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ERRATIC Mobile Robot User Manual

1. 34 E 6 Controller command reference 35 E 7 Motor info packets 36 E 8 Configuration packet 37 E 9 Encoder packet 37 E 10 Analog packet 37 E 11 Sonar packet 38 Appendix F Power Port 39 Appendix G Erratic base dimensions 40 Figures and Tables Figure 2 1 Components for the Erratic robot 6 Figure 2 2 Top of the robot 6 Figure 2 3 Port side of the PC 7 Figure 2 4 Ports LED and power button on top of the robot 7 Figure 2 5 Inserting the first battery 8 Figure 2 6 Three batteries installed in the back of the robot 8 Figure 2 7 On off switch and
2. 14 3 8 Running standard Player clients 14 3 9 Running the Javaclient Viewer 15 3 10 Example client programs 16 4 Configuring the wireless interface 17 4 1 Configuration 17 4 2 Testing the wireless interface 17 4 3 Finding the robot on the network 17 4 4 Connecting to the robot 18 5 Robot Interfaces 19 5 1 Robot parameters and Player configuration file 19 5 2 Communication port 19 5 3 Robot type information 19 5 4 Player interface list 20 5 5 Position control 20 5 5 1 Odometry coordinate system
3. Analog and digital inputs are available through the low level packet interface A controller command turns the sending of the packets on or off The packet contains information about 4 analog channels and 3 digital channels The analog channels return a count of 0 1023 which translates to a voltage from 0V 3 5V The digital channels return a value of 0 1 which is mapped into a voltage of 0 or 1 The Player AioProxy class accesses either of these values Input Function Value Player proxy Analog Ch 0 Ch 1 Left motor current Right motor current 0 1023 25 mA cnt 25 mA cnt AioProxy GetCount ch or GetVoltage ch Analog Ch 2 Ch 3 User input User input 0 1023 AioProxy GetCount ch or GetVoltage ch Digital Ch 4 Ch 5 Left floor sensor Right floor sensor 0 1 0 floor 1 no floor AioProxy GetCount ch or GetVoltage ch ERA ROBOT USER S MANUAL 2009 VIDERE DESIGN 25 Input Function Value Player proxy Digital Ch 6 User input 0 1 AioProxy GetCount ch or GetVoltage ch 5 6 3 IR floor sensor Two IR floor sensors at the front of the robot detect drop offs such as a step down The sensors have a fixed sensing distance about 8 cm below the floor plane If they detect the floor they signal a lt 0 gt on digital channel 4 left or 5 right If they do not detect a floor they signal lt 1 gt The IR floor sensors are mapped by the Player driver to the IR
4. E 1 Communication channel Communication is through a USB 1 1 connection Host PC drivers convert the USB connection into a serial connection The name of the connection on Linux systems is dev erratic This device name is a symlink to dev ttyUSBn The symlink is performed automatically at boot up by rules in etc udev rules d 60 symlinks rules On MS Windows systems the connection is comX where X is the next highest serial port number The device communicates at a native speed of 38 4 Kbaud 8 bits per byte no parity 1 stop bit E 2 Special byte definitions Some bytes have a special meaning at certain points within a packet see subsequent sections These are given symbolic names as follows SYNC0 0xFA SYNC1 0xFB END 0xFE ARG 0x3B NARG 0x1B SARG 0x2B When integers are sent as arguments they are always inserted into the byte stream as 2 bytes The first byte is the low byte the second byte is the high byte of the integer E 3 Packet protocol The protocol is based on command packets that are sent to the controller and information packets that are received by the host PC All packets have the following format SYNC0 SYNC1 count count 2 bytes of data checksum 2 bytes E 4 Checksum calculation The checksum is calculated on the full packet starting after the SYNC bytes and includes the byte count The checksum algorithm is given here in C code The argument n is the number of byt
5. int 0 A 3 Motion parameters Motion parameters control the acceleration and velocity of the robot These parameters act on rotation and translation as independent controls For motion regimes where the velocity of each wheel is controlled independently the translational settings are used All these values can be changed with the configuration file when Player starts up Firmware Parameter Player driver config Default Effect pTransVelMax mm sec max_trans_vel m sec 1000 mm sec Maximum rotational velocity allowed pRotVelMax deg sec max_rot_vel deg sec 200 deg sec Maximum rotational velocity allowed pTransAcc mm sec2 trans_acc m sec2 400 mm sec2 Translation acceleration pTransDecel mm sec2 trans_decel m sec2 400 mm sec2 Translation deceleration pRotDecel deg sec2 rot_decel deg sec2 400 deg sec2 Rotation deceleration ERA ROBOT USER S MANUAL 2009 VIDERE DESIGN 29 Firmware Parameter Player driver config Default Effect pRotAcc deg sec2 rot_acc deg sec2 400 deg sec2 Rotation acceleration A 4 Motion control parameters These parameters affect the underlying PID control loop of the robot and the PWM pulse width modulation frequency and maximum duty cycle This loop runs at 200 Hz and provides fine motion servoing for velocity and position control of the wheels For testing purposes these parameters can be changed by Player using
6. 0 default direct_wheel_vel_control 0 Setting this option to 1 saves the settings in the robot making permanent whatever settings state it is in after settings of this config file are applied The settings can then be left out of other configuration files Note that some of the settings here are driver settings and not robot ones and are therefore not affected by a save save_settings_in_robot 0 ERA ROBOT USER S MANUAL 2009 VIDERE DESIGN 32 Appendix C Player server autostart The Player server can be autostarted at boot time on the robot The advantage to doing this is that there is no need to ssh in to the robot to start Player The disadvantage is that if there is a problem there is no way to tell what went wrong In this case it is always possible to start a shell on the robot and check if Player is running and if not to start it and see what the problem is There is a script installed in etc init d player that will turn on autostart of the Player server during boot This script has the Player command usr local bin player commented out To enable autostart uncomment this line ERA ROBOT USER S MANUAL 2009 VIDERE DESIGN 33 Appendix D Test program There is a standalone test program that exercises the robot controller via the low level packet interface The test program is a good way to check the functions of the robot and can be used as an example program for low level access via the pa
7. 2 8 Hokuyo URG installation 9 2 9 Hokuyo URG with tilt unit 9 2 10 STOC installation 10 2 11 STOC installation with pan tilt unit 10 3 Quick Start 12 3 1 Networking environment 12 3 2 Accessing the Onboard PC 12 3 2 1 Keyboard mouse and monitor 12 3 2 2 Wired Ethernet connection 12 3 2 3 Wireless access 13 3 3 Root access 13 3 4 Player software 13 3 5 PC Client software 13 3 6 Running the Player server 13 3 7 Services
8. Robot name parameters 28 A 2 Firmware version 28 A 3 Motion parameters 28 A 4 Motion control parameters 29 A 5 Saving parameters to flash 29 A 6 Parameter structure 29 Appendix B Player robot configuration file 31 Appendix C Player server autostart 32 Appendix D Test program 33 ERA ROBOT USER S MANUAL 2009 VIDERE DESIGN 3 Appendix E Erratic controller packet communications 34 E 1 Communication channel 34 E 2 Special byte definitions 34 E 3 Packet protocol 34 E 4 Checksum calculation 34 E 5 Command packets
9. USER S MANUAL 2009 VIDERE DESIGN 28 Appendix A Robot parameters Parameters for the robot change the behavior of the robot in various ways e g they set the maximum velocity for the robot Parameters are held permanently in flash memory on the embedded controller board of the robot When the robot is turned on these parameters are read into RAM on the controller where they take effect Parameters can be changed in RAM by issuing various packet commands Section E 6 The current parameters in RAM can be written to flash for permanent storage again by a packet command All the parameters can be read out by requesting a configuration packet via a controller command see Section 0 Some of the parameters are available from the Player interface via the configuration file Section 5 and Appendix B A 1 Robot name parameters The robot base has a set of parameters that define the robot s basic type These parameters can be set by the user but we recommend only changing the Name parameter to identify your robot There is a utility program for changing the name Parameter Type Default Value Name Null terminated string Erratic 1 Type Null terminated string Erratic Subtype Null terminated string Rev E Serial Null terminated string NNNN factory setting A 2 Firmware version The version of the controller code is held in flash memory Parameter Type Default Value Version int 1 Subversion
