 wbt Keywords DifferentialWheels DistanceSensor Braitenberg texture Khepera III In this example you can see a Khepera III robot from K Team moving inside an arena while avoiding the walls Like many other examples this one uses the braitenberg controller The source code for this controller is in the WEBOTS_MODULES_PATH projects default controllers braitenberg directory 110 CHAPTER 3 SAMPLE WEBOTS APPLICATIONS Figure 3 50 khepera_kinematic wbt 3 5 18 khepera kinematic wbt Keywords DifferentialWheels DistanceSensor Braitenberg Kinematic Khepera In this example you can see two Khepera robots from K Team moving inside an arena while avoiding each other and the walls It is a good example of how to use teh kinematic mode of Webots Like many other examples this one uses the braitenberg controller The source code for this controller is in the WEBOTS_MODULES_PATH projects default controllers braitenberg directory 3 5 REAL ROBOTS 111 Figure 3 51 khepera_gripper wbt 3 5 19 khepera_gripper wbt Keywords DifferentialWheels Gripper Khepera In this example you can see a Khepera robot from K Team equipped with a gripper The robot uses its gripper to grab a stick move a bit with it and drop it on the ground This behavior is repeated endlessly The sour
185. limb obstacles It can also turn on the spot In this example the robot will first move on its own to the center of the world then you may drive it yourself using the keyboard To find out which keys will allow you to perform these operations please read the explanation message printed at the beginning of the simulation in the Console window Because of its particular structure this model is also an example of custom ODE plugins for e how to create and manage ODE joints e how to add custom force e how to create spongy tires The source code for this controller is in the WEBOTS_MODULES_PATH projects robots shrimp controllers shrimp directory and the ODE plugin is in the WEBOTS_MODULES__ PATH projects robots shrimp plugins physics shrimp directory Inttp www bluebotics ch 122 CHAPTER 3 SAMPLE WEBOTS APPLICATIONS Figure 3 62 bioloid wbt 3 5 30 bioloid wbt Keywords Robot node legged robot RotationalMotor Bioloid Camera DistanceSensor key board modular robots walking In this example the four legged robot model figure 3 62 a corresponds to a real Bioloid robot figure 3 62 b developed by and commercially available from Tribotix This dog robot model was build from the Bioloid Comprehensive Kit Both the visual aspect and the physical properties of the real robot have been modeled The physical dimensions friction coefficients and mass distribution have been estimated after various measurements on the co
186. llows 1 entry point of the controller 2 int main int argc char x x argv ES 4 initialize the Webots API 5 wb_robot_init 6 initialize devices 7 feedback loop 8 while 1 9 step simulation 10 int delay wb_robot_step TIME_STEP 11 if delay 1 exit event from webots hands on 12 break 13 read sensors outputs 14 process behavior 15 write actuators inputs 16 17 cleanup the Webots API 18 wb_robot_cleanup 19 return 07 EXIT SUCCESS 20 A robot device is referenced by a WoDeviceTag The WoDeviceTag is retrieved by the wo_robot_get_device function Then it is used as Ne first argument in every function call concerning this device J A sensor such as the DistanceSensor has to be enabled before use The sec ond argument of the enable function defines at which rate the sensor will be refreshed theory 7 5 TUTORIAL 4 MORE ABOUT CONTROLLERS 20 MINUTES hands on hands on hands on 215 Just after the comment initialize devices get and enable the distance sensors as follows 1 initialize devices 2 lint i 3 WbDeviceTag ps 8 4 ichar ps_names 8 4 5 asp ESTA Megat SEAN 6 agg ESO Seat para 7 8 9 for i 0 1 lt 8 i 10 ps i wb_robot_get_device ps_names i 11 wb_distance_sensor_enable ps 1 TIME_STEP 12 In the main loop just after the co
187. lor field to set its color avoid to use pure colors balancing the RGB components give better results To set a Material with texture set only its ImageTexture node Eventually the specularColor field can be set to a gray value to set a reflection on the object The other fields especially the ambientIntensity and the emissiveColor fields shouldn t be modified except in specific situations The color field of the ElevationGrid shouldn t be use for a realistic rendering because it is not affected by the ambient light with the same way as the other Shapes Here is a methodology to set up the lights 1 Place the lights at the desired places Often a single directional light pointing down is sufficient 2 Set both their ambient Intensity and their intensity fields to 0 3 Increase the ambient Intensity of the main light The result will be the appearance of the objects when they are in shadows 4 Switch on the shadows if required The shadows are particularily costly and are strongly related to the Shapes resolution 5 Increase the intensity of each lamp 9 4 Speed Performance 9 4 1 Why is Webots slow on my computer You should verify your graphics driver installation Please find instructions here section 1 3 If you are using a laptop computer please check the power options and make sure you are using the high performance power plan On Ubuntu or other Linux we do also recommend to deactivate com
188. ly this robot controller if finished saveExperimentsData wb_robot_cleanup exit 0 NNR WN na Note that the exit status as well as the value returned by the main function are ignored by Webots 6 1 CONTROLLER PROGRAMMING 165 6 1 8 Shared libraries Creating shared libraries can be very useful to share code between controllers and or plugins There are several ways to do so but we recommend to place them into a subdirectory of the libraries directory of your project Indeed the environment variables of the controllers are modified to include these paths into your DY LD_LIBRARY_ PATH environment variable depending on the OS Moreover the main Makefile WEBOTS_HOME resources Make file include used to compile Webots controllers is able to create shared libraries and to link easily with the Controller libraries ODE or the Qt framework A good example of this is the Qt utility library located there WEBOTS_HOME resources pro jects libraries qt_utils If for some reason shared libraries cannot be in the libraries directory the WEBOTS_LI BRARY_PATH environment variable will be very helpful The paths it contains will be added at the beginning of the library search path DY LD_LIBRARY_ PATH when starting the con troller 6 1 9 Environment variables For some projects it will be necessary to define or change variables defined in your environment They can be changed in the settings of the computer but it m
189. m contains the source code for a simple line following system which as an exercise can be improved upon to obtain the behavior demon strated in the e puck_line_demo wbt demo in which the e puck robot is able to follow the line drawn on the floor but also to avoid obstacles and return to the line following behavior Device x m y m z m Orientation rad ps0 0 010 0 033 0 030 1 27 ps1 0 025 0 033 0 022 0 77 ps2 0 031 0 033 0 00 0 00 ps3 0 015 0 033 0 030 5 21 ps4 0 015 0 033 0 030 4 21 ps5 0 031 0 033 0 00 3 14159 ps6 0 025 0 033 0 022 2 37 ps7 0 010 0 033 0 030 1 87 camera 0 000 0 028 0 030 4 71239 Table 8 4 Devices orientations 240 CHAPTER 8 ROBOTS ps7 camera psO ps6 ps1 ledO Po ed9 4 a Na yn EP led7e AS led 1 ps5 mm ee 3 led6 n ps2 Figure 8 4 Sensors LEDs and camera afterwards This model was contributed by Jean Christophe Zufferey from the EPFL who sets up a series of exercises with Webots and extended e puck robots The directory WEBOTS_MODULES_PATH projects samples curriculum contains a rich collection of simulations involving the e puck robot You will find inside it all the worlds and controllers corresponding to the exercices of Cyberbotics robotics curriculum Written in collaboration with professors and master students of EPFL Cyberbotics curriculum is an edu cational document intended for all level of learnings in r
190. mediate compilation files in the current file s directory The source files remain untouched S Sy The Make JAR file menu item rebuilds the whole project and packs all the class ina jar This is a convenience function that can be used to pack a complete controller prior to uploading it to one of our online contest website The Cross compile menu item allows to cross compile the current text editor s file Note that a specific Makefile is required in the controller s directory for performing this operation For an e puck robot this Makefile must be named Makefile e puck The Cross compilation clean menu item allows you to clean the cross compilation files Note that a specific Makefile is required in the controller s directory for performing this operation For an e puck robot this Makefile must be named Makefile e puck 5 2 The standard File Hierarchy of a Project Some rules have to be followed in order to create a project which can be used by Webots This section describes the file hierarchy of a simple project 5 2 1 The Root Directory of a Project The root directory of a project contains at least a directory called worlds containing a single world file But several other directories are often required e controllers this directory contains the controllers available in each world files of the current project The link between the world files and this directory is done through the controller field of the Robot node explai
191. mic libraries and the 1 flag can be used to specify the name of a library that needs to be linked with the controller For example let s assume that you would like to add an external library called XYZLib And let s assume that the library s header files and d11 file are located like this Windows C Users YourName XYZLib include XYZLib h C Users YourName XYZLib lib XYZLib dll Then here is how this should be specified in the Makefile INCLUDE I C Users YourName XYZLib include LIBRARIES L C Users YourName XYZLib lib 1XYZLib The first line tells gcc where to look for the include lt XYZLib h gt file The second line tells gcc to link the executable controller with the XYZLib dl11 and where that dl 1 can be found Note that this would be similar on Linux and Mac OS X you would just need to use UNIX compatible paths instead If more external libraries are required it is always possible to use additional I L and 1 flags For more information on these flags please refer to the gcc man page Using Webots C API in a C Controller Normally C controllers use Webots C API The C API is a set of C classes provided by C header files e g include lt webots Robot hpp gt If you prefer C control lers can use Webots C API instead The C API is a set of C functions starting with the wh prefix and provided by C header files e g include lt webots robot h gt To use the C
192. mment read sensors outputs read the distance sensor values as follows read sensors outputs double ps_values 8 for i 0 1 lt 8 itt BwWN er ilj ps_values i wb_distance_sensor_get_value ps In the main loop just after the comment process behavior detect if a collision occurs i e the value returned by a distance sensor is bigger than a threshold as follows detect obstacles bool left_obstacle ps_values 0 gt 100 0 ps_values 1 gt 100 0 ps_values 2 gt 100 0 bool right_obstacle ps_values 5 gt 100 0 ps_values 6 gt 100 0 ps_values 7 gt 100 0 OANNDNBRWN Fe 216 CHAPTER 7 TUTORIALS Finally use the information about the obstacle to actuate the wheels as fol lows 1 init speeds 2 double left_speed 500 3 double right_speed 500 4 modify speeds according to obstacles 5 if left_obstacle 6 turn right 7 left_speed 500 8 right_speed 500 hands on A 10 else if right_obstacle 11 turn left 12 left_speed 500 13 right_speed 500 14 15 write actuators inputs 16 wb_differential_wheels_set_speed left_speed right_speed Compile your code by selecting the Build gt Build menu item Compilation errors are displayed in red in the console If there are any fix them and retry hands on to compile Revert the simulation 7 5 4 The Co
193. mponents of the real robot The source code for the controller of the robot as well as the model of the robot are located under the Webots installation directory in the WEBOTS_MODULES_PATH projects robots bioloid sub folder e controllers bioloid controller directory e worlds bioloid whbt world definition file containing a Bioloid dog robot Using the keyboard the user can control the quadruped robot by setting the walking direction forward or backwards and also the heading direction right or left Keyboard actions include e Right Arrow Turn right http www robotis com 3http www tribotix com 3 5 REAL ROBOTS 123 e Left Arrow Turn left e B Walk backwards e F Walk forward The walking gait used in the controller relies on an inverse kinematics model Further details are available from BIRG web site The included controller illustrates a trotting gait showing the best performance so far The turning capabilities of the robot are based on the stride length modulation When the robot is asked to turn right the stride length of the right side and left side are respectively decreased and increased During the walk the extremity of each leg is describing an ellipsoid the diameters of these ellipsoids are updated according to the stride length to allow the robot to turn either right or left Other keyboard actions are also provided to fine tune the frequency and the stride length factor Q Increase frequency
194. munication requires the usage of additional Emitters and Receivers 6 3 2 Resetting the robot When using optimization algorithm you will probably need to reset the robot after or before each fitness evaluation There are several approaches to resetting the robot Using the wb_supervisor field set_ and wb_supervisor_simulation_reset_physics func tions You can easily reset the position orientation and physics of the robot using the wo_supervi sor_field_set andwb_supervisor_simulation_reset_physics functions here is an example 1 get handles to the robot s translation and rotation fields 2 WbNodeRef robot_node wb_supervisor_node_get_from_def MY ROBOT 3 WoFieldRef trans_field wb_supervisor_node_get_field robot_node translation 4 WbFieldRef rot_field wb_supervisor_node_get_field robot_node rotation 5 6 reset the robot 7 const double INITIAL _TRANS 3 0 0 5 O 8 const double INITIAL_ROT 4 0 1 0 1 5708 9 wb_supervisor_field_set_sf_vec3f trans_field INITIAL TRANS 10 wo_supervisor_field_set_sf_rotation rot_field INITIAL ROT 11 wo_supervisor_simulation_reset_physics The drawback with the above method is that 1t only resets the robot s main position and orien tation This may be fine for some types of optimization but insufficient for others Although it is possible to add more parameters to
195. n which Aseba can be connected and it wraps the Aseba API with the Webots API Here is how to proceed to connect Aseba to the Thymio II model in Webots Make sure that the simulation is running the controller has started and that the controller of the Thymio II 8 3 USING THE THYMIO II ROBOT 231 Aseba Target Selection Y Network TCP Host Port localhost 33333 Serial Custom English Figure 8 10 Aseba Studio and VPL target selection dialog robot is thymio2_aseba You can check this from the Webots scene tree by opening the Thymio2 node Aseba Studio or VPL for Thymio II can then be started From the Aseba target selection dialog see the figure 8 10 select the Network TCP IP option with the following parameters Host localhost and Port 33333 Then just click on the Connect button In case of a simulation containing several Thymio II the TCP IP port of the thymio2_aseba controller should be unique for each robot instance This value can be modified by editing the Thymio2 controllerArgs field The Thymio II window see the figure 8 11 can help you to raise some events easily These events are mainly useful when using the VPL for Thymio II software To open the Thymio II window just double click on the 3D model of the robot 8 3 3 Thymio II Pen You can easily add a pen in the simulated model by adding a Thymio2Pen node to the Thymi 02 field This pen can draw on every 3D object This is particularily useful to p
196. na Transform O DEF Transform to Export PROTO Source Result Console a Figure 7 1 The Webots main window splits into four dockable subwindows the scene tree view on the left hand side including a panel at the bottom for editing fields values the 3D view in the center the text editor on the right hand side and the console at bottom of the window Note that some of these subwindows have a toolbar with buttons The main menus appear on the top of the main window The virtual time counter and the speedometer are displayed in the right part of the 3D view toolbar The status text is displayed in the bottom left of the main window Figure 7 2 What you should see at the end of the tutorial 7 2 TUTORIAL 1 YOUR FIRST SIMULATION IN WEBOTS 20 MINUTES 195 7 2 1 Create a new World In this subsection we will create a new simulation The content of a simulation is stored in a world file This world file contains all the information related to your simulation i e where are the objects how do they look like how do they interact with each other what is the color of the sky where is the gravity vector etc A world is defined by a tree of nodes Each node has some customizable l properties called fields A world is stored in a file having the wbt suffix F The format of this file is derived from the VRML language and is human theory readable The world files must be stored directly in the project subdir
