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1. to the serial interface of the driver to the server 2 The first PC is called Server because it is connected to the manipulator drivers trough two RS232 interfaces one for every arm and also because it runs the server part of the software of the control system The server is the center of the control system In fact it collects the command sent by the client in custom protocol and translates it in serial commands for the manipulator The server checks the correctness of the manipulator state and if correct sends commands to the manipulator The server grants the feedback both with respect to the plant and to the clients closing the control loop of the system In fact it reads the current state of the manipulator as response of TPS command to the serial interface of the driver and sends the updated state to the clients by TCP IP connection 3 The other PC s are called client because they run the client part of the software of the control system They are connected to the server by a TCP IP network and allow the user authentication through user name and password The client is the tool that allows the user to control the system by a graphical interface containing the graphical representation of the manipulator the textual representation of the robot state button setting control parameters and sending commands to the manipulator The client also closes the control loop by TCP IP connection When the user tells a command the s
2. appears to the user see fig 5 It consist in many parts in order to simplify the plant control e In the upper part there is the button menu bar that allows to send the most important commands to the server These commands are setting commands for important variables movement direction and resolution maximum speed and acceleration during the movement etc incremental movement commands in the joint space for the specified arm for an angle equal to the current resolution in the current direction e In the central part there are two fields the left one is the graphical and textual representation of the current state of the robot arm the right one shows the information flow between the clients and the server The graphical representation is very simple the two arms are represented by two red lines with two red circles as a motor The yellow circle represents the possible trajectory of the second arm supposing motionless the first The blue box represents a hypothetical obstacle near the manipulator The black circle represents the end effector e In the bottom part there is the text field which allows the user to send particular commands to the server or a text message to the other clients connected like in a simple chat apriProg salvaProg aprixy Salvaxy apriDati salvaDati salvaConsol apriConsol tetalVer tetalVel tetalAcc teta2Ver teta2Vel teta2Acc Dim reset RobOnLine aggiorna cmd da controllore gt mov
3. hypotheses about the type of network in other words we can chose an heterogeneous network containing wireless links UMTS IEEE 802 11 WI fi Bluetooth Satellite etc that can give many advantages First we can put the plant on a mobile support working with more motion freedom We also can work on uncovered land with a Satellite communication It is obvious that the performances are worse than in the traditional wire network but we have the advantages we have already described The use of Java languages to develop the Client Server software control system permits to work in a multi tasking mode so the Server can serve many users at the same time The user connected to the server can have different roles such as a full control of the plant or a supervision if it simply observes the state of the plant 5 Hardware and Software Environment It is important to underline the very exiguous requirement of software of the control system It simply needs a standard PC that can run the Java Runtime Environment JRE version 1 3 or later The server also needs two standard RS232 interfaces and the Java Comm API 6 Start Up the control s software In order to start the server part firstly we must connect the two RS232 interfaces to the driver and the network cable to the LAN or establish the communication for other types of link in use Then we turn on the IMI robot and start the server with the command at the prompt Java ManRo
4. with an obstacle feta r teta1 0 i 80 40 40 RobOffLine ostacolo 80 80 40 40 Fig 7 Ambiguous problem demonstration Q 8 Conclusion and Further Work This paper present the work in progress of a Java Client Server controller for a robotic manipulator The control software accomplishes its objective of maintaining the control of the robot via the Internet in general connection The client interface allows the user to move the arms with the same precision of the original system The feedback information is provided by an update flow of the robot state The control system is closed loop type because it is made up of three control loops between clients and server Server and drivers and at the end between drivers and the arm s motor Further developments include task oriented manipulation rather than step by step control to teta2 49 3 ris 49 3 permit the programming of the manipulator operation and in general to add functionality and to increase the control possibilities starting from the inversion of the mouse graphical selected x y coordinates Other future works are on line estimation of the plant model parameters web access to the collected data and to port the client window towards any Mobile Phone supporting Java 2 Micro edition J2ME in order to supervise and or control the remote plant References 1 L Sciavicco B Siciliano Robotica Industriale modellistica e controllo di manipolat