10. heading and translation velocity SetVelHead function With SetSpeed xvel yawvel a user program sets the desired velocities for translation and rotation lt xvel gt is in m sec lt yawvel gt is in rad sec Positive values for rotation velocity turn the robot counter clockwise negative clockwise Negative values for translation velocity move the robot backwards With SetVelHead xspeed yawangle a user program sets the desired velocity for translation and the desired heading relative to the odometry system For example if lt yawangle gt is specified as 85 degrees and the robot s odometry says that it is currently at 30 degrees then the robot will move 55 degrees counter clockwise and hold that heading 5 5 5 VEL2 mode The controller supports independent wheel control in which the velocities of each wheel are given There is a low level packet command for sending these velocities the controller automatically switches to VEL2 mode when it is received The Player driver support VEL2 mode with a configuration parameter Set to 1 to have the driver use individual wheel control direct_wheel_vel_control 0 If this parameter is set to 1 then all position2d commands are interpreted as individual wheel commands Note that it is not possible to switch between VEL2 and TR mode from within Player the mode is fixed when the driver starts In VEL2 mode the Player position2d proxy interprets SetSpeed commands as ref
11. interface User programs can access these values using the IrProxy class The values returned for members of this class are given in the table below The IR channel for the left sensors is 0 and the channel for the right is 1 IrProxy function Interpretation GetRange ch ch 0 left ch 1 right 0 1 m floor 1 0 m no floor GetVoltage ch ch 0 left ch 1 right 0V floor 1V no floor The placement of the IR floor sensors can be found with the GetPose ch function 5 7 Sonar sensors Erratic has an optional ring of 8 sonar sensors in the front of the robot The placement of these sensors is given below in Figure 5 2 The sonar sensors are MaxBotics EZ 1 sensors They are moderately sensitive able to detect objects out to 5 meters However it is recommended to only use readings that are less than 2 or 3 meters since the probability of false positives is very high for longer readings in typical indoor environments The acceptance angle for the sonars is well focused around 30 degrees with minimal side lobe response The technical specifications for the sonars are on the Videre website There is a low level packet interface to the sonar sensors Sending a sonar command will turn the sonars on or off When they are on the controller continuously sends sonar data packets Each packet contains one or more sonar range readings in mm indexed by the sonar number The data rate for the sonars is 20 Hz The Pla
12. odometry origin to 0 0 0 Encoder 19 ARG 1 turns on encoder packets 0 turns them off Analog 71 ARG 1 turns on analog info packets 0 turns them off Sonar 28 ARG 1 turns on sonar info packets 0 turns them off Servo 75 STRING Sets a servo motor position First byte is the servo number 0 2 second two bytes are the position as a 2 byte integer PWM freq 73 ARG Sets motor PWM frequency Values should be from 4000 to 16000 PWM duty 74 ARG Sets max PWM duty cycle in percent Trans PID P 80 ARG PID proportional parameter for translational motion Trans PID D 81 ARG PID differential parameter for translational motion Trans PID I 82 ARG PID integral parameter for Command Num Arg Effect translational motion Rot PID P 83 ARG PID proportional parameter for rotational motion Rot PID D 84 ARG PID differential parameter for rotational motion Rot PID I 85 ARG PID integral parameter for rotational motion Robot name 90 STRING Robot name max 20 chars Robot type 92 STRING Robot type max 20 chars Erratic Robot subtype 93 STRING Robot subtype max 20 chars Rev E Robot serial 91 STRING Robot serial number max 20 chars Save params 72 None Save current controller parameters to flash storage E 7 Motor info packets Motor packets are sent continuously from the controller at the rate of 20 Hz These packets are always sent
13. on one of the buttons on the left for example the Laser button Now the laser readings will appear in the Viewer graphics pane To move the robot press the Enable button to enable motor power Then click in the graphics pane and use the i j keys to increment or decrement the forward velocity and the j l keys to increment or decrement the rotational velocity As the robot moves you should see the sensors outline the shape of objects around the robot 3 10 Example client programs There are two simple client programs that show some interesting behavior of the robot These programs are found in the examples libplayerc directory of the distribution laserobstacleavoid This program moves the robot forward and turns if it encounters an obstacle ahead of the robot randomwalk This program is similar to the previous one but after a short interval it turns the robot in a new direction Figure 3 3 Javaclient Viewer program If the robot is tethered to a keyboard and monitor or to a wired Ethernet then be careful to only move the robot a small amount ERA ROBOT USER S MANUAL 2009 VIDERE DESIGN 17 4 Configuring the wireless interface The wireless interface is the best way to observe and control the robot Once the robot is connected over a wireless link you can connect to it from any PC on the network and run client programs to control the robot 4 1 Configuration To configure the wireless interface
14. power port inside the robot The other cable is a USB A to mini B cable The mini B end should be plugged into the USB port of the Hokuyo The other end should be plugged into one of the USB ports on the PC The Hokuyo URG is now ready to be used 2 9 Hokuyo URG with tilt unit The Hokuyo URG can come equipped with a tilt unit for tilting the rangefinder forward or backwards refer to Figure 2 8 The maximum amount of travel is 60 degrees forward and 90 degrees backward so that the URG can sweep the ceiling For shipping the cables are unplugged and the URG is removed from the top plate Remove the tape that holds the URG to the top plate and any other packing materials Using the four small nuts on the bottom of the URG install the Tilt unit to the matching holes on the top plate The miniature USB connector plugs into the USB slot of the URG and supplies communication to the device The black cable power connector plugs into Figure 2 7 On off switch and charger port on the left side of the robot Figure 2 8 Hokuyo URG mounted on a tilt unit Power switch Charger port ERA ROBOT USER S MANUAL 2009 VIDERE DESIGN 10 the 8 pin slot of the URG The tilt unit can be tested by turning on the power to the robot It should move to an upright position and stay there When the robot is turned off it is recommended to put the URG into the stowed position 90 degrees backwards In this position the URG is
15. the right of the caster wheel for inserting the batteries refer to Figure 2 5 The back plate of the robot can be removed with the two silver thumb screws on the rear sides of the robot Insert the first battery in the slot then slide it over all the way to the left until it Figure 2 3 Port side of the PC USB IEEE 1394 Ethernet video stereo and microphone ports Antenna is attached to the wifi connector Figure 2 4 Ports LED and power button on top of the robot Wifi antenna IEEE 1394 USB x2 Video Power Motor button LED ERA ROBOT USER S MANUAL 2009 VIDERE DESIGN 8 contacts a bumper Insert the second and third batteries in a similar manner You should now have three batteries in the robot Before proceeding ensure that the robot power switch is OFF Now connect the batteries to the internal power plugs of the robot There are three power plugs that are suspended from the underside of the robot top plate Connect one to each of the plugs on the batteries The plugs are polarized so they can only be connected in the correct way When you are finished the installed batteries should look like Figure 2 6 To test that they are working turn on the main power switch You should see the green LED light up on the motor switch Figure 2 2 Turn the main power switch OFF 2 6 Charging the batteries The batteries are charged before they are shipped but they should be re charged before
16. you must login to the onboard PC You must also have the following information from the systems administrator ESSID of the wireless network WEP key if WEP security is used If you are logged in using a keyboard and monitor you can use the Wireless administration tool to configure the wireless device Go to the menu at the top of the page and navigate to System gt Administration gt Networking You will then see a dialog with the Ethernet devices listed Choose the Wireless device and go to the Properties tab You can change the ESSID and WEP key there If you are logged in using SSH you must edit the file as root etc network interfaces Both emacs and vi editors are available In the interfaces file you will find the following lines for the wireless device USB wireless iface ath0 inet dhcp wireless essid MyNetwork wireless key MyKey wireless mode Managed auto rausb0 Change the ESSID and key to the appropriate values for your wireless network If there is no key then remove the wireless key line The wireless interface should now be configured for your network 4 2 Testing the wireless interface The wireless interface is configured to start automatically on boot You can check if it is enabled by using the ifconfig command This will list all of the currently enabled Ethernet interfaces If you need to start the wireless interface manually for instance to check if the configuration is working you can u