197. nce to Webots For example by explicitly mentioning Cyberbotics web site or by referencing a journal paper that describes Webots To make this simpler we provide here some citation examples including BibTex entries that you can use in your own documents 2 7 1 Citing Cyberbotics web site This project uses Webots a commercial mobile robot simulation software developed by Cyber botics Ltd This project uses Webots http www cyberbotics com a commercial mobile robot simulation software developed by Cyberbotics Ltd The BibTex reference entry may look odd as it is very different from a standard paper citation and we want the specified fields to appear in the normal plain citation mode of LaTeX MISC Webots AUTHOR Webots TITLE http www cyberbotics com NOTE Commercial Mobile Robot Simulation Software EDITOR Cyberbotics Ltd URL http www cyberbotics com Once compiled with LaTeX it should display as follows References 1 Webots http www cyberbotics com Commercial Mobile Robot Simulation Software 2 7 2 Citing a reference journal paper about Webots A reference paper was published in the International Journal of Advanced Robotics Systems Here is the BibTex entry http www cyberbotics com 2 7 CITING WEBOTS 57 ARTICLE Webots04 AUTHOR Michel O TITLE Webots Professional Mobile Robot Simulation JOURNAL Journal of Advanc
198. ned in the reference manual More information about this directory in the following subsections e protos this directory contains the PROTO files available for all the world files of the current project e plugins this directory contains the plugins available in the current project The link between the world files and this directory is done through the physics field of the WordInfo node explained in the reference manual e worlds this directory contains the world files the project files see below and the tex tures typically in a subdirectory called textures Note that the directories can be created by using the wizard New Project Directory described in chapter 2 note 142 CHAPTER 5 DEVELOPMENT ENVIRONMENTS 5 2 2 The Project Files The project files contain information about the GUI such as the perspective These files are hidden Each world file can have one project file If the world file is named myWorldFile wbt its project file is named myWorldFile wbproj This file is written by Webots when a world is correctly closed Removing it allows you to retrieve the default perspective 5 2 3 The controllers Directory This directory contains the controllers Each controller is defined in a directory A controller is referenced by the name of the directory Here is an example of the controllers directory having one simple controller written in C which can be edited and executed controllers con
199. nformation about the Gyro node and functions in the Reference Manual Using a Supervisor Using the wb_supervisor_node_get_velocity function it is possible to retrieve both the linear and angular velocity of any Solid node You will find more information about this function in the Reference Manual Thttp ode wiki org wiki index php title Manual 264 CHAPTER 9 WEBOTS FAQ In physics plugin code In the physics plugin you can use ODE s dBodyGetLinearVel and dBodyAngularVel functions These functions return the linear velocity in meters per second respectively the angu lar velocity in radians per second Please find a description of ODE functions here here 9 2 3 How can I reset my robot Please see subsection 6 3 2 9 2 4 What does this mean Could not find controller Loading void controller instead This message means that Webots could neither find an executable file e g exe nor an in terpreted language file e g class py m to run as controller program for a robot In fact Webots needs each controller file to be stored at specific location in order to be able to executed it The requested location is in the controllers subdirectory of the current Webots project directory e g my_project Inside the controllers directory each controller project must be stored in its own directory which must be named precisely like the controller field of the Robot Inside that directory the executable
200. nnot start any more please report the bug there http www cyberbotics com bug Please include a precise description of the problem the sequence of actions necessary to re produce the problem Do also attach the world file and the controller programs necessary to reproduce it Inttp www cyberbotics com forum http www cyberbotics com reference 3http en wikibooks org wiki Cyberbotics _Robot_Curriculum http www cyberbotics com webots http www cyberbotics com bug 261 262 CHAPTER 9 WEBOTS FAQ Before reporting a bug please make sure that the problem is actually caused by Webots and not by your controller program For example a crash of the controller process usually indicates a bug in the controller code not in Webots This situation can be identified with these two symptoms 1 Webots GUI is visible and responsive but the simulation is blocked simulation time stopped 2 The controller process has vanished from the Task Manager Windows or is shows as lt defunct gt when using ps e Linux Mac 9 1 3 Is it possible to use Visual C to compile my controllers Yes However you will need to create your own project with all the necessary options You will find more detailed instructions on how to do that in section 5 6 To create the import libraries the Lib files in Visual C from the x d11 files of the lib directory of Webots please follow the instructions provided with the documentation of your com
201. node such as the Sphere node can be used in a graphical context However only a subset of them can be used in a physical context Take a look at the schema of the chapter 2 of the Reference Manual to now which primitive you can use We want now to reduce the size of the Sphere and to increase its graphical quality by increasing the number of triangles used to represent it For each Sphere node defining the ball set its radius field to 0 05 and its subdivision field to 2 Refer to the Reference Manual to understand what hands on the subdivision field stands for 7 3 6 DEF USE mechanism We will see in this subsection a mechanism which can be useful to avoid redundancy in the world files 7 3 TUTORIAL 2 MODIFICATION OF THE ENVIRONMENT 20 MINUTES theory The two Sphere definitions that we have used earlier to define the ball are redundant We will The DEF USE mechanism allows to define a node in one place and to reuse that definition elsewhere in the Scene Tree This avoids the duplication of identical nodes and this allows to modify several nodes at the same time Here is how this works first a node is labeled with a DEF string and then copies of this node are reused elsewhere with the USE keyword Only the fields of the DEF node can be edited the fields of the USE nodes assume similar values This mechanism is dependent on the apparition order of the nodes in the world file because the DEF node should appear first
202. ns are listed Some of them are only accessible in the Build menu whereas Build and Clean actions have a shortcut in the Text Editor toolbar ej Builds the whole project by invoking make in the selected file s directory With C C the Build button compiles and links the whole project into an executable file C C source file dependencies are automatically generated and updated when necessary With Java the Build button compiles the whole project into bytecode class files 139 140 CHAPTER 5 DEVELOPMENT ENVIRONMENTS rojects robots e puck controllers e puck_crosscompilation e puck_crosscompilation c OC wABS QU 43 braitenberg c EJ e puck c EJ e puck_crosscompilation c EJ o a E define NB DIST SENS 8 int main int argc char argv WbDeviceTag accelerometer WbDeviceTag led NB LEDS WbDeviceTag ps NB DIST SENS WbDeviceTag ls NB LIGHT SENS WbDeviceTag cam const double a const unsigned char im short direction 1 int it m n long int sum double count int camera width camera_height initialize Webots wb_robot_init get and enable devices char text 5 led0 for it 0 it lt NB LEDS it led it wb robot get device text text 3 wb led set led it OFF char textPS ps0 Figure 5 1 Webots Text Editor 5 2 THE STANDARD FILE HIERARCHY OF A PROJECT 141 te 2 The Clean button invokes make clean to delete the inter
203. nsure that this is the case the simplest solution is to have an open login session on 152 CHAPTER 5 DEVELOPMENT ENVIRONMENTS computer B i e to have logged in using the login screen of computer B and not having logged out Unless configured differently the ssh login and the screen login session must belong to the same user otherwise the X server will reject the connection Note that the xhost command can be used to grant access to the X server to another user For security reasons the screen of the open session on computer B can be locked e g with a screen saver this won t affect the running X server 5 7 2 Terminating the ssh session A little problem with the above approach is that closing the ssh session will kill the remote jobs including Webots Fortunately it is easy to overcome this problem by starting the Webots as a background job and redirecting its output to a file ssh myname computerB org export DISPLAY 0 0 webots mode fast stdout stderr myworld wbt amp gt out txt amp exit The amp gt sign redirects into a text file the output that would otherwise appear in the ssh terminal The amp sign starts Webots as a background job so the user can safely exit the ssh session while Webots keeps running In this case the decision to terminate the job is usually made in the Supervisor code according to simulation specific criteria The wo_supervisor_simulation_quit function can be used to a
204. ntroller Code Here is the complete code of the controller detailed in the previous subsection include lt webots robot h gt include lt webots differential_wheels h gt tinclude lt webots distance_sensor h gt time in ms of a simulation step define TIME_STEP 64 entry point of the controller int main int argc char argv Rh PB OowoAananktwhd a initialize the Webots API 12 wb_robot_init 13 7 5 TUTORIAL 4 MORE ABOUT CONTROLLERS 20 MINUTES 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 internal variables int i WbDeviceTag ps 8 char ps_names 8 4 peo Bal paz tas psi eso paso ej ed y initialize devices for i 0 1 lt 8 i ps i wb_robot_get_device ps_names i wb_distance_sensor_enable ps i TIME_STEP feedback loop while 1 step simulation int delay wb_robot_step TIME_STEP if delay 1 exit event from webots break read sensors outputs double ps_values 8 for i 0 1 lt 8 i ps_values i wb_distance_sensor_get_value ps i detect obstacles bool left_obstacle ps_values 0 gt 100 ps_values 1 gt 100 0 ps_values 2 gt 100 0 bool right_obstacle ps_values 5 gt 100 0 ps_values 6 gt 100 0 ps_values 7 gt 100 0
205. nts The first three components are a unit vector that defines the rotation axis The fourth vee component defines the rotation angle about the axis in rad The rotation occurs in the sense prescribed by the right hand rule Modify the rotation of the Solid node of the dumbbell in order to move the handle s axis y axis parallel to the ground A unit axis of 1 0 0 and an hands on angle of 7 2 is a possible solution 7 6 5 How to choose bounding Objects As said before minimizing the number of bounding objects increases the simulation speed How ever choosing the bounding objects primitives carefully is also crucial to increase the simulation speed Using a combination of Sphere Box Capsule and Cylinder nodes for defining objects is very efficient Generally speaking the efficiency of these primitives can be sorted like this Sphere gt Box gt Capsule gt Cylinder Where the Sphere is the most efficient But this can be neglected for a common usage The IndexdedFaceSet geometry primitive can also be used in a bounding object But this prim itive is less efficient than the other primitives listed above Moreover its behavior is sometimes buggy For this reasons we don t recommend using the IndexdedFaceSet when another solution using a combination of the other primitives is possible Grounds can be defined using the Plane or the ElevationGrid primitives The Plane node is much more efficient than the El
206. o access Webots objects in the physics plugin how to exchange information with the controller e how to add custom forces e how to move objects e how to handle collisions how to draw objects using OpenGL 3 3 HOW TO 89 Figure 3 30 supervisor wbt 3 3 6 supervisor wbt Keywords Supervisor DifferentialWheels soccer label import node restart simulation screen shot change controller This shows a simple soccer game with six robots and a referee The Supervisor code demon strates the usage of several Supervisor functions For example the Supervisor inserts a second ball to the simulation changes its color takes a picture of the 3D view restarts the simulation etc In addition the Supervisor also plays the role of a soccer referee it displays the current score places the players to their initial position when a goal is scored etc 90 CHAPTER 3 SAMPLE WEBOTS APPLICATIONS Figure 3 31 texture_change wbt 3 3 7 texture_change wbt Keywords Supervisor texture wb_supervisor field_set_ Camera In this example a robot moves forward and backward in front of a large textured panel The robot watches the panel with its Camera Meanwhile a Supervisor switches the image displayed on the panel 3 3 HOW TO 91 Figure 3 32 town wbt 3 3 8 town wbt Keywords Transform USE DEF This example shows a complex city model built with various Transform nodes The model makes a intensive use of the DEF and USE VR
207. o display some text in the Webots console The second argument st ream can be either WB_STDOUT or WB_STDERR depending on which stream you would like to write In order to create a cross platform controller it is recommended to use the wo_console_ print text stream onevery OS 134 CHAPTER 4 LANGUAGE SETUP 4 7 5 Compatibility Issues We recommend to use the latest Matlab version on an up to date operating system Note that 64 bit versions of Webots are not compatible with 32 bit versions of MATLAB Webots comes only in 64 bit flavour and therefore it can only inter operate with a 64 bit version of MATLAB On some platform the MATLAB interface needs perl and gcc to be installed separately These tools are required because MATLAB s loadlibrary function will need to re compile Webots header files on the fly According to MATLAB s documentation this will be the case on 64 bit systems and hence we advice 64 bit Webots users on Linux to make sure that these packages are installed on their systems On some Mac OS X systems the MATLAB interface will work only if you install the Xcode de velopment environment because gcc is required An error message like this one is a symptom of the above described problem error using gt calllib Method was not found error in gt launcher at 66 calllib libController wb_robot_init 4 8 Using ROS 4 8 1 What is ROS ROS Robot Operating Sys
208. obotics It addresses a dozen of topics ranging from finite state automata to particle swarm optimization all illustated through the real or the simulated e puck robot you can browse it here The e puck models of Webots distribution are open source and you are welcome to modify them If you develop a useful modification and would like to share it please let us know so that we can improve these models using your contribution 8 1 3 Control interface Control window When opening a world containing an e puck robot Webots displays the e puck control window which also appears when you double click on the e puck robot This window is depicted in fig ure 8 6 It allows visualizing the devices of the robot The distance measurements are displayed in red outside the body of the robot The light measurements are displayed in yellow above the 3http www cyberbotics com publications RiE2011 pdf nttp www cyberbotics com curriculum 8 1 USING THE E PUCK ROBOT 241 E z Webots Figure 8 5 An e puck extension for line following gt E puck viewer e puck camera 3934 3884 Camera 345 504 3921 3895 300 Floor Sensors Accelerometer x 0 76 3727 3830 y 1 601 439 z 10 9 Encoders devirfcommo v Befeshpots right 677 left 1254 Figure 8 6 The e puck control window for simulation 242 CHAPTER 8 ROBOTS distance measurements The 10 LEDs are displayed in black
209. ode_get_from_del MY_ROBOT 13 WbFieldRef trans_field wb_supervisor_node_get_field robot_node translation Fh 14 13 double a D E 16 for a 0 0 a lt 520 a 0 2 4 17 for b 0 0 b lt 10 0 b 0 3 18 evaluate robot during 60 seconds simulation time 19 for t 0 0 t lt 60 0 t TIME_STEP 1000 0 20 actuateMotors a b t 21 wb_robot_step TIME_STEP 22 23 24 compute travelled distance 25 const double pos wb_supervisor_field_get_sf_vec3f trans_field 26 double dist sqrt pos 0 pos 0 pos 2 pos 2 21 printf a g b g_ gt _dist sg n a b dist 28 29 reset robot position 30 const double INITIAL 3 0 0 5 O 31 wb_supervisor_field_set_sf_vec3f trans_field INITIAL 32 33 34 35 return 0 36 As in the previous example the trans_field variable is a WoFieldRef that identifies the translation field of the robot In this example the trans_field is used both for getting 6 3 USING NUMERICAL OPTIMIZATION METHODS 171 wb_supervisor_field_get_sf_vec3f and for setting wo_supervisor_field_ set_sf_vec3f the field s value Please note that the program structure is composed of three nested for loops The two outer loops change the values of the a and b parameters The innermost loop makes the robot walk during 60 seconds One important point here is th
