program interpreter and communication server for an industrial robot
Contents
1. destination module Program interpreter and communication server for an industrial robot controller 37 7 Remote BackEnd process 1 Computer Teach Pendant Other equipments robots systems Single Board Computer synchronisation ISA PC 104 LCD Controller Motion controller 1 Motion controller n FTC 1018 Stepper Motor Optical Stepper Motor Optical Encoder Encoder Wafer Handling Robot Fig 2 FTC 1018 robot controller The Program Interpreter compiles the user s robot programs and executes them The Program Interpreter uses the Backend process for controlling the robot movements and also for their simulation It executes user commands like stop pause restart execution of the user program and transmit robot position The messages between the Program Interpreter and Communication modules pass via the Engine Manager The messages that show the state of the controller are shown on the LCD screen This is made by using the LCD Controller Communication module The LCD is controlled via the ISA bus The software modules written by the authors are the Communication modules the Engine Manager and the Program Interpreter The language used is the C language 2 The controller management The Engine Manager module s role is to start the modules monitor the state of the modules handle errors and supervise the good functionality of the controller The functionality of the Engine Manager is shown2. U P B Sci Bull Series C Vol 75 Iss 4 2013 ISSN 2286 3540 PROGRAM INTERPRETER AND COMMUNICATION SERVER FOR AN INDUSTRIAL ROBOT CONTROLLER Laurentiu DUCA Anton DUCA Cornel POPESCU Adrian PETRESCU This paper describes the implementation of the program interpreter and communication server for a wafer handling robot controller This is a complex robot controller software system with a very flexible operator interface The program interpreter executes the robot programs which are transmitted by the user via the communication server The work is done by a modular system in which every component has a strictly defined role Keywords robot controller program interpreter communication server 1 Introduction Robots are complex systems that combine mechanical elements such as gears electromechanical devices such as motors digital circuits such as processors and smart sensors and software programs such as embedded controllers They have computation sensing and communication capabilities Robot motion planning and control is the problem of automatic construction of robot control strategies from task specifications given in high level human like language The challenge in this area is the development of computationally efficient frameworks allowing for systematic provably correct control design accommodating both the robot constraints and the complexity of the environment while at the same time allowing for expressive tas
3. and control the errors and unpredictable situations that might appear This way the Engine Manager controls connecting and disconnecting of the user remote client the end of the execution of the user defined robot program which implies Interpreter reset and other similar situations The main disadvantage is that the messages between two distinct modules for example the Interpreter and the Communicater are delayed by passing through the Engine Manager So in the time that the robot is executing a movement the BackEnd process needs almost all of the processor resources for the motion control algorithm That s why the sending of the position to the master computer by intermediating the Engine Manager may conduce to less resources being available for the BackEnd process This can be avoided by direct sending of the position reporting from the BackEnd to the Communicater An alternative to implement the Interpreter module in other part than the controller and by this way to free up some space on the controller was to put it on the user remote workstation But then the execution of the instructions specifics to robot movement would had less control of the robot then it has now as being close to the robot drivers If only the Interpreter s Compiler module would have been put on the user remote workstation then a solution to serialize the compiled code of the user programs should be imposed but this is too complex In this version the use
4. bot controller 41 Recetver Listener reader blocking wait Reset request to yes C manager packet too small Send disconnect Send packet to C manager to C manager Fig 6 The Listener process workflow 4 The program interpreter As shown in figure 7 the program interpreter Interpreter is made by three parts Interpreter Manager Compiler and Executer Interpreter Manager Backend gt Engine process Manager t Executer Compiler Interpreter a Fig 7 The program interpreter The Interpreter Manager waits for commands to arrive from the user remote computer via the Engine Manager The command from the Engine Manager may be to set some parameters like animating the robot movement or 42 Laurentiu Duca Anton Duca Cornel Popescu Adrian Petrescu execution or simulation of a new program When the command is to execute a user defined robot program the Interpreter Manager asks the Compiler to compile the program into an internal structure recognized by the Executer and then request the Executer to run the program At the end of the execution the Interpreter will clean up memory and exit and the Engine Manager will create another Interpreter process The program execution is shown in figure 8 The instructions are executed sequentially one by one until the end of the program If at the execution of some instr