17. 21 5 5 2 Enabling the motors 21 5 5 3 Motor control modes 21 5 5 4 TR mode 21 5 5 5 VEL2 mode 22 5 5 6 Acceleration and velocity limits 22 5 5 7 Motor PWM and PID control 23 5 5 8 Saving settings 24 5 6 Analog and digital sensors 24 5 6 1 Battery voltage 24 5 6 2 Analog and digital inputs 24 5 6 3 IR floor sensor 25 5 7 Sonar sensors 25 5 8 Servo motors 26 6 Technical Support 27 Appendix A Robot parameters 28 A 1
18. B connector Optional IEE1394 connector ERA ROBOT USER S MANUAL 2009 VIDERE DESIGN 7 After removing blue tape connect the power and USB cables from the base to the PC See Figure 2 3 and Figure 2 4 for the connections Plug the 8 pin connector into the Erratic base and the USB cable into the lowest port on the PC 2 3 LED indicator The LED indicates the status of the robot When the robot is powered it is lit The color indicates the status of the robot controller Green when the controller is on but there is no power to the wheel motors Orange red green when the controller is on and there is power to the wheel motors Flashing when the battery is low lt 11V otherwise solid 2 4 Motor power button The red button is an emergency switch for stopping the motors when the robot is moving If you press this button and let it go power to the motors is cut off and the motors go limp This button can also be used to perform a basic motor controller test of the robot see Section 2 7 2 5 Installing the batteries Make sure that the main power switch Figure 2 7 is turned OFF before proceeding The robot is not shipped with the batteries installed The following description should be consulted when removing and re installing the batteries for the initial setup please read and follow carefully Batteries are installed from the back of the robot Locate the caster wheel in the back There is a slot to
19. ERA ROBOT USER S MANUAL 2009 VIDERE DESIGN 1 ERA Mobile Robot User s Manual Rev H October 2009 Player Software v 2 0 4 2009 Videre Design LLC ERA ROBOT USER S MANUAL 2009 VIDERE DESIGN 2 Table of Contents 1 Introduction 4 1 1 Base Characteristics 4 1 2 Onboard PC Characteristics 5 1 3 Warranty Information 5 2 Robot Setup 6 2 1 Components 6 2 2 Connecting the computer 6 2 3 LED indicator 7 2 4 Motor power button 7 2 5 Installing the batteries 7 2 6 Charging the batteries 8 2 7 Basic motor test 8
20. M 512 MB standard Optional up to 1 GB Storage 40 GB hard disk Optional up to 100 GB Ports 2x USB 2 0 1x IEEE 1394a FireWire 6 pin VGA DVI Removable drives CD ROM drive Wireless IEEE 801 11b g Power 30W maximum 20W normal use Weight 1 Kg 1 3 Warranty Information The ERA MOBI is sold with a one year warranty We check the robot s functionality thoroughly before shipping but due to the variability of shipping and end user conditions we cannot guarantee performance This warranty does not included damage from customer misuse mishandling or disassembly Examples of misuse can include but are not limited to damages sustained when disassembling the robot intentional modification of the robot or damages sustained during extreme use If you have any questions about the warranty do not hesitate to contact Videre Design sales videredesign com ERA ROBOT USER S MANUAL 2009 VIDERE DESIGN 6 2 Robot Setup The ERA comes with batteries and computer separate from the robot base for protection during shipping If the Hokuyo URG laser rangefinder or SICK laser rangefinder have been ordered then they are also un mounted from the robot base Sonar and IR floor sensors are already installed Please follow the directions in this section to set up your ERA robot for use 2 1 Components Unpack and locate all of the components of the robot You should have Robot base with 12V batteries 3 Batter
21. ROBOT USER S MANUAL 2009 VIDERE DESIGN 30 uint16_t pWatchDog ms int16_t pLowBattery tenths of volts int16_t pStallVal PWM counts int16_t pStallCount how long we stall in PERIOD ms increments int16_t pPwmMax PWM counts 0 will not work the motors int16_t pPwmWrap PWM timer wrap value settings for onboard control int16_t pRotVelMax int16_t pTransVelMax int16_t pRotAcc int16_t pTransAcc int16_t pRotDecel int16_t pTransDecel PID parameters int16_t pTransKp int16_t pTransKv int16_t pTransKi int16_t pRotKp int16_t pRotKv int16_t pRotKi sonar parameters int16_t pSonarConv converts from cycles to 256 mm some future expansion might take place through this mechanism char reserved 8 ERA ROBOT USER S MANUAL 2009 VIDERE DESIGN 31 Appendix B Player robot configuration file This appendix contains the Player configuration file for the Erratic Rev G base Other drivers such as the Hokuyo or SICK Laser Range Finders require their own sections in the driver See Section 5 1 and Appendix A for more information on the configuration file parameters Example file instantiating the Videre robot driver All options you might want to use are instantiated here In general the player standard units are translational velocity m s rotational velocity deg s driver Instance name of the driver name erratic Standard play
22. ation files are in usr local share player config and usr local share stage worlds The sample client executable files are in the examples libplayerc directories 3 5 PC Client software To run clients on a remote PC you must install Player Stage on that PC Please see the Player Stage documentation for information on how to do this Player Stage can run on Linux and Apple systems There is also a java client available for all systems MS Windows Linux and Apple This software can be downloaded from http java player sourceforge net Videre Design provides a Java client viewer that is useful for checking out the robot and can serve as a platform for future development 3 6 Running the Player server The software system for controlling the robot is the Player Stage system http playerstage sourceforge net The onboard PC has a full installation of the latest version of this software Figure 3 2 shows a typical system for controlling the robot The onboard PC runs the Player server which is a program for controlling the robot s motors and sensors The server takes commands and exports information to ERA ROBOT USER S MANUAL 2009 VIDERE DESIGN 14 clients that can run on the onboard PC or remotely on other PCs connected to the network Before any clients can connect to the robot the Player server must be started on the robot This is always the first step in running robot programs To start the server o
23. charger port on the left side of the robot 9 Figure 2 8 Hokuyo URG mounted on a tilt unit 9 Figure 2 9 STOC stereo device mounted on a pan tilt unit 10 Figure 3 1 Typical setup for integration of Erratic 12 Figure 3 2 Typical setup for Player server and clients 14 Figure 3 3 Javaclient Viewer program 16 Figure 5 1 Odometry coordinate system 21 Figure 5 2 Sonar placement 25 ERA ROBOT USER S MANUAL 2009 VIDERE DESIGN 4 1 Introduction The Erratic ERA mobile robot is a full featured industrial mobile robot base The name comes from the Latin errare to wander The ERA is compact and powerful platform and capable of carrying a full load of robotics equipment including an integrated PC laser rangefinder and stereo cameras We have designed the ERA to be both simple reasonably priced and highly expandable ERA was created with the experience of many years of teaching an advanced robotics course cs225b stanford edu at Stanford University as well as participation in DARPA mobile robot projects such as Centibots www ai sri com centibots and LAGR Learning And Ground Robots www darpa mil ipto programs
24. cket protocol To invoke the program connect the PC to the USB port of the controller or use the onboard PC and use robot_client lt comm port gt The lt comm port gt argument is dev erratic or dev ttyUSBn for Linux comN for MS Windows If the controller is alive the program will print a confirming message and also some information about the robot type subtype name serial number battery voltage Single character commands send command packets to the controller The character must be followed by lt CR gt to take effect Command Effect R r Turn on off raw packet printing The bytes of all packets sent from the controller are printed z print a summary of the robot state once Command Effect A a turn on off analog packet printing S s turn on off sonar packet printing i increment forward velocity m decrement forward velocity j increment left turn velocity l decrement left turn velocity space k stop motors B b right left drift increment If the robot is tethered to a keyboard and monitor or to a wired Ethernet then be careful to only move the robot a small amount ERA ROBOT USER S MANUAL 2009 VIDERE DESIGN 34 Appendix E Erratic controller packet communications This Appendix documents the format of the Erratic controller communication protocol Further details can be found in the source code for the Erratic driver in player server drivers mixed erratic