210. oller cpp IS WEBOTS_HOME include Wall IS WEBOTS_HOME include controller c DLINUX find_library CPP_CONTROLLER_LIBRARY CppController WEBOTS_HOME 11b hands on find_library C_CONTROLLER_LIBRARY Controller S WEBOTS_HOME 11b target_link_libraries webots_joystick_node catkin_ LIBRARIES S C_CONTROLLER_LIBRARY CPP_ CONTROLLER _LIBRARY These lines tell catkin where to find the Webots controller libraries and to link the webot s_joystick_node against them The comments indicate where to paste these lines appropriately the distributed CMakeLists txt file shows you the right places Build the webots_joystick package Then copy the resulting ROS node exe cutable at the root of controllers joystick and rename it appropri ately cd my_ros controllers joystick catkin_ws S catkin_make cp devel lib webots_joystick webots_joystick_node my_ros controllers joystick joystick hands on Calling catkin_make created the directories catkin_ws build and catkin_ws devel You should source catkin_ws devel setup bash if you want to use ROS built in commands to manage the webot s_ joystick package note Have a look at the file WEBOTS_MODULES_PATH projects languages ros controllers joystick Makefile This file allows you to re compile the joystick controller from Webots build hands on editor edit the source file in Webots build editor and hit the build button You may take inspiration from it when b
211. omes with some implementations and usage examples for these plugins You will find more info on this topic in Webots Reference Manual Chapter 7 Tutorials The aim of this chapter is to explain the fundamental concepts of Webots required to create your own simulations Learning is focused on the modeling of robots and of their environment as well as on the programming of robot controllers You will also learn where to find the documentation to go further This chapter is suitable for absolute beginners in Webots A background in programming is nev ertheless required The examples are written in C language If you are not familiar with the C language you should be able to understand this chapter anyway because the C programs below are very simple Except for programming you don t need any particular knowledge to go through the tutorials included in this chapter However a basic background knowledge in robotics mathe matics modeling and tree representation might turn out to be helpful Experienced Webots users may skip the first tutorials However we would recommend them to read at least the introduction and conclusion of these tutorials Each section of this chapter except the first one and the last one is a tutorial Each tutorial has a precise educational objective explained in the first paragraph The acquired concepts are then summarized in the conclusion subsection A tutorial is designed as a sequence of interactive steps The kno
212. onalMotor IndexedLineSet USE DEF DifferentialWheels In this example a light robot light blue is lifted over two heavier robots dark blue All three robots are equipped with a Connector placed at the tip of a moveable handle HingeJoint An IndexedLineSet is added to every Connector in order to show the axes When the simulation starts the light robot approaches the first heavy robot and their connectors dock to each other Then both robots rotate their handles simultaneously and hence the light robot gets passed over the heavy one Then the light robot gets passed over another time the second heavy robot and so on All the robots in this simulation use the same controller the different behaviors are selected according to the robot s name 3 2 WEBOTS DEVICES 75 Figure 3 16 distance_sensor wbt 3 2 5 distance sensor wbt Keywords DistanceSensor Braitenberg DifferentialWheels In this example a robot has eight DistanceSensors placed at regular intervals around its body The robot avoids obstacles using the Braitenberg technique 76 CHAPTER 3 SAMPLE WEBOTS APPLICATIONS Figure 3 17 emitter_receiver wbt 3 2 6 emitter_receiver wbt Keywords DifferentialWheels Emitter Receiver infra red transmission USE DEF In this example there are two robots one is equipped with an Emitter the other one with a Receiver Both robots move among the obstacles while the emitter robot sends messages to the receiver rob
213. ons for setting the LEDs states A red button means the LED is turned on a black one means it is turned off and a grey one means there is no modification The sensor available in BotStudio are the distance sensors and the camera Moreover a timer can be used to temporize the conditions by dragging the corresponding slider Conditions over the IR sensors can be set by dragging the 8 red sliders A condition can be reversed by clicking on the grey part of the slider Finally the camera is used for giving a clue on the front environment of the e puck An algorithm is applied on the last line of the camera and returns a integer between 10 and 10 indicating if a black line is perceived respectively at the left and at the right of the e puck field of view A condition can be set on this value for getting a line follower behavior BotStudio is depicted in the figure 8 7 An example of BotStudio can be found by opening the WEBOTS_MODULES_PATH projects robots e puck world e puck_botstudio wbt world file The BotStudio windows appears when the e puck s controller points on a bsg file Bluetooth setup The e puck has a Bluetooth interface allowing it to communicate with Webots This feature is available under Windows Linux and Mac OS X The Bluetooth interface must be set up accord 8 1 USING THE E PUCK ROBOT 243 BotStudio e puck obstacle bsg 0889 HO amp x Remote Control Simulation e puck viewer Figure 8 7
214. open the source file in the text editor hands on The new C source file is displayed in Webots text editor window This C file can be compiled without any modification however the code has no real effect We will now link the E puck node with the new controller before modifying it Link the E puck node with the e puck_go forward controller This can be done in the scene tree view by selecting the controller field of the E puck node then use the field editor at the bottom of the scene tree view push hands on the Select button and then select e puck_go_forward in the list Once the controller is linked save the world 200 CHAPTER 7 TUTORIALS Modify the program by inserting an include statement include lt webots differential_wheels h gt and by applying a differen tial wheels command wo differential wheels set speed 100 100 1 include lt webots robot h gt 2 3 Added a new include file 4 include lt webots differential wheels h gt s 6 define TIME_STEP 64 7 8 int main int argc char x x argv 91 10 wb_robot_init hands on 11 12 set up the speeds 13 wb_differential wheels_set_speed 100 100 14 15 do 16 while wb_robot_step TIME_STEP 1 17 18 wb_robot_cleanup 19 20 return 0 21 Save the modified source code File gt Save Text File and compile it Build gt Build Fix any compilation error if necessary When We
215. ops and worm like configurations while changing their mode of locomotion All modules use the same controller code but their actual module behaviour is chosen according to the name of the module 70 CHAPTER 3 SAMPLE WEBOTS APPLICATIONS Figure 3 11 stewart_platform wbt 3 1 11 stewart platform wbt Keywords Stewart platform linear motion physics plugin ball joint universal joint This is an example of a Stewart platform A Stewart platform is a kind of parallel manipulator that uses an octahedral assembly of linear actuators It has six degrees of freedom x y z pitch roll and yaw In this example the Stewart platform is loaded with a few stacked boxes then the platform moves and the boxes stumble apart This simulation attaches both ends of the linear actuators hydraulic pistons to the lower and the upper parts of the Stewart platform 3 2 WEBOTS DEVICES 71 Figure 3 12 battery wbt 3 2 Webots Devices This section provides a simple example for each Webots device The world files are located in the WEBOTS_MODULES_PATH projects samples devices worlds directory and their controllers in the WEBOTS_MODULES_PATH projects samples devices controllers directory The world files and the corresponding controller are named according to the device they exemplify 3 2 1 battery wbt Keywords Battery Charger DifferentialWheels In this example a robot moves in a closed arena The energy consumed by the wheel motors
216. or view 6 6 4 Motion editor A motion is a chronological sequence of robot poses A pose is defined by a set of commands in position of the robot motors The motion is stored in a motion file in a user readable format The controller API allows to play easily the motion files on your robot You can get the complete motion API in the reference manual The motion editor cf the figure 6 4 is a GUI helping to create motions which can be played by a robot It is implemented in the Qt utils library and is embedded inside the generic robot window plugin This implies that the motion editor is accessible only if the robot is linked cf the Robot robotWindow field with either the generic window or on a window using the Qt utils library s corresponding widget In the motion editor different fonts and colors are used to identify the status of poses and motor states modified items are displayed using bold font disabled states are written in gray and items with values outside the valid motor position range are written in red 188 CHAPTER 6 PROGRAMMING FUNDAMENTALS 6 6 5 Remote control Plugin A remote control plugin allow to simply and efficiently create an interface using the Webots API to communicate with a real robot The main purpose of a remote control library is to wrap all the Webots API functions used by the robot with a protocol communicating to the real robot Generally a program client runs on the real robot and decodes the
217. ore enter ing and after leaving the controller code If the MATLAB code uses graphics it is necessary to call the drawnow command somewhere in the control loop in order to flush the graphics Here is a simple MATLAB controller example UN PWN od Ae o uncomment the next two lines to use the desktop desktop skeyboard TIME_STEP 32 182 CHAPTER 6 PROGRAMMING FUNDAMENTALS 6 7 my_led wb_robot_get_device my_led 8 my_sensor wb_robot_get_device my_sensor 9 10 wo_distance_sensor_enable my_sensor TIME_STEP Il 12 while wb_robot_step TIME_STEP 1 13 read the sensors 14 val wb_distance_sensor_get_value my_sensor 15 16 Process sensor data here 17 18 send actuator commands 19 wb_led_set my_led 1 20 2i uncomment the next line if there s graphics to flush 22 drawnow 23 end 6 5 1 Using the MATLAB desktop In order to avoid cluttering the desktop with too many windows Webots starts MATLAB with the nodesktop option The nodesktop option starts MATLAB without user interface and there fore it keeps the memory usage low which is useful in particular for multi robot experiments If you would like to use the MATLAB desktop to interact with your controller you just need to add these two MATLAB commands somewhere at the beginning of your controller m file 1 desktop keyboard The desktop command brings up th
218. ot The range of the Emitter device is indicated by the radius of the transparent sphere around the emitter robot The state of the communication between the two robots is dis played in the Console You can observe that when the receiver robot enters the receiver s sphere and that at the same time there is no obstacle between the robots then the communication is established otherwise the communication is interrupted Note that the communication between infra red Emitters and Receivers can be blocked by an obstacle this is not the case with radio Emitters and Receivers 3 2 WEBOTS DEVICES 77 Figure 3 18 encoders wbt 3 2 7 encoders wbt Keywords DifferentialWheels encoders This example demonstrates the usage of the wheel encoders of Dif ferentialWheels robots The controller randomly chooses target encoder positions then it rotates its wheels until the en coder values reach the chosen target position Then the encoders are reset and the controller chooses new random values The robot does not pay any attention to obstacles 78 CHAPTER 3 SAMPLE WEBOTS APPLICATIONS Figure 3 19 force_sensor wbt 3 2 8 force_sensor wbt Keywords Force TouchSensor DifferentialWheels This example is nearly the same as bumper wot see subsection 3 2 2 The only difference is that this robot uses a force TouchSensor instead of a bumper So this robot can measure the force of each collision which is printed in t
219. ots supervisor h gt define TIME_STEP 5 int main wb_robot_init ZA OD U4uhluyNn a 172 CHAPTER 6 PROGRAMMING FUNDAMENTALS 8 double a b time 9 for a 0 5 a lt 10 0 a 0 1 10 for b 0 1 b lt 5 0 b 0 5 11 resetRobot move robot to initial position 12 13 run robot simulation for 30 seconds 14 for time 0 0 time lt 30 0 time TIME_STEP 1000 0 15 actuateMotors a b time 16 wb_robot_step TIME_STEP 17 18 19 compute and print fitness 20 double fitness computeFitness 21 printf with parameters g_ g fitness was g n a b fitness 22 23 24 25 wb_robot_cleanup 26 return 0 27 In this example the robot runs for 30 simulated seconds and then the fitness is evaluated and the robot is moved back to it initial position Note that this controller needs to be executed in a Supervisor in order to access the wo_supervisor_field_x functions that are necessary to read and reset the robot s position So when using this approach the robot must be based on a Supervisor node in the Scene Tree Note that this approach is not suitable to optimize a DifferentialWheels robot because due to the class hierarchy a robot cannot be aDifferentialWheels anda Supervisor at the same time Using two distinct types of controllers If on the contrary your simulation requires the simultaneous execution of severa
220. p etc source files to your project Now you should be able to build your controller with the Build gt Build MyController menu item or the F7 key This should generate the MyProject controllers MyController MyController exe file 5 7 STARTING WEBOTS REMOTELY SSH 151 7 Now we can switch to Webots in order to test the exe controller Start Webots and ver ify that your robot is associated with the correct controller In the Scene tree expand the robot node and check the controller field It should be controller MyCon troller Otherwise you should change it hit the ellipsis button this opens a selection dialog In the selection dialog choose MyController Then hit the Save button in Webots main window Finally you can hit the Run button to start the simulation At this point the simulation should be using your Visual C controller 8 If you want to debug your controller with Visual C you can attach the debugger to the running controller process Proceed like this In Webots hit the Pause button then the Revert button Then in Visual C use the Debug gt Attach to Process menu In the dialog choose the MyController exe_webots process Still in Visual C you can now add breakpoints and watches in the controller code Then in Webots hit the Run button to resume the simulation Now the controller should pause when it reaches one of your breakpoints 5 7 Starting Webots Remotely ssh Webots can be s
221. piled the controller hit the Pause and Revert buttons This pauses the simulation and reloads the freshly compiled versions of the controller Now find the process ID PID of the soccer_ supervisor process using ps e Linux orps x Mac OS X or using the Task Manager Windows The PID is in the left most column of output of ps as shown above Then open a terminal and start the debugger by typing gdb gdb attach PID gdb cont Continuing Where PID stands for the PID of the soccer_supervisor process The attach command will attach the debugger to the soccer_supervisor process and interrupt its execution Then the cont command will instruct the debugger to resume the execution of the process On Windows you will need to install the gdb exe file separately and use an MSYS console to achieve this Then hit the Run button to start the simulation and let it run until the controller crashes again The controller s execution can be interrupted at any time Ctrl C in order to query variables set up break points etc When the crash occurs gdb prints a diagnostic message similar to this Program received signal SIGSEGV Segmentation fault Switching to Thread 1208314144 LWP 16448 Ox00cd6dd5 in _TO_str_overflow_internal from lib tls libc so 6 This indicates the location of the problem You can examine the call stack more precisely by using the where command of gdb For example type gdb where 0 Ox00c
222. piler 9 2 Programming 9 2 1 How can I get the 3D position of a robot object There are different functions depending whether this information must be accessed in the con troller in the Supervisor or in the physics plugin Note that Webots PRO is required for using Supervisor and the physics plugin functions All the functions described below will return the 3D position in meters and expressed in the global world coordinate system Clearly the position of a robot can also be approximated by using odometry or SLAM techniques This is usually more realistic because most robots don t have a GPS and therefore have no mean of precisely determining their position You will find more info about odometry and SLAM techniques in Cyberbotics Robot Curriculum In controller code To get the position of a robot in the robot s controller code add a GPS node to the robot then use wbh_robot_get_device wb_gps enable and wo_gps_get_values functions Note that the GP S s resolution field must be O the default otherwise the results will be noisy You will find more info about the GPS node and functions in Reference Manual Note that the GPS can also be placed on a robot s part arm foot etc to get the world global coordinates of that particular part http www cyberbotics com reference 9 2 PROGRAMMING 263 In Supervisor code 1 To get the 3D position of any Transform or derived node in the Supervisor code yo