5. h the Cartesian coordinate system REFERENCES 1 S Mokaram Mobile robots communication and control framework for USARSim Intelligent and Advanced Systems Conference ICIAS 2012 2 S Arias A N gre N Turro Evolution of the robotic control frameworks at INRIA Rh ne Alpes Control Architectures of Robots CAR11 Inria 2011 3 K Koz owski Robot Motion and Control Control and Information Sciences Springer 2011 4 A Twanjing N Tsuawei The SHR 3000 robot user manual Jel Press 2008 5 C Stanciu L Duca FTC 1018 robot controller user manual FerroTech manuals 2010 6 M Stanciu L Duca The Ferroeng language reference manual FerroTech manuals 2010
6. handling and is used for producing industrial equipment and for wafer quality inspection It can move simultaneously on all the axes For more info see 4 The architecture of the FTC 1018 robot controller is shown in figure 2 The role of the robot controller is to execute the programs made by the user in order to control the movements of the robot here the SHR 3000 robot on each of the three axes The movement of the robot on each axis is made by the electrical motors The position on each axis is shown by the optical encoder of the corresponding axis The controller commands the hardware driver of the motor on an axis and reads the position from the optical encoder of that axis The motor drivers are controlled via the ISA bus Using the remote computer the user creates robot programs and transfers them by using the FTP protocol to the controller s single board computer The user handles the controller by command messages sent and received by using the RS232 communication or the TCP IP communication modules which transmit them to the Engine Manager Those commands are of type execution simulation pause restart stop program reboot controller send position The Engine Manager supervises the well functionality of the controller It is an intermediate module for all the modules in the controller functionality flow All the commands from the software modules go to the Engine Manager except transmit position command which routes them to the
7. igure 5 The communication manager waits for input blocking read and when it receives a packet it first checks for input errors If no error occurred and the packet is from the Engine manager then it will send it to the user remote workstation If the packet comes from the Listener and it is not a disconnect request or a reset request then it will send the packet to the Engine manager 40 Laurentiu Duca Anton Duca Cornel Popescu Adrian Petrescu Comunication Manager TCP Disconnect req Distroy listener Announce E disconnect yes no Send packet to E Fig 5 The communication manager workflow The functionality of the Listener process is described in figure 6 The Listener process permits the user to disconnect and reconnect It makes a blocking listen in waiting for a message from the user client or for a connection request If the user wants a new connection then the Listener will send to the communication manager a reset request and the connection will be served If a new packet arrives and it is not too small then the Listener will send the packet to the communication manager In this version the user must be in the same LAN network as the controller In future versions there are planned message encryption between the user and controller and authentication of the user when connecting to the controller Program interpreter and communication server for an industrial ro
8. in figure 3 The controller starts up with the creation of the Engine Manager Then are created the software modules communication queues and the processes 38 Laurentiu Duca Anton Duca Cornel Popescu Adrian Petrescu Communicater Interpreter Program Interpreter and Backend Now the modules are ready to handle the user requests and the main execution flow is started up When no command is arrived from the user the Engine Manager is idle It can receive messages from the Interpreter or from the Communicater The input errors are fatal errors because we assume no errors come at communication between modules Engine Manager Crete C I B Input Errors Reboot req Fatal error ni Send comunication owoff command ruvsim Destroy I and B Set General Crash Reboot request Send packet to C Send packet to I Eno Fig 3 The Engine Manager s module workflow The program shut down implies destroying all the modules which is made after checking that the robot does not move in any way After program shut down the system can be rebooted by the user by pressing the reset button When the Interpreter fails to compile a user program or it ends the execution of the user program requests its reset from the Engine Manager The Interpreter s reset is done by killing the Interpreter process and starting a new one If the Interpreter wants to send a message to the user li