25. connection The remote PC opens a shell on the robot PC and then runs programs on the robot PC from the shell This method is similar to the Ethernet method of Section 3 2 2 It is recommended to start the Player server on the robot PC using this method Network connection In this method the remote PC runs a client application which connects to the robot PC via the network For example the user could start playerv to view the sensor readings of the robot playerv h xxx xxx xxx xxx Here the string xxx xxx xxx xxx is the IP address of the robot PC The playerv application is running on the remote PC getting data from the robot via the network connection Using the network connection many different client programs can run on remote PCs It is recommended to run GUI programs using this method since sending graphics information on the wireless interface is limited by bandwidth ERA ROBOT USER S MANUAL 2009 VIDERE DESIGN 19 5 Robot Interfaces The robot controller connects to several sensors and actuators on the robot Through the USB connection the controller accepts commands to control the actuators and sends information it collects from the sensors User programs on the PC can communicate directly with the controller using the packet protocol described in Appendix D Each sensor or actuator can be thought of as an interface The packet protocol is one way to control the interface the lowest level of control ava
26. control loop to achieve velocity setpoints using feedback from the encoders The PID parameters control the responsiveness and stability of this loop These parameters should be left unmodified unless there is a very good reason for changing them e g the robot carries a heavy payload PID values should not be changed by the user without contacting Videre Design The motor control can easily be made unstable if these values are changed The PWM and PID parameters can be set with low level packet commands or through the Player driver configuration file The following table lists the relevant parameter names and defaults Firmware Parameter Player driver config Default Effect pPwmWrap timer count motor_pwm_frequency Hz 16KHz Pulse frequency for motor current pPwmMax timer count motor_pwm_max_on fraction 0 7 Maximum duty cycle for PWM pTransKp pid_trans_p 40 Proportional value for translation PID pTransKv pid_trans_v 80 Differential value for translation PID pTransKi pid_trans_i 0 Integral value for translation PID ERA ROBOT USER S MANUAL 2009 VIDERE DESIGN 24 Firmware Parameter Player driver config Default Effect pRotKp pid_rot_p 30 Proportional value for rotation PID pRotKv pid_rot_v 60 Differential value for rotation PID pRotKi pid_rot_i 0 Integral value for rotation PID 5 5 8 Saving settings The values for some robot parameters in the configurati
27. ction The controller accepts one low level command to reset the odometry to 0 0 0 The Player driver maintains an additional transform on the odometry system so that it is possible to set the robot s pose to an arbitrary place within the odometry system There are two position2d interface commands that are relevant ResetOdometry SetOdometry x y theta The first function resets the robot pose to 0 0 0 The second sets it to x y theta within the coordinate system in meters and radians The raw cumulative odometry readings 24 bit number of counts are available from the low level interface using the packet commands see Appendix E 9 5 5 2 Enabling the motors Before any motor control commands are accepted the motors must be enabled There is a packet command for enabling the motors The Player Position2dProxy has SetMotorEnable bool will enable or disable the motors When the motors are enabled the Erratic platform will resist movement by outside forces To push the robot by hand disable the motors either under program control or by pressing the motor control button 5 5 3 Motor control modes The controller presents two different modes of controlling the 2 degrees of freedom available from the differential wheel drive In TR mode the controller sets the translational and rotational speeds or positions independently In VEL2 mode the controller sets the speed of each wheel independ
28. e onboard PC and erratic is the user name You should now be asked for a password which is erratic again At this point you will be talking to the onboard PC 3 2 3 Wireless access This is the normal way to access the robot See Section 4 for details on how to set up the wireless Ethernet connection that is built into the onboard PC 3 3 Root access For many operations such as changing the wireless configuration the user must be root The erratic user has root privileges using the sudo command In a shell you can issue any command as root by prefixing it with the word sudo e g sudo mkdir etc myfile You will be asked for a password the first time you issue the sudo command the password is the erratic user password You can also become the root user by using the following command sudo su After this all commands will be performed as root 3 4 Player software The onboard PC has a complete installation of the Player Stage software The directory structure for the development software is home erratic player 2 0 3 Player server and clients config configuration files examples libplayerc C code examples examples libplayerc C code examples home erratic stage 2 0 3 Stage robot simulator worlds simulation config files In addition the core executable files and libraries for Player and Stage are in the standard directories usr local bin and usr local lib and useful configur
29. ently Typically user programs will use the TR mode as the most convenient 5 5 4 TR mode In TR mode the translation and rotation of the robot are treated as independent values For example the forward velocity can be set to 0 3 m sec while setting the rotational velocity to 20 deg sec Figure 5 1 Odometry coordinate system Positive angles are counter clockwise X Y ERA ROBOT USER S MANUAL 2009 VIDERE DESIGN 22 Within TR mode both rotation and translation motion can be determined by either velocity or position commands For example while commanding a forward velocity of 0 3 m sec the user could also command the controller to achieve a heading of 120 degrees with respect to the odometry coordinate system Specifying translation velocity and rotation position heading is a particularly useful mode The controller automatically switches to TR mode whenever one of the TR packet commands is issued to the controller see Appendix E The Player driver uses a configuration parameter to distinguish between TR and VEL2 independent wheel velocity modes In the configuration file there is a line Set to 1 to have the driver use individual wheel control direct_wheel_vel_control 0 If this parameter is set to 0 then all position2d commands are interpreted as rotation translation commands Player provides a subset of the available TR modes Rotation and translation velocity SetSpeed functions Rotation
30. er ptz The ptz service controls up to 3 hobby type servos These servos are typically connected as a pan tilt unit for cameras or the Hokuyo laser 3 8 Running standard Player clients Once the Player server has been started on the onboard PC clients can connect to the server to control the robot and show information about the robot These clients will run on Linux and Apple systems Figure 3 2 Typical setup for Player server and clients Robot PC Player server controls motors and sensors Player clients perform high level interpretation and control Wireless Access Point 802 11 b g Network Hub Network PC Player clients perform high level interpretation and control ERA ROBOT USER S MANUAL 2009 VIDERE DESIGN 15 A client can be run on any PC that has an Ethernet connection to the robot If the client produces graphical output then typically it will run on an off board PC because transferring the graphics information across the Ethernet connection can consume a lot of bandwidth especially for the wireless connection But for a quick start you can run the clients from the onboard PC If you have an ssh connection to the onboard PC and the connection exports X windows then the client graphics will show up on your screen There are two clients that can be used to check the basic functionality of the robot playerjoy This client controls the robot via a joystick or the keyboard Start the clien
31. er option tells the driver to expose all interfaces and assigns them IDs provides position2d 0 power 0 aio 0 ir 0 Serial port to use for connecting to robot NOTE using udev rules to set up this symlink port dev erratic Maximum translational and rotational speeds accepted during operation This is also capped by robot s internal hard limits potentially lower than given here For Erratic it s about 2 m s and 720 deg s max_trans_vel 0 7 max_rot_vel 100 The robot uses these acceleration values to achieve desired velocity There is a hard minium acceleration as well as a top one set by the robot trans_acc 1 0 rot_acc 200 If set these specify the robot to use another acceleration when target velocity is zero trans_decel 3 rot_decel 300 Parameters for the PD control loop onboard the robot When in individual wheel control translation parameters are used for each wheel control Warning Changes can have unexpected effects including truly erratic behavior pid_trans_p 40 pid_trans_v 100 pid_rot_p 40 pid_rot_v 100 These set how to drive the wheel motors Frequency affects noise and perhaps power efficiency motor_pwm_frequency 16000 motor_pwm_max_on 0 7 Set to 1 to have the driver use individual wheel control PD settings for translation will be used This might be useful depending on the kind of control loop in your application but probably you want to leave it at