5. 0 s Te1A 0 0 s2 Te2A Fig 5 The Client window When the server receives a command changing the manipulator position and its state it will send the manipulator state update in broadcast mode to the clients updating the window In fig 6 we can see a collection of manipulator configurations On the left there is the manipulator at the limit of the work space In this position if the client tries to move up the joint the server checks the robot model without sending any command to the driver because the robot can not move the arm in this direction In this position the client can move the joint only in the direction to leave the work space limit On the right three canonical positions The Home position is represented by thetal O0 radians and theta2 0 radians In the same figure we can see the configuration thetal 90 radians and theta2 90 radians and thetal 90 radians and theta2 90 radians teta1 90 0 a teta2 90 0 tetal 123 18593 teta2 123 18593 teta1 123 18593 ide teta1 90 0 a teta2 90 0 J Fig 6 Work space limit and canonical position On fig 7 we show the ambiguous problem obtained when we try to invert the cinematics of the robot manipulator The x y coordinates of the end effector is the same in both cases but on the left theta2 is positive in the right one theta2 is negative In the first case we do not have a collision but in the second we can have a collision
6. Real Time Remote Control of a Robot Manipulator using Java and Client Server Architecture F M RAIMONDI L S CIANCIMINO M MELLUSO Dipartimento di Ingegneria dell Automazione e dei Sistemi D I A S Universita di Palermo Viale delle Scienze 90128 Palermo ITALY Abstract The control of complex systems through PC networks is becoming increasingly important nowadays both in the industries and in R amp D centers In this paper a novel architecture is described which provides 24 h a day access to a remote system for remote control or supervision The system can be controlled by any PC s integrated in a TCP IP network using a Client Server communication The Client Server protocol is a custom light textual protocol that allows the fast update of the plant model also using a very small bandwidth communication link The server controls the plant through two RS232 interfaces connected to the driver of the planar manipulator with two links and two non flexible joints The clients are connected to the server through a TCP IP network and they are granted plant control and supervision privileges through authentication The client is made up of a console window representing the present state of the system both in textual and in graphical form This window also contains the buttons which allow the control of the manipulator Key Words Remote control Planar Manipulator Internet Client Server Real Time RS232 Java communication protocol 1 I
7. and light protocol allowing a real time control of a Remote Manipulator by a computer on a Local Area Network or Internet In order to minimize data transmission data transmission time problem of unpredictable communication speed and network bandwidth capacity we use a mathematical model of the robot arm in its environment We also employ the network Server PC internet Client PC Fig 1 Remote Control System Principle Scheme 2 Main Characteristics The control system is made up of a standard network supporting TCP IP protocol stack with two or more PC s and a two link planar manipulator see fig 1 The roles of this elements are 1 The two link planar manipulator is the plant to be controlled It consist of two main parts the drivers and the arms see fig 2 The two arms are moved by two Brushless motors one for every arm The drivers implement the RS232 interfaces which interpret their input as a command or a setting instructions The drivers give the motors the appropriate current for the movement They also implement the local position control loop see fig 3 using a resolver for the feedback All the parameters of the local Position Control separately for the two driver can be set via RS232 interface by the Client part of the control system to adjust the performance of the system The driver also close the control loop with the server using the serial interface the feedbak is the response of TPS command