223. piz System gt Preferences gt Appearance gt Visual Effects None Depending on the graphics hardware there may be a huge performance drop of the rendering system up to 10x when compiz is on 9 4 2 How can I change the speed of the simulation There are several ways to increase the simulation speed 274 CHAPTER 9 WEBOTS FAQ Use the Run button Webots PRO only This button runs the simulation as fast as possible using all the available CPU power Otherwise using the Real Time running mode Webots may not be using all the available CPU power in order to obtain a simulation speed that is close to the speed of the real world s phenomena Use the Fast button Webots PRO only This button runs the simulation as fast as possible using all the available CPU power In this mode the simulation speed is increased further by leaving out the graphics rendering hence the 3d window is black Increase the value of WorldInfo basicTimeStep This field sets the granularity of the physics simulation With a higher Wor1dInfo basicTimeStep the simula tion becomes faster but less accurate With a lower WorldInfo basicTimeStep the simulation becomes slower but more accurate There is an additional restriction World Info basicTimeStep must be chosen such as to be an integer divisor of the control step which is the value passed as parameter to the wo_robot_step or equivalent function Decrease the value of Worl
224. problem This can be achieved on Ubuntu Linux from the System menu Preferences gt Appearance gt Visual Effects gt None 10 3 2 ssh x There are known issues about running Webots over a ssh x x tunneling connection This problem is not specific to Webots but to most GLX OpenGL on the X Window system appli cations that use complex OpenGL graphics We think this is caused by incomplete or defective implementation of the GLX support in the graphics drivers on Linux It may help to run the ssh x tunnel across two computers with the same graphics hardware e g both nVidia or both ATI It also usually works to use Mesa OpenGL on both sides of the ssh x tunnel however this solution is extremely slow
225. r in order to be able to open HTML X3DOM files locally e g not from the Web you may need to allow Chrome to open lo cal files referred to by the HTML X3DOM file e g textures This can be note achieved by passing the allow file access from files option at Chrome startup Otherwise textures won t show up in the 3D models e The Make HTML5 Animation item allows you to record a simulation as a 3D animation and publish it on a HTMLS web page The result is similar to a movie with playback controls except that you can change the viewpoint at any time Several files are generated an X3D file containing the 3D scene a JSON file containing the animation data and a HTML3 file displaying the result using X3DOM and Query Once the animation recording is started this item is changed to Stop HTML5 Animation and can be used to stop the animation recording The Quit Webots terminates the current simulation and closes Webots 2 3 2 Edit Menu The Edit menu provides usual text edition functions to manipulate files opened in the Text editor such as Copy Paste Cut etc 2 3 3 View Menu The View menu allows to control the viewing in the simulation window The Follow Object menu item allows to switch between a fixed static viewpoint and a viewpoint that follows a mobile object usually a robot If you want the viewpoint to follow an object first you need to select the object with the mouse and then check the Follow Objec
226. r hard disk where you have the writing rights for example your My Documents di rectory Create there a directory that will contain all your Webots projects hands i AR and name it my_webots_projects 7 1 3 Start Webots You need to learn how to launch Webots Start Webots by following the instructions given in section 2 2 If it s the first time you start Webots a welcome dialog box invites you to choose a demo simulation Choose any of them but it s a good opportunity to hands on take a look at our guided tour also available using the Help gt Webots Guided Tour menu Now a simulation is running 7 2 TUTORIAL 1 YOUR FIRST SIMULATION IN WEBOTS 20 MINUTES 193 7 1 4 Create a new Project The freshly created my_webots_projects directory will contain all your Webots projects Your first Webots project will be the tutorials of this chapter So let s create now a project named tutorials which will contain all the simulations of this chapter As mentioned earlier in this chapter the solutions of the tutorials are included in the WEBOTS_MODULES_PATH projects samples tutorials subdirectory of Webots Don t look at it now Hopefully your own tutorials directory should be pretty similar to that one at the end note A project is a directory containing all the files related to a set of simulations It is the highest container in Webots Two simulations should reside in the
227. re this section When using C C or Java the presence of a Makefile in the controller directory is neces sary If the Makefile is missing Webots will automatically propose to create one This Makefile can be modified with a text editor its purpose is to define project specific variables and to in clude the global Makefile include file The global Makefile include file is stored in WEBOTS_HOME resources directory it contains the effective build rules and may vary with the Webots version Note that Webots Makefiles are platform and language independent 5 4 2 Controller with Several Source Files C C If a controller requires several C C source files they need to be specified in the Makefile The name of each source file must be listed using one of these variables Variable Usage C_SOURCES Specifies a list of c sources files CXX_SOURCES Specifies a list of cpp cc or c source files Table 5 1 Webots Makefile Variables Every source file specified using these variables will be added to the controller build In addition dependency files will be automatically generated by the make command in order to minimize the build Note that these variables should not be used in any language other than C or C For example if a controller has several c source files then this can be specified like this in the controller s Makefile C_SOURCES my_controller c my_second_file c my_third_file c If a project h
228. rection of the positive z axis The axle s direction is given by the positive x axis Proximity sensors light sensors and LEDs are numbered clockwise their location and orientation are shown in table 8 3 and table 8 4 The last column of table 8 4 lists the angles between the negative x axis and the direction http www cyberbotics com reference 8 1 USING THE E PUCK ROBOT 237 Feature Description Size 7 4 cm in diameter 4 5 cm high Weight 150 g Battery about 3 hours with the provided 5Wh LiION rechargeable battery Processor Microchip dsPIC 30F6014A 60MHz about 15 MIPS Motors 2 stepper motors with 20 steps per revolution and a 50 1 reduction gear IR sensors 8 infra red sensors measuring ambient light and proximity of obstacles in a 4 cm range Camera color camera with a maximum resolution of 640x480 typical use 52x39 or 640x1 Microphones 3 omni directional microphones for sound localization Accelerometer 3D accelerometer along the X Y and Z axis LEDs 8 red LEDs on the ring and one green LED on the body Speaker on board speaker capable of playing WAV or tone sounds Switch 16 position rotating switch Bluetooth Bluetooth for robot computer and robot robot wireless communication Remote Control infra red LED for receiving standard remote control commands Expansion bus expansion bus to add new possibilities to your robot Programming C programming with the GNU
229. rence manual The controller plugin run in the main thread of the process also known as GUI thread the same as the controller executable This implies that if an entry point of a plugin is blocking the controller will also be blocked And if the plugin crashes the controller is also crashed The search algorithm to convert the robotWindow and the remoteControl to an existing path is explained in the reference manual Each distributed shared library is built thanks to the main Makefile the same as the one used to build the controllers WEBOTS_HOME resources Makefile include 6 6 2 Robot Window Plugin A robot window plugin allows the programmer to efficiently create custom robot windows Robot windows can be opened by double clicking on the virtual robot or by selecting the Robot Show Robot Window menu item The robotWindow field of the Robot node specifies a robot window cf documentation in the reference manual 6 6 CONTROLLER PLUGIN 185 The entry points of a robot window controller plugin are e bool whw_init This is the first function called by libController Its aim is to initialize the graphical user interface without showing it e void wbw_cleanup This is the last function called by libController Its aim is to cleanup the library destroy the GUI release the memory store the current library state etc e void whw_pre_update_gui This function is called before wow_update_gui to inform its imminent c
230. roller when it starts They are specified in the controllerArgs field of the Robot Supervisor or Dif ferentialWheels node and they are passed as parameters of the main function For example this can be used to specify parameters that vary for each robot s controller For example if we have 6 1 CONTROLLER PROGRAMMING Robot controllerArgs one two three and if the controller name is demo then this sample controller code 163 1 finclude lt webots robot h gt 2 include lt stdio h gt 3 4 int main int argc const char argv wb_robot_init 6 7 int 1 8 for i 0 i lt argc i 9 printf argv i s n i argv i 10 11 return 0 12 will print argv 0 demo argv 1 one argv 2 two argv 3 three 6 1 7 Controller Termination Usually a controller process runs in an endless loop it is terminated killed by Webots when the user reverts reloads the simulation or quits Webots The controller cannot prevent its own termination but it can be notified shortly before this happens The wb_robot_step function returns 1 when the process is going to be terminated by Webots Then the controller has 1 second clock time to save important data close files etc before it is effectively killed by Webots Here is an example that shows how to detect the upcoming termination finclude lt webots robot h gt include lt webots distance_sensor h gt include lt stdio h
231. rs Ground sensors can be added to a real e puck robot by inserting a special extension card with three sensors just below the 238 CHAPTER 8 ROBOTS Figure 8 2 The e puck model in Webots 4095 A T r Noise Sensor output value 3474 2211 676 306 34 O 001 0 02 0 03 0 04 0 05 0 06 0 07 Figure 8 3 Proximity sensor response against distance 239 8 1 USING THE E PUCK ROBOT Device Name Differential wheels differential wheels Proximity sensors ps0 to ps7 Light sensors IsO to 157 LEDs ledO to led7 e puck ring led8 body and led9 front Camera camera Accelerometer accelerometer Ground sensors extension gs0 gsl and gs2 Table 8 2 Devices names Main specifications Values Robot radius 37 mm Wheel radius 20 5 mm Axle length 52 mm Encoder resolution 159 23 Speed unit 0 00628 rad s Maximum angular speed 1000 units Table 8 3 e puck specifications camera of the robot These sensors are actually simple infra red sensors which allow the e puck robot to see the color level of the ground at three locations in a line across its front The groundSensorSlot field of the standard E puck PROTO is expressly provided for equipping the simulated e puck robot with the ground sensors extension modeled in the E puckGroundSensors PROTO This is particularly useful for implementing line following behaviors The e puck_line controller progra
232. rs the first step is to include the API module corresponding to the RotationalMotor node 1 include lt webots motor h gt Then to get the references of the RotationalMotor nodes initialize motors WbDeviceTag wheels 4 char wheels_names 4 8 wheel1 wheel2 wheel3 wheel4 y for i 0 i lt 4 i wheels i wb_robot_get_device wheels_names i 1 ADO Uu PWN Re note A motor can be actuated by setting its position its velocity its acceleration or its force cf Reference Manual Here we are interested in setting its velocity This can be achieve by setting its position at infinity and by bounding its velocity l double speed 1 5 rad s wb_motor_set_position wheels 0 INFINITY 3 wb_motor_set_velocity wheels 0 speed Implement a controller called 4 wheels_collision_avoidance moving the robot and avoiding obstacles by detecting them by the distance Sensors Note that the lookupTable field of the DistanceSensor nodes indicates which values are returned by the sensor cf Reference Manual hands on Don t forget to set the controller field of the Robot node to indicate your new controller As usual a possible solution of this exercise is located in the tutorials direc tory 7 7 6 Conclusion You are now able to design simple robot models to implement them and to create their control lers More specifically you learnt the d
233. ry Webots automatically starts MATLAB when it detects an m file in a controller directory Note that the m file must be named after its directory in order to be identi fied as a controller file by Webots So for example if the directory is named my_controller then the controller m file must be named my_controller my_controller m No special initialization code is necessary in the controller m file In fact Webots calls an in termediate launcher m file that sets up the Webots controller environment and then calls the controller m file In particular the Launcher m file loads the library for communicating with Webots and adds the path to API m files The MATLAB API m files are located in the http www mathworks com 4 7 USING MATLAB 133 lib mat lab directory of Webots distribution These are readable source files please report any problem or possible improvement about these files 4 7 3 MATLAB Installation In order to use MATLAB controllers in Webots the MATLAB software must be installed The MathWorks license required Webots must be able to access the mat lab executable usually a script in order to run controller m files Webots looks for the matlab executable in every directory of your PATH or Path on Windows environment variable Note that this is similar to calling mat 1ab from a terminal or Command Prompt on Windows therefore if MATLAB can be started from a terminal then it can also be s
234. s 3 read_sensors params 6 compute_behavior params 7 actuate_motors params 8 9 10 void evaluate_next_robot 11 const double params optimizer_get_next_parameters 12 TE 13 run robot for 30 seconds 14 double time 15 for time 0 0 time lt 30 0 time TIME STEP 1000 0 16 run_robot params i wb_robot_step TIME_STEP 18 19 td 20 compute and store fitness 21 double fitness compute_fitness 22 optimizer_set_fitness fitness 23 Sou 24 save complete optimization state to a file 25 optimizer_save_state my_state_file txt 26 La 27 start next evaluation 28 wb_supervisor_simulation_revert 29 wb_robot_step TIME_STEP 30 exit 0 31 6 3 USING NUMERICAL OPTIMIZATION METHODS 175 32 33 int main 34 wb_robot_init 35 isi 36 reload complete optimization state 37 optimizer_load_state my_state_file txt 38 kra 39 if optimizer_has_more_parameters 40 evaluate_next_robot 41 zak 42 wb_robot_cleanup 43 return 0 44 If this technique is used with Genetic Algorithms for example then the function optimizer save_state should save at least all the genotypes and fitness results of the current GA population If this technique is used with Particle Swarm Optimization then the opt imizer_ save_state function should at least save the position velocity and fitness of all particle
235. s currently in the swarm By starting and quitting Webots Finally the last method is to start and quit the Webots program for each parameter evaluation This may sound like an overhead but in fact Webots startup time is usually very short compared to the time necessary to evaluate a controller so this approach makes perfectly sense For example Webots can be called from a shell script or from any type of program suitable for running the optimization algorithm Starting Webots each time does clearly revert the simulation completely so each robot will start from the same initial state The drawback of this method is that the optimization algorithm has to be programmed outside of Webots This external program can be written in any programming language e g shell script C PHP perl etc provided that there is a way to call webots and wait for its termination e g like the C standard system does On the contrary the parameter evaluation must be implemented in a Webots controller With this approach the optimization algorithm and the robot controller s run in separate system processes but they must communicate with each other in order to exchange parameter sets and fitness results One simple way is to make them communicate by using text files For example the optimization algorithm can write the genotypes values into a text file then call Webots When Webots starts the robot controller reads the genotype file and carries out the paramet