32. erring to the velocities of the individual wheels SetSpeed leftvel rightvel lt leftvel gt and lt rightvel gt are the wheel velocities in m sec 5 5 6 Acceleration and velocity limits The controller implements a constant acceleration velocity profile when given a velocity setpoint That is when the controller is commanded to achieve a velocity it uses a constant acceleration to change the velocity in a linear manner until the setpoint is achieved Higher values for these parameters will make the robot more perky Higher values may also help simple control algorithms which depend on a short lag time in achieving a velocity setpoint However higher values for acceleration are less safe since the robot can achieve higher speeds more quickly Sometimes it is useful to have a larger acceleration for an emergency stop For this purpose there is a separate deceleration parameter Typically it is the same as the acceleration parameter but can be set to another value Whenever the robot is commanded to zero velocity the deceleration value is used Often it is desirable to limit the velocity that the robot is allowed below the maximum achievable for example for safety The robot absolute ERA ROBOT USER S MANUAL 2009 VIDERE DESIGN 23 maximums are approximately 2 2 m s and 720 deg s The limit velocities can be set to any value below this The acceleration and velocity limits can be set using low level c
33. es and b is the vector of bytes in the packet int calc_chksum int16_t n unsigned char b uint16_t c 0 while n gt 1 c b lt lt 8 b 1 n 2 b 2 if n gt 0 c c uint16_t b return c E 5 Command packets A command packet consists of a command byte followed by an argument The command argument can be either NULL a 16 bit positive integer a ERA ROBOT USER S MANUAL 2009 VIDERE DESIGN 35 16 bit negative integer or a string of bytes Table 1 shows the format of these command types Commands should not be sent to the robot at a rate faster than 20 Hz E 6 Controller command reference A listing of the commands that can be sent to the robot and the interpretation of their arguments is given in the table below Command Num Arg Effect Open 1 None Resets origin of odometry turns motors off Should be issued when first connecting to the robot Close 2 None Turns off motors Should be issued when disconnecting from the robot Config 18 None Returns a configuration packet see Section 0 Command Num Arg Effect Enable 4 ARG Enables or disables commands to control the motors With an argument of 0 stops the motors and disables motor power motors go limp With an argument of 1 enables motor power motors are engaged the robot responds to motion commands This command must be issued before any motion takes place Set acc 5 ARG Set t
34. ew the bolt into the STOC Power and communications is supplied by a white IEEE 1394 cable The cable is attached to the top plate Insert one end into the IEEE 1394 port on the STOC device and the other end into the IEEE 1394 port on the computer Make sure the cable is free around the STOC since it must move when the pan tilt unit moves The pan tilt unit can be tested by turning on the power to the robot It should move to an upright position and stay there When the robot is turned off it is recommended to put the STOC into the stowed position 90 degrees backwards In this position the STOC is less likely to be damaged by hitting something The tilt unit can be moved by pushing gently on the base of the STOC Figure 2 9 STOC stereo device mounted on a pan tilt unit note Older model PC pictured ERA ROBOT USER S MANUAL 2009 VIDERE DESIGN 11 Please refer to the STOC User s Manual from the downloads section of the Videre Design stereo vision website for information on the operation of the STOC ERA ROBOT USER S MANUAL 2009 VIDERE DESIGN 12 3 Quick Start After setting up the robot Section 2 you should set up the Erratic PC to interact with your computer environment and run some sample programs to test the functionality of the robot 3 1 Networking environment The Erratic PC comes pre configured with an installation of Ubuntu Linux www ubuntu com Player Stage robot control softwa
35. fig_file gt and starts the driver using its parameters The standard configuration is listed in Appendix B the actual file is located on the onboard PC at usr local share player config erratic cfg In the subsections below we will describe the relevant Player driver configuration parameters 5 2 Communication port This is the PC port over which Player on the PC or any other user program communicates with the Erratic controller The standard name for this port is dev erratic This device name is a symbolic link to the actual device which is a USB serial device typically dev ttyUSB0 The PC uses udev rules set at the factory to link the port name to the correct USB serial device If a user program is communicating from a MS Windows machine the port name will be a TTY comm port e g COM6 For example the test program for the robot Appendix D will run on a MS Windows machine and it accepts the name of the comm port as an argument The Player driver finds the port name in the configuration file Serial port to use for connecting to robot port dev erratic 5 3 Robot type information There are several parameters relating to the robot type Most of these are set at the factory The user may change the name of the robot using a utility program A 1 ERA ROBOT USER S MANUAL 2009 VIDERE DESIGN 20 Parameter Default Value Name Erratic 1 Type Erratic Subtype Rev E Serial XXXX factory
36. he controller integrates the motor encoder values into 2D pose estimates X Y and angle coordinates This pose estimate is called the ERA ROBOT USER S MANUAL 2009 VIDERE DESIGN 21 odometry pose or sometimes dead reckoned pose The raw encoder values are also available to user programs Position control can be achieved at the low level through the use of packet commands sent directly to the controller From Player the position2d interface implements position control commands and returns odometry information For the C proxy the class is Position2dProxy 5 5 1 Odometry coordinate system The controller maintains an internal estimate of the pose of the robot in a global coordinate system Figure 5 1 The pose is calculated based on integrating the motor encoder readings as the robot moves The accuracy of the estimate depends on a number of factors including the type of floor smooth tile is better than carpet the speed of the robot wheel slippage bumping obstacles etc The robot position within this coordinate system refers to the position of the midpoint of the axle between the two wheels For Erratic this position is slightly forward of the center of the robot body The dimensions of the robot and the position of the coordinate reference are given in Appendix G This system is initialized to 0 0 0 when the robot is opened by a client that is the robot is at the origin pointing in the X dire
37. ilable An alternative is to use a more abstract view of the interface in which the details of the packet communication are hidden from the user Robot control software on the PC presents these more abstract interfaces to the user Erratic uses the Player Stage project for abstract interfaces which is an open source widely supported software platform This section documents the interfaces of the Erratic platform as well as the Player driver abstract interfaces that correspond to them From the client side we will use the Player C proxy libplayerc library as an example of how to interact with the Player driver The Player proxy generally uses units of meters for distance and radians for angles 5 1 Robot parameters and Player configuration file Many of the functions of the controller are modified by a set of configuration parameters These parameters are stored in flash memory on the controller and most can be changed via controller commands Appendix A is a full listing of the robot parameters for reference Here we describe parameters in more detail in the relevant subsection If you are using the Player interface many of the parameters can be changed using the Player driver configuration file for Erratic The configuration file is read by the Player driver on the onboard PC to determine the resources of the robot base Typically Player is invoked using the command player lt config_file gt This reads in the lt con
38. lagr vision htm The base platform is designed to work with an on board PC The PC runs the Player Stage open source software system www sourceforge net playerstage as well as user programs for intelligent behavior The PC has a wireless internet link for communication with off board computers ERA supports a full range of sensors including IR floor sensors sonars laser rangefinders LRFs and stereo vision The on board PC has sufficient processing power to run sophisticated processing algorithms for these sensors for example to perform 3D analysis for localization and mapping 1 1 Base Characteristics Base platform size 40 cm L x 37 cm W x 18 cm H Wheels 15 cm diameter driven 6 25 cm diameter caster Polymer core soft non marking rubber tread Wheelbase 33 cm Drive type Differential single rear caster Maximum speed 2 0 m sec 720 deg sec Motors DC reversible with gearhead 72 W continuous power Encoder resolution 500 cycles per motor revolution Controller 16 bit microcontroller Integrated controller motor driver Analog digital and servo interfaces Power 12V 7AH lead acid batteries x3 5A charger Weight 4 5 Kg base 12 Kg base 3 batteries Payload 20 Kg ERA ROBOT USER S MANUAL 2009 VIDERE DESIGN 5 1 2 Onboard PC Characteristics PC size 16cm L x 16cm W x 5 5 cm H Processor Intel Celeron M 1 4 GHz Optional Core 2 Duo Processor RA