8. boServer lt port gt where the port parameter is the server TCP IP connection local port B 0 x elimina statoRobo aggiornad cmd da controllore lt mov fia 82 42381647801483 fib 65 07518792735753 2 controllore comado mov valido inoltro comando via seriale RS232 3 giovanni serialMsg agg fia 82 42381647801483 fib 65 07518792735753 4 maurizio RoboOnLine false RoboPort response null comunicazione seriale attualmente non disponibile agg fia 82 42381647801483 fib 65 07518792735753 teta2Verso false debug del mov agg statoRobo aggiornag cmd da controllore gt mov fia 47 820810759755034 fib 6 852238334972893 comado mov valido inoltro comando via seriale RS232 serialMsg agg fia 47 820810759755034 fib 6 852238334972893 RoboOnLine false RoboPort response null comunicazione seriale attualmente non disponibile agg fia 47 820810759755034 fib 6 852238334972893 msg da controllore lt terminato programma in memoria Fig 4 The Server Interface To start the Client we employ the command at the prompt Java ManRoboClient lt address gt lt port gt where the port parameter is the local port of the client TCP IP connection and the address parameter is the server s IP address When the first user begins to connect to the server the serial communication were set up and the client server application is ready for the remote control system 7 Client Window Use After authentication the client interface
9. ed in TCP protocols and flows under Ethernet like network The second is between server and manipulator and flows in RS232 standard interfaces The server manipulator in the future S M protocol is a low level protocol highly dependent from the hardware drivers of the manipulator It was developed by NSK s engineers and it is immutable The client server in the future C S protocol is a high level protocol developed to allow simple unambiguous communication between clients and server This protocol is independent from S M so we can use the same protocol to control different plants and we can change it without changing the S M protocol The server part executes the conversion from C S to S M protocols so we can update the server without changing the client part The information flow between client ad server in most cases consists in instructions about robot setting such as maximum acceleration or maximum velocity during movement and motion command in the joint space The server examines all messages that come from client and if the message is recognized as a valid command or setting it updates the state of the robot to check if the setting or the command is valid in the current state In this case it will send the message to the robot using the S M protocol The S M protocol is made for serial communication It is a textual protocol where the messages are made up by key words representing a command or a variable and or it depends on
10. erver sends a response to confirm the command and it depends on the case sends the update state of the manipulator The Client and Server programs are written in 100 pure Java This grants the Multiplatform of the software which can run under Microsoft Windows Unix Like Operative Systems or in general under any operative system supporting Java like Palm OS etc Fig 2 IMI Planar Manipulator Feed forward compensation Position loop proportional controller Position loop integrator Velocity loop proportional controller Velocity loop integrator Digital filter Current circuit OBVL iLL p3 Pesition data NF NS Power amplifier Position command input Pulse train Input AS 232G command DEWPL hiot r currerit Resolver signal processor Resolver signal output Poeton date Velocity data Resolver Motor Fig 3 Position Control block diagram 3 Communication Protocols A communication protocol is a set of key words and grammatical rules allowing unambiguous communication between two or more entities that want to exchange information In this application we use two protocols in order to make the client server communication independent with respect to the server manipulator communication It is important to underline the difference between the two communication protocols The first protocol is employed between client and server encapsulat
11. fia 82 42381647801483 fib 65 07518792 comado moy valido inoltro comando via seriale RS232 serialMsg agg fia 2 42381647801483 fib 65 07518792735753 RoboOnLine false RoboPortresponse null comunicazione seriale attualmente non disponibile debug del mov agg statoRobo aggiornad cmd da controllore lt mov fia 47 820810759755034 fib 6 85223833 comado mov valida inoltro comando via seriale RS232 serialMsg agg fia 47 820810759755034 fib 6 852238334972893 RoboOnLine false RoboPortresponse null comunicazione seriale attualmente non disponibile msg da controllore lt terminato programma in memoria debug del mov agg pe statoRobo aggiorna cmd da controllore gt lt mov fia 42 17918924024496 fib 6 852238334 comado mov valido inoltro comando via seriale RS232 serialMsg agg fia 42 17918924024496 fib 6 85223833497 2893 RoboOnLine false RoboPort response null comunicazione seriale attualmente non disponibile debug del mov agg statoRobo aggiornad cmd da controllore gt lt mov fia 7 576183521 9851745 fib 65 07518797 Meta 378 9337 cla Ag 9 ris 2 0 comado mov valido inoltro comando via seriale RS232 ye 3164932 y2 06 0 serialMsg aga fia 7576183521 9851746 fib 65 07518792735753 etal Verso V RobhoOnLine false RoboPortresponse null ee Bas ita 1 1367785 comunicazione seriale attualmente non disponibile oar gt 41 99 127045 y1 13 184435 Te2 65 x2 136 73904 y2 45 852314 TelVer Te2Ver Telvel 0 0 s Te2vel 0