236. s this field show you which device it refers to service topic_name this field is equal or really close to the Webots function it corre sponds For topics it is followed by the sampling period For services it is also the name of the corresponding srv file Using the Standard Controller The controller is pre compiled and you shouldn t edit it All you have to do is to load it on your robot you will find it in the default list of controller In order to use it you will have to build a ROS node that will communicates with the robot using the different services available Good examples of such ROS node can be found inside Webots at WEBOTS_MODULES_PATH 136 CHAPTER 4 LANGUAGE SETUP projects languages ros nodes In this folder you will find useful instructions to help you If you wants to access the controller from another machine and the roscore isn t running on the same machine as Webots you will need to edit the ROS_ MASTER_URI variable This can be done by editing your environment vari ables adding the address in the controller arguments in Webots or with a runtime ini file in the controller directory You must also be able to connect to each of the computer in ssh in both ways As ROS uses the hostname to find other computer devices on the network you must had other computers hostname and the associated IP address to the known hosts of each computer You can find this list in a file named hosts On Linux distribut
237. s 249 Bol Thymio H model 2 cease eee Se Oe RES ROS RRS VRE ES 249 8 3 2 Connect Aseba tothe Thymio H model 2 4 42 ee ee ess oes 250 Boer A saoe seoa m oe 8 od be dele ole Bele hate amp aoe 2 251 6 34 Thymio Ball o a sers a a eera eae eee eee oe ee OS 253 8 4 Using the Pioneer 3 AT and Pioneer 3 DX robots 233 SA Pioneer3 AT rr ARA A AA AAA AR A A 233 542 Pioneers DX os ca si al ae e Begs gob El Se A a 256 9 Webots FAQ 261 Ol General FAQ o a a e Bae e ae eH a 261 9 1 1 What are the differences between Webots PRO Webots EDU and other Webots modules occipital a 261 9 1 2 How can I report a bug in Webots lt o o 261 9 1 3 Is it possible to use Visual C to compile my controllers 262 2 POOR ci Bek eee a e 262 9 2 1 How can I get the 3D position of arobot object 262 9 2 2 How can I get the linear angular speed velocity of a robot object 263 9 2 3 How can reset miy robot lt o soen os Soh ak eh eH OY 264 9 2 4 What does this mean Could not find controller Loading void con Woller mstead Tek ak eR Ke RR e 264 9 2 5 What does this mean Warning invalid WbDeviceTag in API function 18 CONTENTS 9 2 6 Is it possible to apply a user specified force to a robot 266 9 2 7 How can I draw inthe 3D window 2 2 2 e ee ew eee ee ws 267 9 2 8 What does this mean The time step used by controller is not a multiple of WorldInfo basicTimeS
238. s and Display Devices items in Robot menu 2 4 7 Show Camera and Display images in separate window Overlay images can also be displayed outside the 3D window see figure 2 7 When double clicking with the left mouse button on the overlay a new external window displaying the device image is created and the overlay in the 3D window is disabled It is possible to restore the 3D window overlay simply by closing the window 2 4 THE 3D WINDOW 51 Figure 2 5 Camera and Display overlays Figure 2 6 Camera overlay resizing 52 CHAPTER 2 GETTING STARTED WITH WEBOTS Simulation View MyBot camera O GBBOS SBO I p W W 0 00 35 488 1 01x SolidBox SolidBox ae gt Y DEF GREEN_BOX Solid gt DEF BLUE_BOX Solid gt DEF WHITE_BOX Solid DEF PINK_BOX Solid gt DEF MYBOT Differentialwheels v Supervisor translation 000 8 rotationo100 scale 111 children DEF GROUND Display name supervisor model 16 include 17 include 18 include 19 include 28 include AAA Figure 2 7 Camera and Display image window 2 5 The Scene Tree As seen in the previous section to access to the Scene Tree Window you can either choose Scene Tree in the Tools menu or press the Show Scene Tree button in the main toolbar The scene tree contains the information that describes a simulated world including robots and environment and its graphical representation The scene tree of Webots is str
239. s been designed as follow Every entities the controller the remote control library and the robot window library should only call the libController interface Webots API func tions The controller should not be aware of its robot window and its real robot for modularity reasons The only exception is about the robot window library which can be aware of the re mote control library to initialise and monitor it This can be done trough the libController API 184 CHAPTER 6 PROGRAMMING FUNDAMENTALS Controller thread Webots fans ll i r aj una Real robot Figure 6 3 Controller plugin overview through the wb_robot_get_mode wb_robot_set mode and the wo remote con trol custom function functions Of course these rules can be easily broken because every entities runs into the same process However we recommend to respect them to get a good design The controller plugins have been designed to be written in C C because the result should be a dynamic library However it s certainly possible to write them in other languages using a C C wrapper inbetween After its loading some controller plugin functions entry points are called by libController A set of entry points have to be defined to let the controller plugin work smoothly Some of these entry points are required and some are optional The Robot node defines the location of the controller plugin through its robotWindow and its remoteControl fields cf refe
240. s can be specified at a time the other should be set to 1 j When the mass is specified it defines the total mass of the solid in kg When the density is specified its value in kg m3 is multiplied by the theory volume of the bounding objects and the product gives the total mass of the solid A density of 1000 kg m corresponds to the density of water default value Set the mass of the dumbbell to 2 kg The density is not used and should be set to 1 hands on the translation field of the solid The center of mass can be modified using the centerOfMass field of the Physics node The center of mass is specified relatively to the origin of the Solid F By default the center of mass of a Solid node is set at its origin defined by theory 7 6 TUTORIAL 5 COMPOUND SOLID AND PHYSICS ATTRIBUTES 15 MINUTES 221 Let s say that one of the weights is heavier than the other one Move the center of mass of the dumbbell of 0 01 m along the y axis hands on Note that when the solid is selected the center of mass is represented in the 3D view by a coordinate system which is darker than the coordinate system note representing the solid center 7 6 4 The Rotation Field The rotation field of the Transform node determines the rotation of this node and of its children using the Euler axis and angle representation Ne A Euler axis and angle rotation is defined by four compone
241. s languages ros worlds joystick wbt into my_ros worlds You can perform these actions by opening a ter minal and typing mkdir p my_ros worlds mkdir p my_ros controllers joystick S cp SWEBOTS_MODULES_PATH projects languages ros worlds joystick wbt my_ros worlds hands on Copy the file WEBOTS_MODULES_PATH projects languages ros controllers joystick joy launch into my_ros controllers joystick cp SWEBOTS_MODULES_PATH projects languages ros controllers joystick joy launch my_ros controllers joystick We will use catkin the official ROS build system see ROS tutorials for catkin basics Create and init a catkin workspace You can perform these actions through a terminal by typing cd my_ros controllers joystick mkdir p catkin_ws src hands on S cd catkin_ws src S catkin_init_workspace Install the joy package sudo apt get install ros groovy joystick drivers S rosdep install joy hands on 7 8 TUTORIAL 7 USING ROS 231 Create a ROS package named webots_joystick specifying dependency on roscpp and joy cd my_ros controllers joystick catkin_ws src hands on S catkin_create_pkg webots_joystick roscpp joy Calling catkin_create_pkg must have created the directory webot s_ joystick with the subdirectories webots_joystick src and webots_joystick include plus two files webots_joystick CMakeLists txt and webots_joystick package xml T
242. s png using the file selection di alog hands on The texture URLs must be defined either relative to the worlds directory of your project directory or relative to the default project directory WEBOTS_ MODULES_PATH projects default worlds In the default project directory you will find textures that are available for every world note Open the bricks jpng texture in an image viewer while you observe how it is mapped onto the Sphere node in Webots 0 note Textures are mapped onto Geometry nodes according to predefined UV map ping functions described in the Reference Manual A UV mapping function theory maps a 2D image representation to a 3D model 210 CHAPTER 7 TUTORIALS webots_projects tutorials worlds appearance wbt Webots PRO 7 4 1 Simulation View o 0 RECO BO ib p W W 0 00 00 000 ooox gt DirectionalLight gt Floor gt EPuck v DEF BALL Solid translation 0 063367 0 1 0 248686 rotation0 100 scale111 y children Y O Shape v O appearance Appearance 9 material NULL v texture ImageTexture v url textures bricks png E repeats TRUE E repeatT TRUE E filtering TRUE 9 textureTransform NULL nama Meli url String 1 O O textures bricks png Select Figure 7 8 Simulation after having setup the Light and the Appearance nodes 7 4 5 Rendering Options Webots offers several rendering modes available in the View menu V
243. s possible to add a force to the robot CTRL ALT left clicking drag the simulation as fast as possible In order to obtain a real time simulation note speed the Real Time button has to be pressed O Starting the simulation by pressing the Run button will make Webots running Now we are going to modify the world and decrease the step of the physics simulation this will increase the accuracy of the simulation In the scene tree view expand the WorldInfo node the first node Set its basicTimeStep field to 16 Then save the simulation hands on Just after you added the E puck node a black window appeared in the upper left corner of the 3D view It shows the content of Camera nodes but it will stay black until not explicitly used during a simulation In order to hide it you simply have to set the pixe1Size equal to 0 Then if you want to re enable them you have to set this field value to a positive number Detailed definitions can be found in chapter 3 of the Reference Manual In this tutorial we will not use the Camera devices of the E puck So we can hide the window by expanding the E puck node and setting the fields cam era_pixelSize to 0 Don t forget to revert the simulation before changing hands y ee the values and to save it after the modifications http www cyberbotics com reference 7 2 TUTORIAL 1 YOUR FIRST SIMULATION IN WEBOTS 20 MINUTES 199
244. same project if they share some content robots source code 3D shapes etc S theory In Webots open the wizard by selecting the Wizards gt New Project Directory menu item From this wizard follow the instructions to create a new project named tutorials in the my_webots_projects directory created be fore hands on From your desktop open the project directory and observe its subdirectories We will soon explain the purpose of each directory note 7 1 5 The Webots Graphical User Interface GUI The Webots main window is shown in figure 7 1 Make sure you understand well how the Webots main window is divided into subwindows before continuing A more detailed description of the Webots GUI is provided in section 2 3 7 2 Tutorial 1 Your first Simulation in Webots 20 minutes In this first tutorial you will create your first simulation This simulation will contain a simple environment a light and an arena with floor and walls a predefined robot e puck and a con troller program that will make the robot move see figure 7 2 The objective of this tutorial is to familiarize yourself with the user interface and with the basic concepts of Webots 194 CHAPTER 7 TUTORIALS rojects tutoria my_First_simulation wbt Webots PRO 7 4 1 File Edit View Simul Too Simulation View OE Text Editor a 8800 80 Ib p WW 0 00 00 000 ooox E DeEB8B0 AX 43 gt Worldinfo RectangleAre
245. see that the problem is caused by a NULL 0x0 time string argument passed to the sprintf function The next steps are to fix the problem recompile the controller and revert the simulation to give it another try Once it works correctly you can remove the g flag from the Makefile 5 6 Using Visual C with Webots 5 6 1 Introduction Microsoft Visual C is an integrated development environment IDE for C C available on the Windows platform On Windows Visual C is a possible alternative to using Webots built in gcc MinGW compiler Visual C can be used to develop controllers using Webots C or C API The developer must choose one of these two APIs as they cannot be used together in controller code The C API is composed of h files that contains flat C functions that can be used in C or C controllers The C API is composed of hpp files that contain C classes and methods that can be used in C controllers only Two Visual C projects examples are included in Webots distribution WEBOTS_MODULES _ PATH projects robots khr 2hv controllers khr2 khr2 vcprojandWEBOTS_ MODULES_PATH projects robots khr 2hv plugins physics khr2 physics vcpro j However in principle any C or C controller from Webots distribution can be turned into a Visual C project 5 6 USING VISUAL C WITH WEBOTS 149 5 6 2 Configuration When creating a Webots controller with Visual C it is necessary to specify the path to Webots h and or
246. sers with a one button mouse should hold down the Control key Ctrl to emulate the right mouse button This way your are drawing a 3D vector with origin the center of mass and whose end is located in the plane parallel to the view which passes through this center The object is prompted to turn around the vector direction the intensity of the applied torque being directly proportional to the product of the mass by the length of the 3D vector In pause mode you can simultaneously add a force and a torque to the same selected solid Camera rotation can be useful when checking wether your note force torque vector has the desired direction 2 4 6 Moving and resizing Overlays By default for each Camera and Display device an overlay showing the recorded or displayed image is visible in the 3D view The device type is indicated by the border color magenta for Camera devices and cyan for Display devices see figure 2 5 This overlay can be moved to the desired position on the view by clicking on it and dragging the mouse In order to resize the overlay the user has to click on the icon located at the bottom right corner and drag the mouse during this action the original not scaled image size will be indicated using darker areas as depicted in figure 2 6 Additionally a close button is available on the top right corner to hide the overlay Once the robot is selected it is also possible to show or hide the overlay images from the Camera Device
247. sform to lt none gt Export 3D tools show resize handles Figure 2 9 Webots node editor Additionally when a node is selected other actions are available as shown in figure 2 9 Tranform to Allow to change the type of the selected node by chosing the target type from a given list of suitable types This action is not available for all node s types Export Exports nodes that can then be imported in other worlds Source Displayed only when a PROTO node is selected opens the corresponding PROTO defi nition file in the text editor Result Displayed only when a procedural PROTO node is selected opens the PROTO definition file generated by the template engine in the text editor Show resize handles Displays the handles for resizing and scaling the selected node from the 3D Window This option is disabled for PROTO nodes and only displayed for Geometry nodes and nodes derived from Transform We recommend to use the Scene Tree to write Webots world files However because the nodes and fields are stored in a human readable form it is also possible to edit world files with a regular text editor Some search and replace note operations may actually be easier that way Please refer to Webots Reference Manual for more info on the available nodes and the world file format 2 6 Preferences The Webots preferences can be modified by a dialog box which can be open from the Webots gt Preferences menu item on Mac
248. sion detection mechanism is based on the shapes specified in the boundingObjects Now if you want to programmatically detect collision there are several methods 1 In controller code you can detect collision by using TouchSensors placed around your robot body or where the collision is expected You can use TouchSensors of type bumper that return a boolean status 1 or O whether there is a collision or not In fact a bumper TouchSensor will return 1 when its boundingOb ject intersects another boundingObject and 0 otherwise 2 In supervisor code Webots PRO required you can detect collisions by tracking the po sition of robots using the wo_supervisor_field_get_ functions Here is a naive example assuming that the robots are cylindrical and moving in the xz plane define ROBOT_RADIUS int are_colliding WbFieldRef transl WbFieldRef trans2 const double pl wb_supervisor_field_get_sf_vec3f transl const double p2 wb_supervisor_field_get_sf_vec3f trans2 double dx p2 0 p1 0 double dz p2 2 p1 2 double dz p2 2 p1 2 return sqrt dx dx dz dz lt 2 0 ROBOT_RADIUS do this once only in the initialization WoNodeRef robotl wb_supervisor_node_get_from_def MY_ROBOT1 WoNodeRef robot2 wb_supervisor_node_get_from_def MY_ROBOT2 i WbFieldRef transl wbh_supervisor_node_get_field robotl translation