39. less likely to be damaged by hitting something The tilt unit can be moved by pushing gently on the base of the URG 2 10 STOC installation If you have a STOC stereo camera or other camera device with your robot and it is mounted on a fixed base then follow these steps for installation Unpack the STOC and locate the x 20 threaded hole on the bottom of the STOC This hole will be used to mount the STOC on the mounting bracket Put the STOC on the thread of the mount and turn it to engage the threads and hold the STOC to the top of the bracket After mounting the STOC connect the grey IEEE 1394 cable to the STOC port This cable supplies both power and communications to the device The other end of the cable plugs into the IEEE 1394 port of the computer see Figure 2 3 Please refer to the STOC User s Manual from the downloads section of the Videre Design stereo vision website for information on the operation of the STOC 2 11 STOC installation with pan tilt unit The STOC or other camera can be mounted on a pan tilt unit see Figure 2 9 The pan tilt unit provides 90 degrees of panning motion and 60 90 degrees of tilt To install the STOC device remove all packing tape and other materials from the pan tilt unit There is a 20 bolt in the top deck of the tilt unit which fits onto a thread hole in the STOC Locate the threaded hole on the bottom of the STOC mount the STOC on the tilt unit and scr
40. o to Section 3 3 to continue 3 2 2 Wired Ethernet connection To set up the onboard PC via wired Ethernet you must have a local network that uses the DHCP protocol to assign internet addresses Plug an Ethernet cable into the Ethernet port on the back of the PC Then start up the PC by turning on the power switch of the robot and pressing the Power button on the front of the PC The disk activity LED will flash for awhile and it will take about 2 minutes to boot the PC Figure 3 1 Typical setup for integration of Erratic into a computer environment Robot PC Wireless link 802 11 b g PC Wired link to local network Wireless Access Point on local network Wireless Access Point 802 11 b g Network Hub ERA ROBOT USER S MANUAL 2009 VIDERE DESIGN 13 To access the PC you have to determine the IP address that has been assigned to the PC Often you can find this information by looking at the log files of the DHCP server contact you System Administrator for this information If you cannot determine the DHCP address you will have to use the first method keyboard mouse monitor of accessing the PC If you find the IP address of the onboard PC then you can connect to the PC using SSH Secure Shell from any computer on the local network even Windows computers if they have SSH installed Start a command window and use the command ssh erratic xxx xxx xxx xxx Here xxx xxx xxx xxx is the IP address of th
41. ommand packets or through the Player driver configuration file Unfortunately the position2d interface does not have the ability to set acceleration or velocity limits at the present time The following table shows the relevant variables Please note that the Player driver uses meters while the controller uses mm for distance Firmware Parameter Player driver config Default Effect pTransVelMax mm sec max_trans_vel m sec 1000 mm sec Maximum rotational velocity allowed pRotVelMax deg sec max_rot_vel deg sec 200 deg sec Maximum rotational velocity allowed pTransAcc mm sec2 trans_acc m sec2 400 mm sec2 Translation acceleration pTransDecel mm sec2 trans_decel m sec2 400 mm sec2 Translation deceleration pRotDecel deg sec2 rot_decel deg sec2 400 deg sec2 Rotation deceleration pRotAcc deg sec2 rot_acc deg sec2 400 deg sec2 Rotation acceleration 5 5 7 Motor PWM and PID control The motors are driven by pulse width modulation which efficiently throttles full battery current to produce slower speeds A higher PWM frequency exhibits less noise but too high can cause overheating of the drivers 16 KHz is a good compromise only dogs and small children can hear this motor whine The PWM maximum duty cycle cuts the maximum current that can be delivered to the motors For higher performance and faster speeds set this number higher The controller uses a 200 Hz
42. on file can be saved into flash memory on the motor controller of the robot The values that are saved are the rotation and translation acceleration and velocity and the PID parameters save_settings_in_robot 0 0 or 1 If the value is 1 the configuration settings are saved in flash memory Once saved it is no longer necessary to specify them in the configuration file 5 6 Analog and digital sensors The Erratic controller has a complement of analog and digital sensors Some of these are attached to fixed functions such as measuring the battery voltage or the motor current A few of them are free for use by other equipment that may be put onto the robot The analog and digital information may be accessed via the low level packet interface or through the Player driver and associated proxies Some of the fixed functions have special Player interfaces These are detailed in this section 5 6 1 Battery voltage The battery voltage is measured by a fixed analog input on the controller Its value is returned with every motor information packet in tenths of a volt The nominal voltage is 12V When the voltage goes below 11V the LED starts blinking and the batteries should be recharged The Player driver has a power interface that makes available the battery voltage to client programs The PowerProxy class has a member function GetCharge that returns the battery voltage as a floating point number 5 6 2 Analog and digital inputs
43. pen a shell on the robot PC and run the following program player usr local share player config erratic cfg This will start the player server connecting to the microcontroller via the USB port The server will print a startup message indicate that it has established communication with the microcontroller and then listen for connections from clients To stop the Player server use ctrl C or a kill command to it process The server can be restarted at any time An alternative method is to have Player start on the robot during the boot process In this way there is no need to open a shell on the robot to start Player See Appendix A for information on autostart of Player 3 7 Services The server for Erratic offers the following services depending on the peripherals that are installed position2d This is the basic service for controlling the motion of the robot and publishing the integrated position of the robot based on the motor encoders dead reckoning power Provides information about the battery voltage analog Analog voltage levels from the wheel current sensors and user analog and digital I O ir Infra red floor sensors detecting the floor in front of the robot sonar Sonar sensor service provides information about sonar ranges from the front sonar array if installed laser The laser service controls the Hokuyo URG or SICK LMS 200 laser rangefinder and publishes range scans from the las
44. r 2 byte integer Sonar range in mm byte Sonar number 2 byte integer Sonar range in mm ERA ROBOT USER S MANUAL 2009 VIDERE DESIGN 39 Appendix F Power Port The power port on the robot controller board is an 8 pin connector that provides power for peripherals The header is a polarized AMP MTA header with spacing of 0 1 inches The power pins assignments are given in Figure A 1 Normally peripherals that are ordered with the robot are connected to the power port The user can also connect his own peripherals If no peripherals are connected an empty connector should be plugged in to prevent any metal from shorting the power pins Figure A 1 Power port on top of robot Pin spacing is 0 1 inches GND 5V 5V 12 19 V 12V GND GND GND lt edge of robot top of robot ERA ROBOT USER S MANUAL 2009 VIDERE DESIGN 40 Appendix G Erratic base dimensions ERA ROBOT USER S MANUAL 2009 VIDERE DESIGN 41 ERA ROBOT USER S MANUAL 2009 VIDERE DESIGN 42
45. ranslational acceleration in mm sec sec Set max vel 6 ARG Sets the maximum translational speed of the robot in mm sec Set racc 23 ARG Sets rotational acceleration in deg sec sec Set max rvel 10 ARG Sets the maximum rotational speed of the robot in deg sec Stop 29 None Stop all translation and rotation Trans vel 11 ARG NARG Set translational velocity signed mm sec Switches to TR mode Rot vel 21 ARG NARG Set rotational velocity signed deg sec Switches to TR mode Trans pos 8 ARG NARG Set translational distance signed mm relative to current position Switches to TR mode Rot pos 12 ARG NARG Set rotational heading signed deg in odometer system No arg Positive int arg Negative int arg String arg SYNC0 SYNC1 command END SYNC0 SYNC1 command ARG low byte high byte SYNC0 SYNC1 command NARG low byte high byte SYNC0 SYNC1 command SARG count N lt 100 byte 0 byte N 1 Table 1 Format for command arguments ERA ROBOT USER S MANUAL 2009 VIDERE DESIGN 36 Command Num Arg Effect Switches to TR mode Rot relative pos 22 ARG NARG Set rotational heading signed deg relative to current heading Switches to TR mode Wheel vel 32 ARG Set velocity of two wheels independently First byte is signed left velocity 2 cm sec second is signed right velocity 2 cm sec Switches to VEL2 mode Origin 7 None Reset