12. ntroduction to transfer using the light textual protocol only the In classical telerobotics the feedback of rich data variations of the mathematical model state which are such as live video picture from the physical very small in comparison with the live video and hardware to the operator site via Internet or mobile easily transferable in every network state So users communication links is bandwidth limited and are able to control the position of the robot arm to contains uncertain delay Examples of this approach view the graphical representation of the robot and its environment in real time without add on DSP from are Mercury project 3 and Telegarden project 4 en every position on Internet where users were able to control the position of the robot arm and to view the scene as a Series of periodically updated static images Problems with static pictures can be avoided by using video technology Video transfer is currently the hardest task to be performed within data transmission via Internet The transfer of fluent video demands a high bandwidth capacity therefore such approach clearly needs a high speed network to achieve the on line control of the robot The data transmission time across Internet depends heavily on the transient loading of the network making direct teleoperation unsuitable for time critical and dangerous interactions In this paper we present a Client Server architecture with an innovative couple of plant model
13. ori McGraw Hill libri Italia Milano 2000 2 Megatorque Motor System User s Manual NSK Ltd 1995 3 K Goldberg M Maschna Center S et al Desktop Teleoperation via The WWW Roc Of IEEE International Conf On Robotics and Automation 1995 4 http telegarden aec at 5 J Sanchez S Dormido R Pastor F Morilla A Java Matlab Based Enviroment for Remote Control System Laboratories Illustarated Whith an Inverted Pendulum IEEE 2004 6 S Chakrabarti L Wu S Vuong V C M Leung A Remote Controlled Wireless Enabled Enviroment University of British Columbia Vancouver Canada IEEE 2004 7 R Safaric I Hedrih R Klobucar Remote Controlled Robot Arm University of Maribor IEEE 2003 8 A Malinowski T Konetski B Davis D Schertz Web controlled Robotic Manipulator using Java and Client Server Architecture Bradley University IEEE 1999 9 I F Darwin Java Cookbook Solutions and Examples for Java Developers cap ll Programming Serial and Parallel Ports O Reilly 2001
14. stem The max resolution of the S M protocol is 0 01 degree so we can not overcome this precision With regard to the performance we estimate the time necessary to send a command from client to server to elaborate the message by server to update the local model to send the command to the driver To simplify the compute we can suppose null the elaboration time in the server so we can simply compute the time transmission in network and in the serial RS232 interface As to the serial RS232 interface since the driver needs a velocity equal to 9600 b p s suppose we send 10 char we spend about 10 9 9600 9 3 ms The transmission time in network is limited only by the technology used If we suppose a standard 100Mb s to send 10 char we spend about 10 9 100000000 0 0009 ms and if we have a dial up connection with V 90 standard modem we can suppose 50kb p s so we spend about 10 9 50000 1 8 ms In this case if we consider the Round Trip time we spend about 2 9 34 1 8 22 2ms to send the message to the server to send it to the manipulator and to receive the response With Regard to the unpredictable delays the very small dimension of the TCP IP packets let us think they will be minimal compared to the packets dimension In conclusion we can say that the precision is the same of the robot arm and the response time is very little so we have a very real time remote control system It is important to underline that we do not have to make
15. the case and information data in numeric format such as velocity acceleration or angle For example to set the maximum velocity to 1 5 r p s we must send the string MV1 5 plus carriage return code ODh or char r The driver will give back the echo of the string plus line feed code OAh or char n In case of syntax error the command will not be recognized and the driver will give back the echo plus a question mark to notify the error In case of correct syntax the command will be executed and the driver will give back the echo plus a prompt as notify Since there is one driver for every link the C S protocol is able to made control one link at the same time with an appropriate command For example to set the maximum velocity of link 1 to 1 5 r p s if the actual maximum velocity is 0 5 we will the client have to send the string setResolution thetal Speed the first line sets the resolution of the incremental command like tetalVel to 1 0 the second line sets the maximum velocity to 0 5 1 1 5 r p s To decrease the maximum velocity simply change tetalVel with tetalVel When the server receives the two commands it updates the local model and sends the appropriate command to the driver and to all the client connected 4 Performance In the preceding paragraph we overviewed the C S and S M protocols In this paragraph we will study the performance and the precision of the control sy

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