249. so make the simulation slower so a tradeoff has to be found Note that the value of the control step wb_robot step TIME STEP may have to be adapted to avoid warnings 2 Reduce the value of the JointParameters springConstant and JointParam eters dampingConstant fields or avoid using springs and dampers at all 3 Avoid large mass ratios A Joint that connects a large and a small mass Physics mass together will have a hard time to keep its error low For example using a Joint to connect a hand and a hair may be unstable if the hand hair mass ratio is large Mnttp ode wiki org wiki index php title Manual 270 CHAPTER 9 WEBOTS FAQ 4 Increase the value of Wor1dInfo CFM This will make the system more numerically robust and less susceptible to stability problems This will also make the system look more spongy so a tradeoff has to be found 5 Avoid making robots or other objects move faster than reasonably for the time step WorldInfo basicTimeStep Since contact forces are computed and applied only at every time step too fast moving bodies can penetrate each other in unrealistic ways 6 Avoid building mechanical loops by using Connector nodes The mechanical loops may cause constraints to fight each other and generate strange forces in the system that can swamp the normal forces For example an affected body might fly around as though it has life on its own with complete disregard for gravity 9 3 2 How to m
250. st solution and the easiest one is to use the standard ROS controller It is part of the Webots default controllers and is available in any project This controller can be used on any robot in Webots and acts as a ROS node providing all the Webots functions as services or topics to other ROS nodes The second custom and more complicated solution is to build your own Webots controller that will also be a ROS node using Webots and ROS libraries This solution should only be used for specific application that cannot be done with the standard controller Standard Controller This controller uses the 1ibCppCont roller library and proposes the available Webots func tionalities on the ROS network according to the robot s configuration Using the roscpp library 1t provides these Webots functions mostly as ROS services and uses standard messages type to avoid dependencies on third party packages During simulation there can be multiple instances of robots or devices and other Webots appli cations connected to the ROS network Therefore the controller uses a specific syntax to declare its services or topics on the network robot_unique_name device_name service topic_name robot_unique_name in order to avoid any misunderstanding between different instances of the same robot the name of the robot is followed by the ID of the process and the IP address of the computer device_name since the same function can refer to different device
251. sult of this operation is not visible yet Now we would like to add some environment a floor and some walls A predefined high level node called RectangleArena is designed to do this task quickly Select the last node of the scene tree view DirectionalLight Click on the Add button In the open dialog box choose PROTO Webots gt objects gt floors gt RectangleArena The new node has been hands on added and is appearing far away Use the left click and the wheel of the mouse in the 3D view to choose a better viewpoint It s a good time to improve the scene light Modify the following fields of the DirectionalLight node ambi entIntensity to l direction to 0 33 1 0 5 and castShadows hands on to TRUE In the scene tree the fields are displayed in blue if they differ from their default values note Now your environment should look like the one depicted in the figure 7 1 Save the new world into your project by selecting the File gt Save World As menu item Using the dialog box save the world into the my_webots_projects tutorials worlds my_first_ simulation wbt file location hands on Revert the simulation by selecting the File gt Revert World menu item hands on You can change the viewpoint of the 3D view by using the mouse buttons left button right button and the wheel note 7 2
252. t files in VRML 1 0 format Once imported these objects appear as Group Transform or Shape nodes at the bottom of the scene tree You can then either turn these objects into Webots nodes like Solid DifferentialWheels etc or cut and paste them into the children list of existing Webots nodes The Export VRML 2 0 item allows you to save the currently loaded world as a wrl file conforming to the VRML97 standard Such a file can in turn be opened with any VRML97 viewer and most 3D modeling software o The Take Screenshot item allows you to take a screenshot of the current view in Webots It opens a file dialog to save the current view as a PNG or JPG image 2 3 THE USER INTERFACE 41 HE The Make Movie item allows you to create MPEG movies Linux and Mac OS X or AVI movies Windows Once the movie recording is started this item is changed in Stop Movie During the recording it is possible to the change the running mode and pause the simulation However frames are only captured during Webots steps and not when the simulation is paused The Export HTML5 Model item allows you to export the current world as an interactive 3D html file using the X3DOM web standard based on WebGL This is especially useful for publishing Webots created worlds on the Web X3DOM is supported in recent versions of Fire fox Chrome Internet Explorer and Safari on Mac OS X see details on the X3DOM web site With the Chrome browse
253. t math h gt 4 5 define TIME_STEP 32 6 7 int main 8 wb_robot_init 9 10 WbDeviceTag motor wb_robot_get_device my_motor 11 12 double F 2 0 frequency 2 Hz 13 double t 0 0 elapsed simulation time 14 15 while 1 16 double pos sin t 2 0 MPI x F lg wb_motor_set_position motor pos 18 wb_robot_step TIME_STEP 19 t double TIME_STEP 1000 0 20 21 22 return 0 23 When wb_robot_step returns the motor has moved by a certain linear or rotational amount which depends on the target position the duration of the control step specified with wb_robot_step the velocity acceleration force and other parameters specified in the wbt description of the Motor For example if a very small control step or a low motor veloc ity is specified the motor will not have moved much when wb_robot_step returns In this case several control steps are required for the Rotat ionalMotor to reach the target position If a longer duration or a higher velocity is specified then the motor may have fully completed the motion when wb_robot_step returns Note that wo motor_set position only specifies the desired target position Just like with real robots it is possible in physics based simulations only that the RotationalMot ro is not able to reach this position because it is blocked by obstacles or because the motor s torque maxForce is insufficient to oppose to the gra
254. t menu item Note that the Follow Object state is saved in the wbt file 3http www x3dom org 42 CHAPTER 2 GETTING STARTED WITH WEBOTS The Restore Viewpoint item restores the viewpoint s position and orientation to their initial set tings when the file was loaded or reverted This feature is handy when you get lost while navi gating in the scene and want to return to the original viewpoint The Fullscreen item enables and disables displaying the 3D window on the entire screen The Projection radio button group allows to choose between the Perspective Projection default and the Orthographic Projection mode for Webots simulation window The perspective mode corresponds to a natural projection in which the farther an object is from the viewer the smaller it appears in the image With the orthographic projection the distance from the viewer does not affect how large an object appears Furthermore with the orthographic mode lines which are parallel in the model are drawn parallel on the screen therefore this projection is sometimes useful during the modelling phase No shadows are rendered in the orthographic mode The Rendering radio button group allows to choose between the Plain Rendering default and the Wireframe modes for Webots simulation window In plain rendering mode the objects are rendered with their geometrical faces materials colors and textures in the same way they are usually seen by an eye or a camera In wire
255. t setting the 3D rendering abilities The initial param eters of these settings may vary from one computer to another depending on the GPU OpenGL abilities e The RTT preferred mode option allows you to modify the method used to create the Camera device images The methods are sorted from the most efficient one to the less efficient one e The Disable shadows option allows you to disable completely the shadows in the 3D view and in the Camera rendering whatever the values of the Light castShadows fields The global performances can be improved by disabling this feature but on the other hand the rendering is more difficult to understand and less pretty e The Disable shader option allows you to use the regular OpenGL shading model instead of a custom shading This custom shading model computes the light effects on the 3D objects per pixel instead of per vertex resulting in a much smoother rendering It may be interesting to disbale this feature on old GPU if the shaders are not well supported 56 CHAPTER 2 GETTING STARTED WITH WEBOTS e The Disable camera anti aliasing option allows you to bypass all the Camera antialiasing fields and to disable this feature We observed that some hardware doesn t support the OpenGL feature about anti aliasing when rendering into a texture RTT 2 7 Citing Webots If you write a scientific paper or describe your project involving Webots on a web page we will greatly appreciate if you can add a refere
256. tarted from Webots On Windows the MATLAB installer will normally add MATLAB s bin directories to your Path environment variable so usually Webots will be able to locate MATLAB after a standard installation However in case it does not work please make sure that your Path contains this directory or something slightly different according to your MATLAB version Path C Program Files MATLAB R2009b bin On Linux the MATLAB installer does normally suggest to add a symlink to the mat lab startup script in the usr local bin directory This is a good option to make mat lab glob ally accessible Otherwise you can create the link at anytime afterwards with this shell command please change according to your actual MATLAB installation directory and version sudo ln s usr local MATLAB R2014a bin matlab usr local bin matlab Similarly on Mac OS X if Webots is unable to find the mat lab startup script then you should add a symlink in usr bin sudo ln s Applications MATLAB_R2014a app bin matlab usr bin matlab 4 7 4 Display information to Webots console On Linux and Mac OS X the Matlab output is redirected as is to the Webots console This means you can use all the Matlab display features disp display omitting the semicolon character at the end of a statement etc On Windows the Matlab output is not redirected to the Webots console The wob_console print text stream function should be used t
257. tarted on a remote computer by using ssh or a similar command However Webots will work only if it can get a X11 connection to a X server running locally on the same computer It is currently not possible to redirect Webots graphical output to another computer 5 7 1 Using the ssh command Here is the usual way to start from computer A a Webots instance that will run on computer B ssh myname computerB org export DISPLAY 0 0 webots mode fast stdout stderr myworld wbt The first line logs onto computer B The 2nd line sets the DISPLAY variable to the display 0 and screen 0 of computer B This will indicate to all X11 applications including Webots that they needs to connect to the X server running on the local computer computer B in this case This step is necessary because the DISPLAY variable is usually not set in an ssh session The last line starts Webots the mode fast option enables the Fast simulation mode which is available only with Webots PRO The mode fast option makes the simulation run as fast as possible without graphical rendering which is fine because the graphical output won t be visible anyway from computer A Options stdout and stderr are used to redirect Webots output to the standard streams instead of Webots console otherwise the output would not be visible on computer A At this point Webots will start only if a X server with proper authorizations is running on com puter B To e
258. te Webots may work but is not officially supported on earlier versions of Mac OS X Since version 6 3 0 Webots is compiled exclusively for Intel Macs it does not run on old PowerPC Macs To use Webots on a PowerPC Mac you need Webots 6 2 4 or earlier these older versions were compiled as Universal Binary Other versions of Webots for other UNIX systems Solaris Linux PPC Irix may be available upon request 1 3 Verifying your graphics driver installation 1 3 1 Supported graphics cards Webots officially supports only recent nVidia and ATI graphics adapters So it is recommended to run Webots on computers equipped with such graphics adapters and up to date drivers provided by the card manufacturer 1 e nVidia or ATI Such drivers are often bundled with the operating system Windows Linux and Mac OS X but in some case it may be necessary to fetch it from the web site of the card manufacturer 1 3 2 Unsupported graphics cards Webots may nevertheless work with other graphics adapters in particular the Intel graphics adapters However this is unsupported and may work or not without any guarantee Some 22 CHAPTER 1 INSTALLING WEBOTS users reported success with some Intel graphics cards after installing the latest version of the driver Graphics drivers from Intel may be obtained from the Intel download center web site Linux graphics drivers from Intel may be obtained from the Intel Linux Graphics web site If some graphic
259. tem is a framework for robot software development providing op erating system like functionality on top of a heterogenous computer cluster ROS was originally developed in 2007 by the Stanford Artificial Intelligence Laboratory As of 2008 development continues primarily at Willow Garage ROS provides standard operating system services such as hardware abstraction low level device control implementation of commonly used functionality message passing between processes and package management It is based on a graph architecture where processing takes place in nodes that may receive post and multiplex sensor control state planning actuator and other messages The library is geared towards a Unix like system and is supported under Linux ex perimental on Mac OS X and has partial functionality under Windows ROS has two basic sides The operating system side ros as described above and ros pkg a suite of user contributed packages organized into sets called stacks that implement functionality such as simultaneous localization and mapping planning perception simulation etc http www ros org http www willowgarage com 4 8 USING ROS 135 ROS is released under the terms of the BSD license and is open source software It is free for commercial and research use The ros pkg contributed packages are licensed under a variety of open source licenses 4 8 2 ROS for Webots There are two ways to use ROS with Webots The fir
260. tep 0 267 92 9 How can I detect collisions cis 88 oe Re YR EER EE RS 268 9 2 10 Why does my camera window stay black 269 9 3 Modelling cia em a RR AAA BLE GRR A AE 269 9 3 1 My robot simulation explodes what should I do 269 9 3 2 How to make replicable deterministic simulations 270 9 3 3 How to remove the noise from the simulation 271 9 3 4 How can I create a passive joint ces Se be She RES EEE HES 271 9 3 5 Is it possible fix immobilize one part of a robot 271 9 3 6 Should I specify the mass or the density in the Physics nodes 272 9 3 7 How to get arealisitc and efficient rendering 2 44 44 4484 244 272 SA ASUSTADOS 24 62 ek tk a ee ee Ge a ERS 273 9 4 1 Why is Webots slow on my computer o 273 9 4 2 How can I change the speed of the simulation 273 10 Known Bugs 275 RUT General DUSS lt a ESS RRA A Re RATA E 215 ETA tel GNA STARS CANES osos oe dou Se OSE SS A 213 10 1 2 Virmalization s cours ess ER a a SR a ai HES 275 10 1 3 Collision AM 275 10 1 4 Orientation dependent friction lt lt lt soc ecs Gee S46 a wees 276 10 2 MacOSX e 3 kek bee e ES EGR RASS RARA 276 10 2 1 Matlab and robot plugins o 22222228222 nai 276 ES LL e a o pe ao e Re ee rd Ge Ss ee S 276 10 3 1 Window refreshi ie e ao o ace oma a oh a BD HH HH S 276 O32 SS Se oea o a ed eed ana ee ee aoe Bae a