46. re http playerstage sourceforge net and all drivers necessary for running the peripherals on the PC most notably the wireless device Figure 3 1 shows a typical setup for using the robot within a networked environment The robot PC has a wireless 802 11 b g link already installed This link can communicate to a wireless access point The access point is part of a wired local network and other PCs are connected to the wired network Thus the robot can communicate with any computer on the local network through the wireless access point and if the local network is on the Internet with any computer connected to the Internet 3 2 Accessing the Onboard PC You must access the onboard PC to set up the wireless network There are two modes of access Keyboard mouse and monitor Wired Ethernet connection For users who do not have much experience with Linux the first mode is recommended 3 2 1 Keyboard mouse and monitor This is the simplest way to access the PC Plug in a PS 2 mouse and keyboard in the appropriate slots on the back of the PC Plug in the monitor to the VGA connector on the back of the PC Start up the PC by turning on the power switch of the robot and pressing the Power button on the front of the PC You should see the PC boot taking place on the monitor At the end of the boot process there will be a Ubuntu Welcome screen for login Log onto the PC using User name erratic Password erratic G
47. se the ifup and ifdown commands ifdown ath0 ifup ath0 The first command stops the interface and the second starts it applying the new configuration parameters If the wireless interface has successfully connected to the local network access point it will have an IP address and be accessible over the network You can check this by trying to ping another computer on the network e g ping hostname is a command for pinging the computer named hostname If the computer does not respond check the wireless configuration settings 4 3 Finding the robot on the network The robot PC uses DHCP to find an address using the local network s DHCP server The DHCP server will assign a random IP address to the robot PC In order to communicate with the robot from an external PC it is necessary to know this IP address There are two ways this can be done Force the DHCP server to assign a fixed IP address to the robot This is possible with some DHCP servers using the MAC address of the wireless interface See the system administrator for more information Find the assigned IP address Typically the DHCP server will assign the same IP address to the robot PC every time it connects to the network You can find this address by looking at the logs of the DHCP server ERA ROBOT USER S MANUAL 2009 VIDERE DESIGN 18 4 4 Connecting to the robot There are two ways to connect to the robot from a remote network PC SSH
48. setting The lt name gt parameter is the user name for the robot and can be any string of 20 characters or less The user may change this parameter The lt type gt parameter is the class of robot For this robot the type is Erratic a differential drive small mobile robot This parameter should not be changed The lt subtype gt parameter specifies a revision or subclass of the robot The current revision is Rev E The revision number is useful when updating the controller firmware since it specifies the exact cabling and other particulars of the robot and its controller This parameter should not be changed The lt serial gt parameter is a unique serial number assigned to the robot The serial number should be used in any communications with the support team at Videre Design This parameter should not be changed These parameters are available from the low level packet interface by sending the configuration packet command The controller responds by sending a configuration response packet see Appendix E 8 The Player driver reads the robot name and type information from the controller and prints it out when it starts up but otherwise does not use it The Player configuration parameter lt name gt is the name of the driver itself not the robot This name is used as the driver name by clients that attach to the Player driver Instance name of the driver name erratic Currently Player 2 0 3 there is no Pla
49. t motor control Figure 2 5 Inserting the first battery into the slot on the right side of the chassis Figure 2 6 Three batteries installed in the back of the robot with the back plate on the right side Battery inserted into chassis Back plate with Thumb Screws Batteries ERA ROBOT USER S MANUAL 2009 VIDERE DESIGN 9 In the first two tests each motor is supplied with power You should see the robot first turn to the left right motor turning then to the right left motor turning In the second two tests the controller sets the motor speed using feedback from the encoder Again you should see the robot turning to the left and then the right It turns at a very slow speed and the speed should be constant If it turns slowly at first and then starts to speed up there is a problem with the encoder or controller for that motor 2 8 Hokuyo URG installation If you have the Hokuyo URG mounted on a tilt platform please see the next section This section is for the URG on a fixed mount If your robot was ordered with the Hokuyo URG laser the cables for this device are already installed on the robot base You must remove the blue tape that secures the cables and connect the cables to the URG and to the PC refer to Figure 2 2 There are two cables that are mounted on the robot base One is an 8 pin cable that connects into the URG It supplies power to the URG The other end is connected to the robot base
50. t with the command playerjoy g lt xxx xxx xxx xxx 6665 gt The optional argument lt xxx xxx xxx xxx 6665 gt is used when playerjoy is started on a remote network PC xxx xxx xxx xxx is the IP address of the robot PC The g argument uses incremental keyboard control which is a useful way to move the robot These are the key assignments for motion o i move forward o move backwards o j rotate left o l rotate right o k lt space gt stop Pressing any of the motion keys more than once will increase the speed in that direction playerv This program presents a graphical interface for viewing the robot s laser rangefinder and for moving the robot playerv h xxx xxx xxx xxx The optional argument is used when playerv is started on a remote network PC xxx xxx xxx xxx is the IP address of the robot PC Playerv will open a graphic window that shows the robot s motion and sensor information You must subscribe to the robot s services to display them or to control the robot To subscribe to the laser device use the Devices gt laser menu item You should see a representation of the robot s laser scan after you subscribe To control the robot subscribe to the following three items Devices gt position2d gt Subscribe Devices gt position2d gt Command Devices gt position2d gt Enable You can now control the robot by dragging the control icon in the middle of
51. th argument 1 Encoder packets give the raw 24 bit encoder values for the left and right wheels Type Value byte Header 0x90 3 byte integer Left wheel encoder value 3 byte integer Right wheel encoder value E 10 Analog packet Analog packets are sent continuously when the analog packet command has been issued with argument 1 Analog packets give the state of the 4 A D converters as well as 3 digital inputs Analog values are from 0 1023 10 bits This specifies a linear range from 0 3 5V Type Value byte Header 0x9A byte Number of analog readings 4 2 byte integer First analog reading left motor current Current is approximately 25 mA x Value 2 byte integer Second analog reading right motor current Current is approximately 25 mA x Value 2 byte integer Third analog reading user input 2 byte integer Fourth analog reading user input ERA ROBOT USER S MANUAL 2009 VIDERE DESIGN 38 Type Value 2 byte integer Digital I O bit 0 left floor sensor 0 is floor 1 is no floor bit 1 right floor sensor 0 is floor 1 is no floor bit 2 user input E 11 Sonar packet Sonar packets are sent continuously when the sonar packet command has been issued with argument 1 Sonar packets give the state of the 8 sonars in the front sonar ring Sonar values are in mm Type Value byte Header 0x9B byte Number of sonar readings in the packet byte Sonar numbe