9. k specifications Several aspects of control solutions for industrial robots have been addressed in the literature including communication and control strategies The References section includes a sample of this research and recent publications covering advances in this area include 1 2 and 3 The application presented here is part of an automated system which may be programmed to make all the possible movements of a robot from the Assistant professor Automatics and Computers Faculty University POLITEHNICA of Bucharest e mail laurentiu duca cs pub ro Lecturer FElectrotehnics Faculty University POLITEHNICA of Bucharest e mail anton_duca yahoo com Professor Automatics and Computers Faculty University POLITEHNICA of Bucharest e mail cornel popescu cs pub ro Professor Automatics and Computers Faculty University POLITEHNICA of Bucharest e mail adrian petrescu cs pub ro 2 36 Laurentiu Duca Anton Duca Cornel Popescu Adrian Petrescu semiconductor industry who manipulates silicon wafers between different machine tools The system is shown in figure 1 ROBOPAK Robot Control Sofware Sample of a wafer manipulation cycle Lo Fig 1 The robot controller system The system has three parts the SHR 3000 industrial robot 4 the FTC 1018 robot controller 5 and ROBOPAK software package used to be the interface for the system user The industrial robot SHR 3000 is a 3 axis robot made for silicon wafer
10. ke the robot position or program compilation error then the Engine Manager transmits it to the Communicater Program interpreter and communication server for an industrial robot controller 39 The Communicater may send to the Interpreter an information message for example user disconnected or a command message run simulate wait resume program position reporting on off In this case the Engine Manager sends this message to the Interpreter 3 The communication server The communication server makes the link between the controller and the user remote workstation Remote PC In figure 4 is shown the structure of the communication server also called Communicater Receiver ay i Communication Listener 39 Remote PC manager Engine Manager e Communication Server Fig 4 The communication server The communication manager handles all the communication server activity It takes messages from the user or Engine Manager and places them from one to another The Communicater must always be ready to receive messages from the user remote workstation even when it wants to transmit messages to the user Input from the user remote workstation is taken with the Receiver Listener process The Listener takes messages from the user workstation and sends them to the communication manager The functionality of the communication manager is described in f
11. r must be in the same LAN network as the controller In future versions there are planned message encryption between the user and controller and authentication of the user when connecting to the controller The user programs have a very simple structure being the equivalent in C of the main procedure The authors did not include procedures and functions to the Ferroeng robot programming language That made a simpler program interpreter In the implementation of the lexical analyzer and parser it were used tools like bison and flex tools which made the implementation of the Interpreter easier Compiling the user programs is made by a single pass through the program text In future developments there are planned optimizations of the compiler The grammar of the user programming language is similar to ANSI C This model has lot of advantages like conflicts elimination and the fact that the operator priorities are already established by the C language The language covers all the movements that a 3 axis robot can made The movement of the robot in a fixed Cartesian point can be made at the level of the user program instruction 44 Laurentiu Duca Anton Duca Cornel Popescu Adrian Petrescu both by serializing the movements on each axis or by parallelizing the movements on all robot axes at the same time The portability of the programs on different robots is made by the fact that the robot programming language offers instructions that works wit
12. uction an error appeared then the execution ends and the error will be signalized to the user remote client via the Engine Manager Between the execution of two consecutive instructions the Executer verifies if a new command has arrived from the user In the case that the new command is to end program or execute new program the current execution stops otherwise if the command is to set up robot position reporting or wait resume program the command will be executed and then the program continues with the next instruction Executer C stat gt Execute next instr l New command Get input Error return error Last instruction no retum succes Stop program aa Normal command return succes animation wait resume Fig 8 The Executer workflow The user programs are written in the Ferroeng language which is a language defined by the authors and its grammar is similar to the C language For more info consult 6 Program interpreter and communication server for an industrial robot controller 43 5 Conclusion The implementation of the Engine Manager as a separated module and process brings advantages and disadvantages The main advantage is that in any of the states of a dedicated module for example if the Interpreter would be executing the user program there is the Engine Manager who is available to receive messages from any module
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