261. tered on Cy berbotics web site will receive an invitation e mail explaining how to register a Webots account and use the newly granted Webots licenses For existing accounts no e mail is sent and it is your responsibility to inform the students about their modified license rights Phttps www cyberbotics com 1 6 CLASSROOM LICENSE SETUP 31 1 6 2 Classrom Setup You can install Webots on all the computers in a classroom even if you have more computers than licenses In our example if you have 20 licenses and 30 computers then 20 students could use the software simultaneously on any of the 30 computers If a 21rst student comes in he won t be able to start Webots until one of the 20 students stops using Webots Restrict the license to specific machines It is possible to restrict the use of your licenses to a specific classroom or more generally to a number of specific computers This can be achieved from the Module pack section of the administration web page click on the license you want to restrict and a new page entitled Edit module pack should be displayed On this page set an IP range value to limit the use of this pack to machines with a specific IP address For example 128 179 67 143 128 179 67 146 123 179 67 145 will limit the use of Webots to these 3 IP addresses It is also possible to use an IP mask CIDR notation to specify a range of IP addresses For example 128 179 67 143 24 128 178 12 12
262. the set of data to be reset it is sometimes difficult to reset everything Neither motor positions nor the robot controller s are reset this way The motor po sitions should be reset using the wo_motor_set_position and the robot controller should be reset by sending a message from the supervisor process to the robot controller process using 174 CHAPTER 6 PROGRAMMING FUNDAMENTALS Webots Emitter Receiver communication system The robot controller program should be able to handle such a message and reset its state accordingly Using the wb_supervisor_simulation_revert function This function restarts the physics simulation and all controllers from the very beginning With this method everything is reset including the physics and the motor positions and the controllers But this function does also restart the controller that called wo_supervisor_simulation_ revert this is usually the controller that runs the optimization algorithm and as a conse quence the optimization state is lost Hence for using this technique it is necessary to develop functions that can save and restore the complete state of the optimization algorithm The op timization state should be saved before calling wo_supervisor_simulation_revert and reloaded when the Supervisor controller restarts Here is a pseudo code example 1 finclude lt webots robot h gt 2 include lt webots supervisor h gt 3 4 void run_robot const double param
263. ther with the Choregraphe program of Aldebaran Robotics Currently Webots supports the Nao v3 3 v4 0 and v5 0 versions with and without their articulated fingers respectively with 25 and 21 degrees of freedom for the first two The Webots installation includes several world files with Nao robots You will find some in this folder WEBOTS_MODULES_PATH projects robots aldebaran worlds The nao wbt and nao_indoors wbt are meant to be used with Choregraphe see below The nao_demo wbt is a demonstration of a very simple controller that uses Webots C API instead of Choregraphe The nao_mat lab wbt world is an example of programming Webots using the Matlab API The nao_robocup wbt world is an example of how to use the NAOqi API inside Webots It is the same API that is used in Choregraphe meaning that you can program Nao inside Webots without using Choregraphe 1f you want to In this world Nao tries to shoot the ball in the goal You can find another NAOqi example in the WEBOTS_MODULES_PATH projects contests nao_challenge 2013 2014 worlds folder The challenge wbt file in this folder is a solution to the NAO Challenge contest edition 2013 2014 In addition Nao robots are also used in the world files of the Robotstadium contest These files are located in this folder WEBOTS_MODULES_PATH projects contests robotstadium worlds 8 2 2 Using Webots with Choregraphe These instructions have been tested with Webots 8 0 0 and Choregraph
264. tial_wheels_ set_speed function to send a specific command to the real robot with the wheel speeds as an argument This command can be sent to the real robot via the serial port of the PC or any other PC robot interface you have You will probably need to make some unit conversions since your robot may not use the same units of measurement as the ones used in Webots The same applies for reading sensor values from the real robot Developing a remote control plugin Webots already provides some facilities to implement a remote control library and in particular it is possible to develop it as a controller plugin Once set in the corresponding field of the Robot node this remote control plugin will be executed automatically when running the controller Implementation details are described in subsection 6 6 5 Special functions The wb_robot_init function must be the first called function It performs the controller library s initialization The wb_robot_step function should be called repeatedly typically in an infinite loop It requests that the simulator performs a simulation step of ms milliseconds that is to advance the simulation by this amount of time The wb_robot_cleanup function should be called at the end of a program in order to leave the controller cleanly Running your real robot Once linked with your own remote control plugin you can control your real robot by running the simulation in Webots It might be
265. tion If a Java controller fails to execute or compile check that the java respectively the javac commands are reachable You can verify this easily by opening a Terminal Linux and Mac OS X or a Command Prompt Windows and typing java or javac If these commands are not reachable from the Terminal or Command Prompt they will not be reachable by Webots In this case check that the JDK is installed and that your PATH variable is defined correctly as explained above If you run into an error message that looks approximately like this Native code library failed to load See the chapter on Dynamic Linking Problems in the SWIG Java documentation for help java lang UnsatisfiedLinkError libJavaController jnilib no suitable image found this is due to a 32 bit 64 bit incompatibility between Java Virtual Machine JVM and Webots On Mac OS X this problem should disappear after you upgrade to a recent version of Webots 6 3 0 or newer On Windows Webots is only compatible with 64 bit versions of Java On Linux and Mac OS X you should be able to solve this problem by replacing the default java command string by java d32 or java d64 in the dialog Tools gt Preferences gt General gt Java command 4 5 3 Link with external jar files When a Java controller is either compiled or executed respectively the java and the javac commands are executed with the classpath option This option is filled internally with the location
266. tion must be based on the OpenGL API hence some OpenGL knowledge will be useful You will find an sample implementation in the Reference Manual in the chapter about the Physics Plugin 9 2 8 What does this mean The time step used by controller is not a multiple of World Info basicTimeStep Webots allows to specify the control step and the simulation step independently The con trol step is the argument passed to the wb_robot_step function it specifies the dura tion of a step of control of the robot The simulation step is the value specified in World Info basicTimeStep field it specifies the duration of a step of integration of the physics simulation in other words how often the objects motion must be recomputed The execution of a simulation step is an atomic operation it cannot be interrupted Hence a sensor measurement or a motor actuation must take place between two simulation steps For that reason the control step specified with each wb_robot_step must be a multiple of the simulation step If it is not the case you get this error message So for example if the WorldInfo basicTimeStep is 16 ms then the control step argument passed to wob_robot_step can be 16 32 48 64 80 128 1024 etc nttp ode wiki org wiki index php title Manual 268 CHAPTER 9 WEBOTS FAQ 9 2 9 How can I detect collisions Webots does automatically detect collisions and apply the contact forces whenever necessary The colli
267. tion my_leg 0 56 3 wbh_robot_step 40 6 1 CONTROLLER PROGRAMMING Similarly this code does not make much sense either 161 while 1 double dl wb_distance_sensor_get_value ds1 j double d2 wb_distance_sensor_get_value ds1 if d2 lt dl WRONG d2 will always equal dl here avoidCollision wb_robot_step 40 NNN FWN a since there was no call to wo_robot_step between the two sensor readings the values returned by the sensor cannot have changed in the meantime A working version would look like this 1 while 1 2 double dl wb_distance_sensor_get_value ds1 3 wb_robot_step 40 4 double d2 wb_distance_sensor_get_value dsl 5 if d2 lt dl 6 avoidCollision 7 wb_robot_step 40 8 However the generally recommended approach is to have a single wo_robot_step call in the main control loop and to use it to update all the sensors and actuators simultaneously like this l while 1 2 readSensors 3 actuateMotors 4 wb_robot_step TIME_STEP a Note that it may also be judicious to move wb_robot_step to the beginning of the lo order to make sure that the sensors already have valid values prior to entering the read Op in Sen sors function Otherwise the sensors will have undefined values during the first iteration of the loop hence while 1 wb_robot_step TIME_S
268. to draw on the floor The controller randomly chooses the ink color The ink on the floor fades slowly Use the Y and X keys to switch the Pen on and off 3 2 WEBOTS DEVICES 83 Figure 3 24 range_finder wbt 3 2 13 range finder wbt Keywords Range finder Camera DifferentialWheels In this example the robot uses a range finder Camera to avoid obstacles The range finder measures the distance to objects so the robot knows if there is enough room to move forward 84 CHAPTER 3 SAMPLE WEBOTS APPLICATIONS Figure 3 25 binocular wbt 3 3 How To This section gives various examples of complexe behaviours and or functionalities The world files are located in the WEBOTS_MODULES_PATH projects samples howto world directory and their controllers in the WEBOTS_MODULES_PATH projects samples howto controllers directory For each the world file and its corresponding controller are named according to the behaviour they exemplify 3 3 1 binocular wbt Keywords Stereovision Stereoscopy Camera This example simply shows how to equip a robot with two Cameras for stereovision The example does not actually perform stereovision or any form of computer vision 3 3 HOW TO 85 Figure 3 26 biped wbt 3 3 2 biped wbt Keywords Humanoid robot biped robot power off passive joint In this example a biped robot stands up while his head rotates After a few seconds all the motors are turned off an
269. ton and drag e Lift To raise or lower and object hold down the Shift key press both left and right mouse buttons or the middle button and drag Alternatively the mouse wheel combined with the Shift key can also be used If you are a Mac user with a single button mouse hold the Shift key and the Control key Ctrl down and press the mouse button to rotate the selected object according to mouse motion Hold the Shift key and the Command key note key with Apple symbol down and press the mouse button to lift the selected object according to mouse motion 2 4 4 Applying a force to a solid object with physics To apply a force to an object place the mouse pointer where the force will apply hold down the Alt key and left mouse button together while dragging the mouse Linux users should also 50 CHAPTER 2 GETTING STARTED WITH WEBOTS hold down the Control key Ctrl together with the Alt key This way your are drawing a 3D vector whose end is located in the plane parallel to the view which passes through the point of application The intensity of the applied force is directly proportional to the cube of the length of this vector 2 4 5 Applying a torque to a solid object with physics To apply a torque to an object place the mouse pointer on it hold down the Alt key and right mouse button together while dragging the mouse Linux users should also hold down the Control key Ctrl together with the Alt key Also Mac OS X u
270. translations may not always be complete or accurate As a user of Webots you are very welcome to help us fix these incomplete or inaccurate translations This is actually a very easy process which merely consists of editing a UTF 8 XML file and processing it with a small utility Your contribution is likely to be integrated into the upcoming releases of Webots and your name acknowledged in this user guide Even if your language doesn t appear in the current Webots Preferences panel under the General tab you can very easily add it To proceed with the creation of a new translation or the improve ment of an existing one please follow the instructions located in the readme txt file in the Webots resources translations folder Don t forget to send us your translation files Chapter 2 Getting Started with Webots This chapter gives an overview of Webots windows and menus 2 1 Introduction to Webots 2 1 1 What is Webots Webots is a professional mobile robot simulation software package It offers a rapid prototyp ing environment that allows the user to create 3D virtual worlds with physics properties such as mass joints friction coefficients etc The user can add simple passive objects or active ob jects called mobile robots These robots can have different locomotion schemes wheeled robots legged robots or flying robots Moreover they may be equipped with a number of sensor and actuator devices such as distance sensors drive
271. troller s programming language or platform This is done deliberately to ensure the platform and pro gramming language independence of wbt files So when Webots tries to start a controller it must first determine what programming language is used by this controller So Webots looks in the project s controllers directory for a subdi rectory that matches the controller name Then in this controller directory it looks for a file that matches the controller name For example if the controller name is xyz_controller then Webots 125 126 CHAPTER 4 LANGUAGE SETUP looks for these files in the specified order in the PROJECT_DIRECTORY controllers xyz_controller directory 1 xyz_controller exe a binary executable 2 xyz_controller class a Java bytecode class 3 xyz_controller jar a Java jar file 4 xyz_controller bsg a Webots BotStudio file 5 xyz_controller py a Python script 6 xyz_controller m a MATLAB script The first file that is found will be executed by Webots using the required language interpreter java python matlab So the priority is defined by the file extension e g it won t be possible to execute xyz_controller mifa file named xyz_controller py is also present in the same controller directory In the case that none of the above filenames exist or if the required language interpreter is not found an error message will be issued and Webots will start the void controller instead
272. trollers simple_controller controllers simple_controller Makefile controllers simple_controller simple_controller c controllers simple_controller simple_controller exe The main executable name must be identical to the directory name note You can create all the files needed by a new controller using the wizard New Robot Controller described in chapter 2 note 5 3 Compiling Controllers in a Terminal It is possible to compile Webots controllers in a terminal instead of the built in editor In this case you need to define the WEBOTS_HOME environment variable and make it point to Webots installation directory The WEBOTS_HOME variable is used to locate Webots header files and libraries in the Makefiles Setting an environment variable depends on the platform and shell here are some examples 5 3 1 Mac OS X and Linux These examples assume that Webots is installed in the default directory On Linux type this 5 4 USING WEBOTS MAKEFILES 143 S export WEBOTS_HOME usr local webots or add this line to your bash_profile file On Mac OS X type this S export WEBOTS_HOME Applications Webots or add this line to your profile file Once WEBOTS_HOME is defined you should be able to compile in a terminal with the make command Like with the editor buttons it is possible to build the whole project or only a single binary file e g
273. u can use the wb_supervisor_node_get_position function Please check this function s description in the Reference Manual 2 To get the 3D position of any Transform or derived node placed at the root of the Scene Tree the nodes visible when the Scene Tree is completely collapsed you can use the wob_supervisor_field_get_sf_vec3f function Here is an example A simulation example that shows both the GPS and the Supervisor techniques is included in the Webots installation you just need to open this world WEBOTS_MODULES_PATH projects samples devices worlds gps wbt In physics plugin code In the physics plugin you can use ODE s dBodyGetPosition function Note that this function returns the position of the center of mass of the body this may be different from the center of the Solid Please find a description of ODE functions here 9 2 2 How can I get the linear angular speed velocity of a robot object Webots provides several functions to get the 3D position of a robot or an object see above by taking the first derivative of the position you can determine the velocity There are also some functions see below that can be used to get the velocity directly In controller code To get the angular velocity of a robot or robot part in the robot s controller code add a Gyro node to the robot or robot part then use wb_robot_get_device wb_gyro enable and wo_gyro_get_values functions You will find more i