52. the configuration file PID values should not be changed by the user without contacting Videre Design The motor control can easily be made unstable if these values are changed Firmware Parameter Player driver config Default Effect pPwmWrap timer count motor_pwm_frequency Hz 16KHz Pulse frequency for motor current pPwmMax timer count motor_pwm_max_on fraction 0 7 Maximum duty cycle for PWM pTransKp pid_trans_p 40 Proportional value for translation PID pTransKv pid_trans_v 80 Differential value for translation PID pTransKi pid_trans_i 0 Integral value for translation PID pRotKp pid_rot_p 30 Proportional value for rotation PID pRotKv pid_rot_v 60 Differential value for rotation PID pRotKi pid_rot_i 0 Integral value for rotation PID A 5 Saving parameters to flash The current parameters can be saved to flash by issuing the Save Params packet command Section E 6 Some of the parameters can also be saved via the Player driver configuration file Section 5 1 Once saved they become the default parameters when the robot is turned on A 6 Parameter structure Parameters are held in a structure that can be read out on request to the controller For reference here is the structure struct parameters char pName 20 char pType 20 char pSubtype 20 char pSN 10 uint8_t pVersion uint8_t pSubVersion uint8_t pBaudHost uint8_t pBaudAux uint16_t pRevCount ERA
53. the window 3 9 Running the Javaclient Viewer The Javaclient viewer is available from Videre Design check the Download pages under Support You must have JRE Java Runtime Environment 1 5 installed to run the Viewer For developing programs with Javaclient you also should install the JDK Java Development Kit See http java player sourceforge net To start the Viewer client on Linux systems run java jar DoViewer jar and on MS Windows systems just double click on DoViewer jar The Viewer GUI will start looking like Figure 3 3 The Host field is for the address of the robot PC typically it will be a local DHCP derived If the robot is tethered to a keyboard and monitor or to a wired Ethernet then be careful to only move the robot a small amount If the robot is tethered to a keyboard and monitor or to a wired Ethernet then be careful to only move the robot a small amount ERA ROBOT USER S MANUAL 2009 VIDERE DESIGN 16 address unless you have set up the robot with a DNS name If you are running Viewer on the robot use localhost After specifying the host address use the Connect menu to open a connection to the robot If the address is correct and Player is running on the robot then Viewer will open the connection and list the services available in the text viewing area at the bottom of the GUI The buttons on the left will be enabled for the corresponding service To view the sensors click
54. there is no way to turn them off Motor packets contain basic information about the state of the robot and its motors as well as integrated odometry information Values larger than a byte are always inserted with the least significant byte first Type Value byte Header 0x8n lt n gt is 2 if the robot is not moving and 3 if it is 3 byte integer Odometry X position in signed mm ERA ROBOT USER S MANUAL 2009 VIDERE DESIGN 37 Type Value 3 byte integer Odometry Y position in signed mm 2 byte integer Odometry heading in degrees 0 360 2 byte integer Left wheel velocity signed mm sec 2 byte integer Right wheel velocity signed mm sec byte Battery voltage 1 10 volts byte Motor stall status bit 2 set for left wheel stall bit 3 set for right wheel stall 2 byte integer Heading target in deg 0 360 Only valid if rotational position control command has been sent 2 byte integer Distance target in signed mm Only valid if translational distance control command has been sent E 8 Configuration packet A configuration packet is sent in response to a configuration command 18 The configuration packet has all the information of the configuration structure Section A 6 Type Value byte 0x20 byte Parameter version N bytes Configuration structure as a sequence of bytes E 9 Encoder packet Encoder packets are sent continuously when the encoder packet command has been issued wi
55. using Make sure the battery charger is turned off before plugging it in there is a power switch on the side of the charger Plug the power cord of the charger into a power socket Plug the charging plug of the charger into the charging port on the side of the robot see Figure 2 7 Turn the charger on The red LED indicates that the charger is working The other LED will be orange when the batteries are being charged and green when they are fully charged Charging takes 1 2 hours for a full charge depending on the state of the batteries The charger supplies 5 amps which is strong enough to charge the batteries even when the PC is running the PC will draw about 2 amps You may operate the robot PC while the charger is plugged in However be careful not to run any programs that cause the robot to move 2 7 Basic motor test To test the motors and the controller either put the robot on blocks so its wheels are off the floor or put it in the middle of the floor with the charger cord disconnected During the test the robot will move slowly in a small circle so you don t need a lot of space Turn on the robot and note that the green LED becomes lit Then press and hold the motor button down for about 3 seconds The green LED will switch to orange indicating the motor test will begin when you let go of the button The robot will now test each motor in sequence Right motor power Left motor power Right motor control Lef
56. y charger Compact PC Cables USB and computer power Laser rangefinder if ordered Refer to Figure 2 2 which shows the robot base and other components to be mounted onto the robot The PC charger and cables are in the box The cabling for the computer and other devices is connected to the robot base and held in place with blue tape Remove the blue tape wherever you find it on the robot base 2 2 Connecting the computer The computer is installed onto the robot base prior to shipping but with several cables disconnected for safety reasons Locate the antenna connector and power connector on the side of the PC see Figure 2 3 The power connector should be on the right side of the robot looking from the front see Figure 2 2 In the white box came antenna It must screwed onto the Wireless Antenna Terminal see Figure 2 2 for wireless operation Figure 2 1 Components for the Erratic robot Unpack the small box to access the PC cables and battery charger For installation the main power switch must be in the OFF position Leaving the switch ON RESET during installation can result in damage to the robot and injury to the user Figure 2 2 Top of the robot populated with a computer and cable connections Front of robot is at the bottom of the image Battery Charger and Peripherals Three batteries with plugs Erratic base Wireless antenna terminal USB and power to PC and peripherals Onboard PC US
57. yer driver has a sonar interface that accumulates sonar readings and makes them available to client programs The SonarProxy class can be Figure 5 2 Sonar placement The sonar numbers are given in the figure 0 1 1 2 3 4 5 6 7 ERA ROBOT USER S MANUAL 2009 VIDERE DESIGN 26 used to get the readings Use the function double SonarProxy GetScan int ch to retrieve the range of sonar lt ch gt Range values are in meters The placement of the sonars is as in Figure 5 2 above the coordinates of each sonar can be retrieved with the GetPose ch function 5 8 Servo motors The Erratic controller supports a connection to 3 hobby type servo motors These motors can be controlled through low level packet commands or through the Player driver via the PTZ interface The low level packet interface is documented in Section E 5 Each of the servos can be individually set to a position using these commands The Player PTZ interface can be used to control the servos There are two PTZ interfaces one for a full pan tilt device on servos 1 and 2 ptz 0 and one for a tilt only device on servo 0 ptz 1 ERA ROBOT USER S MANUAL 2009 VIDERE DESIGN 27 6 Technical Support For technical support please contact Videre Design by email or FAX Videre Design 865 College Avenue Menlo Park CA 94025 Fax 650 323 3646 Email support videredesign com and please CC sales videredesign com ERA ROBOT
58. yer interface to the type information of the robot 5 4 Player interface list The Player driver provides interfaces to the various resources of the robot base These include motor control battery power analog and digital I O IR floor sensors and sonars Note that the laser rangefinders are handled as separate drivers connected to the PC and are not configured through the Erratic robot base driver All interfaces presented by the Player driver must be listed in the interface list Standard player option tells the driver to expose all interfaces and assigns them IDs provides position2d 0 power 0 aio 0 ir 0 sonar 0 ptz 0 5 5 Position control The Erratic controller drives the robot wheels using an integrated dual H bridge motor driver The driver is able to supply up to 30A at 12V to the motors although in practice the current is limited to less than this The motors are rated at 75W continuous power and are able to drive the robot at speeds up to 2 m sec and 720 deg sec Each wheel is controlled independently allowing the robot to turn as well as drive forwards or backwards differential drive The controller also connects to the motor encoders which count 500 cycles per revolution of the motor axis effectively 38400 counts per revolution of the wheel With this resolution the controller can implement very stable feedback motion control even at very slow speeds lt 1cm sec In addition t

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