274. ual name of the installed JDK package On Windows the PATH variable must be set using the Environment Variables dialog On Windows 7 and 8 this dialog can be opened like this Choose Start Settings Control Panel System and Security System and open Advanced system settings Select the Advanced tab and click on the Environment Variables button In the dialog in the User variables for section look for a variable named PATH Add the bin path of the installed SDK to the right end of PATH variables If the PATH variable does not exist you should create it A typical value for PATH is C Program Files Java jdk XXXXXXX bin Where jdk XXXXXX stands for the actual name of the installed JDK package Then you need to restart Webots so that the change is taken into account Note that the PATH can also be set globally for all users On Linux this can be achieved by adding it in the etc profile file On Windows this can be achieved by adding it to the Path variable in the System variables part of the Environment Variables dialog Linux and OpenJDK Instructions In alternative to Oracle JDK on most popular Linux distribution is also possible to directly install the open source JDK from the system package manager Detailed information can be found on the OpenJDK website Inttp www oracle com technetwork java javase downloads http openjdk java net install index html 130 CHAPTER 4 LANGUAGE SETUP Troubleshooting the Java installa
275. uctured like a VRML97 file It is composed of a list of nodes each containing fields Fields can contain values text strings numerical values or other nodes This section describes the user interface of the Scene Tree gives an overview of the VRML97 nodes and Webots nodes 2 5 1 Field Editor Nodes can be expanded with a double click When a field is selected its value can be edited at the bottom of the Scene Tree All changes will be immediately reflected in the 3D window The following buttons are available int the field editor section o Reset Resets a field to its default value 0 Help Context sensitive help for the currently selected node 2 5 THE SCENE TREE gt Worldinfo gt Viewpoint gt Y Background gt Y DirectionalLight gt DirectionalLight gt SoccerField gt Walls gt DEF YELLOW_GOAL Goal gt DEF BLUE_GOAL Goal gt DEF BALL Ball v Y DARwINOP translation 0 432867 0 341158 0 406412 controller soccer controllerArgs synchronization TRUE selfCollision FALSE name DARwIn OP plasticColor 0 301961 0 301961 0 301961 cameraWindowPosition 0 0 cameraPixelSize 1 cameraWidth 160 cameraHeight 120 waistBand FAL SF rotation Rotation O x 0 m y 1 tim z 0 m angle 1 29435 rad Figure 2 8 Scene Tree Window bd 53 54 CHAPTER 2 GETTING STARTED WITH WEBOTS Robot O Node Mass Position DEF STEWART_PLATFORM USE count 0 Tran
276. uilding other Webots ROS projects 7 9 GOING FURTHER 233 In case you need to configure your joystick please refer to the ROS joy tuto rials note 7 8 2 Conclusion You should be able to run the joystick you just built as the original one open my_ros worlds joystick wbt and hit the play button You hence achieved a fully functional Webots controller implemented as a ROS node Exploring further Webots C C and Python APIs will allow you to integrate larger ROS frameworks 7 9 Going Further You have now enough knowledge to set up your own simulation Webots You are able to design and implement a robot to setup its controller and to design an environment However the Webots possibilities go much beyond this Reading the documentation related with your application in the User Guide or in the Reference Manual is the first step to extend your knowledge The algorithmic to develop your controllers is not explained in the Webots documentation How ever another tutorial known as curriculum tackle some famous robot programming problems through a sequence of exercises using the e puck robot and the C language 3http www cyberbotics com guide 234 CHAPTER 7 TUTORIALS Chapter 8 Robots 8 1 Using the e puck robot In this section you will learn how to use Webots with the e puck robot figure 8 1 E puck is a miniature mobile robot originally developed at the EPFL for teaching purposes by th
277. utomatically terminate Webots when the job is over 5 8 Transfer to your own robot In mobile robot simulation it is often useful to transfer the results onto real mobile robots Webots was designed with this transfer capability in mind The simulation is as realistic as possible and the programming interface can be ported or interfaced to existing real robots Webots already comprises transfer systems for a number of existing robots including e puck DARwIn OP Khepera and Hemisson This section explains how to develop your own transfer system to your own mobile robot Since the simulation is only an approximation of the physics of the real robot some tuning is always necessary when developing a transfer mechanism for a real robot This tuning will affect the simulated model so that it better matches the behavior of the real robot 5 8 TRANSFER TO YOUR OWN ROBOT 153 5 8 1 Remote control Overview Often the easiest way to transfer your control program to a real robot is to develop a remote control system In this case your control program runs on the computer but instead of sending commands to and reading sensor data from the simulated robot it sends commands to and reads sensor data from the real robot Developing such a remote control system can be achieved in a very simple way by writing your own implementation of the Webots API functions as a small library For example you will probably have to implement the wo_differen
278. vity etc If you want to control the motion of several RotationalMotors simultaneously then you need to specify the desired position for each RotationalMotor separately using wb_mo tor_set_position Then you need to call wo_robot_step once to actuate all the RotationalMotors simultaneously 160 CHAPTER 6 PROGRAMMING FUNDAMENTALS 6 1 4 How to use wb_robot_step Webots uses two different time steps e The control step the argument of the wo_robot_step function e The simulation step specified in the Scene Tree WorldInfo basicTimeStep The control step is the duration of an iteration of the control loop It corresponds to the parameter passed to the wb_robot_step function The wb_robot_step function advances the controller time of the specified duration It also synchronizes the sensor and actuator data with the simulator according to the controller time Every controller needs to call wo_robot_step at regular intervals If a controller does not call wo_robot_step the sensors and actuators won t be updated and the simulator will block in synchronous mode only Because it needs to be called regularly wo_robot_step is usually placed in the main loop of the controller The simulation step is the value specified in WorldInfo basicTimeStep in milliseconds It indicates the duration of one step of simulation i e the time interval between two computations of the position speed collisions etc of every
279. wheels cameras motors touch sensors emit ters receivers etc Finally the user can program each robot individually to exhibit the desired behavior Webots contains a large number of robot models and controller program examples to help users get started Webots also contains a number of interfaces to real mobile robots so that once your simulated robot behaves as expected you can transfer its control program to a real robot like e puck DARwIn OP Nao etc Adding new interfaces is possible through the related sytem 2 1 2 What can I do with Webots Webots is well suited for research and educational projects related to mobile robotics Many mobile robotics projects have relied on Webots for years in the following areas e Mobile robot prototyping academic research the automotive industry aeronautics the vacuum cleaner industry the toy industry hobbyists etc 33 34 CHAPTER 2 GETTING STARTED WITH WEBOTS Robot locomotion research legged humanoids quadrupeds robots etc Multi agent research swarm intelligence collaborative mobile robots groups etc Adaptive behavior research genetic algorithm neural networks Al etc Teaching robotics robotics lectures C C Java Python programming lectures etc Robot contests e g www robotstadium org or www ratslife org 2 1 3 What do I need to know to use Webots You will need a minimal amount of technical knowledge to develop your own simulations e A basic
280. when off and red or green when on The motor speeds are displayed in blue and the motor position is displayed in the Encoder box in the bottom right hand corner of the window The camera image if present the ground sensor values if present and the accelerometer values are displayed in the corresponding boxes on the right side of the window This e puck control window appears because the robot Window field of the Dif ferential Wheel node in the world file was set to e puck_window Changing this robot Window to an empty string will disable this control window BotStudio BotStudio is a user interface for programming graphically the e puck thanks to a finite state automaton Behaviors such as wall follower collision avoider or line follower can be imple mented quickly thanks to this interface BotStudio is typically destinated for the education field particularly for beginners in robotics An automaton state of BotStudio corresponds to a state of the e puck actuators while a transition corresponds to a condition over its sensor values A transition is fired when all of its conditions are fulfilled logical AND A logical OR can be performed by several transitions between two states The actuators available in BotStudio are the LEDs and the motors Each automaton state have two sliders for setting the motor speed value Note that these values can be unset by clicking on the cursor of the slider Each state have also 10 square butt
281. wledge acquired in a tutorial is often required to continue with the next tutorial Therefore we strongly recommend you to respect their natural order Moreover we recommend you to ensure you understood all the concepts of a tutorial before proceeding further A Webots PRO license or a 30 days trial license is required to follow all the tutorials However an EDU license is sufficient to follow about 95 of this chapter as it won t allow you to program supervisor processes and physics plugins The last section will provide you with some hints to address problems that are not covered in this chapter The solutions of the tutorials are located into the WEBOTS_MODULES_PATH projects samples tutorials subdirectory of the Webots installation directory We hope you will enjoy your first steps with Webots Meanwhile we would really appreciate to receive your feedback regarding this chapter 191 192 CHAPTER 7 TUTORIALS 7 1 Prerequisites In this section you will learn how to setup your Webots environment It is obviously a necessary step to get started with the tutorials 7 1 1 Install Webots Webots has to be installed on your computer Install Webots by following the instructions given in chapter 1 hands on 7 1 2 Create a directory for all your Webots files The first step is to create a directory which will contain all your files related to Webots From your operating system interface choose a location on you
282. world file named joystick wbt and a controller named joystick which allows the user to drive a simulated robot using a joystick through the ROS joy node This controller is a very simple example of a ROS node running as a Webots controller It could be used as a starting point to develop more complex interfaces between Webots and ROS The controller directory includes all the Makefile machinery to call the build tools used by 4 9 INTERFACING WEBOTS TO THIRD PARTY SOFTWARE WITH TCP IP 137 ROS and Webots to produce the controller binary The ros folder also includes a README txt file with detailed installation and usage instructions Following the instructions README md is necessary to make the joystick example work on your Linux system In the Tutorials chapter you will find a section explaining how to rebuild note from scratch the Joystick example 4 9 Interfacing Webots to third party software with TCP IP 4 9 1 Overview Webots offers programming APIs for following languages C C Java Python and MATLAB It is also possible to interface Webots with other programming languages of software packages such as Lisp LabView etc Such an interface can be implemented through a TCP IP protocol that you can define yourself Webots comes with an example of interfacing a simu lated Khepera robot via TCP IP to any third party program able to read from and write to a TCP IP connection This example world is called kheper
283. y libraries and there is there fore best suited for installation on other Linux distributions These packages can be downloaded from our web site Some of the following commands requires the root privileges You can get these privileges by preceding all the commands by the sudo command note Webots will run much faster if you install an accelerated OpenGL drivers If you have a nVidia or ATI graphics card it is highly recommended that you install the Linux graphics drivers from these manufacturers to take the full note advantage of the OpenGL hardware acceleration with Webots Please find instructions here section 1 3 Webots needs the avconv program to create MPEG 4 movies that can be installed with libav tools and libavcodec extra 54 packages note Thttp www cyberbotics com linux 1 4 INSTALLATION PROCEDURE 23 Using Advanced Packaging Tool APT The advantage of this solution is that Webots will be updated with the system updates This installation requires the root privileges First of all you may want to configure your apt package manager by adding this line deb http www cyberbotics com debian binary 1386 or deb http www cyberbotics com debian binary amd64 in the etc apt sources list configuration file Then update the APT packages by using apt get update Optionally Webots can be autentified thanks to the Cyberbotics asc signature file which can be downloaded here
284. y occasionaly yield wrong contact points Sometimes the contact points may be slightly off the shape therefore causing unrealistic reaction forces to be applied to the objects Other times there are too few contact points therefore causing vibration or instabilities 10 1 4 Orientation dependent friction Although the friction model of ODE is very accurate the true friction cone is approximated by a linearized version which can introduce some orientation specific artifacts It is for example possible that an object slips more easily on another object in some direction than in some other even if the friction coefficients are set to be symmetric However in most of the cases it is possible to get rid of these effects by tuning correctly the friction parameters 10 2 MacOS X 10 2 1 Matlab and robot plugins The controllers and the robot plugins e g the robot windows are sharing the same process Generally this mechanism is working well but some instabilities crashes and warnings may occur when a robot uses a Matlab controller and a robot window at the same time This is due to some conflicts between the Qt libraries used by Matlab and the one used by Webots 10 3 Linux 10 3 1 Window refresh It may happen that the main window of Webots is not refreshed properly and appears blank at startup or upon resize or maximization This is caused by a conflict between the Compiz window manager and OpenGL Simply disabling Compiz should fix such a
285. yer 13296 pts 1 00 00 00 soccer_player 13297 pts 1 00 00 00 soccer_player 13298 pts 1 00 00 00 soccer_player 13299 pts 1 00 00 00 soccer_player 13300 pts 1 00 00 00 soccer_player 13301 pts 1 00 00 00 soccer_supervisor lt defunct gt On Mac OS X use rather ps x and on Windows use the Task Manager for this If one of your robot controllers is missing in the list or appearing as lt defunct gt this confirms that it has crashed and therefore blocked the simulation In this example the soccer_supervisor has crashed Note that the crash of a controller is almost certainly caused by an error in the controller code because an error in Webots would have caused Webots to crash Fortunately the GNU debugger gdb can usually help finding the reason of the crash The following example assumes that there is a problem with the soccer_supervisor controller and indicates how to proceed with the debugging 5 5 DEBUGGING C C CONTROLLERS 147 5 5 2 Using the GNU debugger with a controller The first step is to recompile the controller code with the g flag in order to add debugging information to the executable file This can be achieved by adding this line to the controller s Makefile CFLAGS g Then you must recompile the controller either by using the Clean and Build buttons of the Webots text editor or directly in a terminal S make clean make Note that the g flag should now appear in the compilation line Once you have recom

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