Mobile Agents. Uwe Lämmel. Hochschule Wismar Wismar University of Technology, Business, and Design Business School. Mobile Agents LEGO RCX -1 -

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1 Mobile Agents Hochschule Wismar Wismar University of Technology, Business, and Design Business School

2 Contents RCX-LEGO-Robot: The Hardware The LEGO Programming Environment Not Quite C and the Command Center Examples Agents and Robots Delphi and the RCX Java and the RCX -2 -

3 RCX The Hardware LEGO MINDSTORMS bit Hitachi H8 microprocessor 16K internal ROM 32K static RAM, 6K "user memory" only Firmware: bytecode interpreter -3 -

4 RCX - Components 3 input ports (sensors) light-, touch, temperature-, rotation- 3 output ports (motors) Infra red interface User interface: LCD display, 4 buttons On/Off, Prgm, Run, View Power supply: 6 x R6 : 6 x 1,5V = 9V sound (programmable) -4 -

5 The LEGO Programming Environment RIS - Robotic Invention System graphical programming environment simple statements O.K. for children -5 -

6 Not Quite C and the Command Centre RXC Command Center Mark Overmars, Dep. of Comp. Sc., Univ. Uetrecht Version 3.01, October 1999 NQC programming environment Direct control of the RCX Monitoring the RCX Bricx Command Center John Binder Enhanced Version of the RcxCC -6 -

7 NQC - Not Quite C Drive in a square #define Tahead 150 #define Tturn 198 #define Nrepeat 4 #define ML #define MR #define MM OUT_A OUT_C ML+MR task main() { repeat (Nrepeat) { SetPower(MM,4); OnFor(MM,Tahead); SetPower(ML,2); On(MR); Wait(Tturn); }// repeat Off(MM); }//main -7 -

8 Sensors in NQC SetSensor(SENSOR_1, SENSOR_TOUCH); // Defines sensor 1 as a touch sensor Sensor configuration Type Values ClearSensor() SENSOR_TOUCH touch 0 - not pressed / 1 - pressed no SENSOR_LIGHT light from 0 (dark) to 100 (bright) no SENSOR_ROTATION rotation 16 for one rotation yes SENSOR_CELSIUS temperature Celsius *10 no SENSOR_FAHRENHEIT temperature Fahrenheit * 10 no SENSOR_PULSE touch number of touches yes SENSOR_EDGE touch number of state transitions yes -8 -

9 task, function, subroutines Tasks - up to 10 tasks - a program must have a task main - activate a task : start name; - stop a task : stop name; Attention: task sensor_task( ) {... } start sensor_task; stop sensor_task; -9 -

10 task, function, subroutines Subroutines - up to 8 subroutines may be defined - Do not call a subroutine from different tasks! - If called from different tasks then we can not define local variables. - real subroutine, one code section only. - no parameters -10 -

11 task, function, subroutines Functions - "inline function" - not a real subroutine: each call to a function results in another copy of the code being included - Parameters possible: int by value const int by value only constants int& by reference only variables const int& by reference argument can not be changed -11 -

12 task, function, subroutines Makros text substitution definition of constant values grouping statements possible #define turn {Off(MM);OnFwd(MR); \ Wait(80); Off(MM);} - no parameters -12 -

13 Examples Go on a Line Obstacle detection by sending messages Thinking in Rules Where I am? Going on a squared world Synchronisation of Tasks Light Sensor and Fuzzy Variables -13 -

14 Go On a Line # define DARK 45 task main(){ SetSensor(SENSOR_2,SENSOR_LIGHT); while(true){ OnFwd(OUT_A+OUT_C); if (SENSOR_2<DARK){// dark-> turn to light Off(OUT_C); }; //if if (SENSOR_2>DARK){// bright -> turn to dark Off(OUT_A); }//if }//while }//main -14 -

15 Obstacle detection by sending messages #define Turn_left #define Turn_right {OnRev(ML);Wait(T_Turn);OnFwd(ML);} {OnRev(MR);Wait(T_Turn);OnFwd(MR);} task send_signal() { while(true){ SendMessage(SIGNAL); Wait(T_Signal);} } //send_signal task check_signal(){ while(true) { lastlevel = SENSOR_1; if(sensor_1 < lastlevel - RECEIVE) if (Random(2)==0) Turn_left; else Turn_right; }//if }//while }//check_signal -15 -

16 Values of the light sensor blue: 30 cm away from wall red: 15 cm away from wall Light sensor receives the sent messages -16 -

17 Thinking in Rules //-- Rule based programming task rulebase() { while (true) { if(ls<dark) // on a line - go ahead {stop search; state=0; OnFwd(MM);} if(tl==1 TR==1) // obstacle - turn back {stop search; back; state=0;} if(ls>dark && state==0) // off line-search {state=1; start search;} if(timer(0)>t_prog_max) // time over {Off(MM); StopAllTasks();} }//while }// rulebase -17 -

18 Where I am? Going on a squared world fixed start position see the lines sending coordinates correct direction -18 -

19 In a Squared World task mainloop() { while (true) { state=3; getnewcoordinates(); // while goal position not reached do while(ypos!=ydest XPos!=XDest) { setdirection(); turn(); horizontalline(); }//while goal not reeached goalreached(); }//while(true) }//mainloop -19 -

20 Squared World - Detecting a Line do{ //while until (state==1 state==2); // horizontal line if (state==1) {// right eye looks at the line i=0; // try to see the line with the other eye: while(sl<grey&&i<ncorrsteps) { OnFor(ML,T_corr); i++; } } // here the same for left eye looking at the line if (i==ncorrsteps){ // line not found go back and try again if (state==1) OnRev(ML); else OnRev(MR); Wait(T_turnback); OnRev(MM); Wait(T_back); state=0; } } while (i==ncorrsteps); // while line not found -20 -

21 Synchronisation of Tasks no synchronisation: every task controls the motors in parallel stopping tasks: only one task at a time controls the output a task starts always from the very beginning Using semaphores: motor control is synchronised suspension of task is programmed -21 -

22 No Synchronisation task main() { SetSensor(TS,SENSOR_TOUCH); start check_sensors; while (true) { OnFwd(MM); Wait(Tgo); // go a line OnRev(OUT_C); Wait(Tturn); }//while }//main // turn a right-angle task check_sensors() { while (true) { if (TS == 1) { // obstacle touched OnRev(MM); Wait(Tback);// going back OnFwd(OUT_A); Wait(Tturn);// turning OnFwd(OUT_C); }//if }//while }//check_sensors // Go ahead again -22 -

23 Stopping Tasks task move_square() { while (true) { OnFwd(MM); Wait(Tgo); // go a line OnRev(OUT_C); Wait(Tturn); }//while }//main // turn right-angle task check_sensors() { while (true) { if (TS == 1) { // obstacle touched stop move_square; OnRev(MM); Wait(Tback);// going back OnFwd(OUT_A); Wait(Tturn);// turning OnFwd(OUT_C); // Go ahead again start move_square; }//if }//while }//check_sensors -23 -

24 Semaphore task move_square() { while (true) { until (sem==0); sem=1; OnFwd(MM); sem=0; Wait(Tgo); until (sem==0); sem=1; OnRev(OUT_C); sem=0; Wait(Tturn); // turn }//while }//main // wait for access // go a line // wait for access task check_sensors() { while (true) { if (TS == 1) { // obstacle touched until (sem==0); sem=1; // wait for motor access OnRev(MM); Wait(Tback); // going back OnFwd(OUT_A); Wait(Tturn); sem=0; }//if }//while }//check_sensors // turn -24 -

25 Light Sensor and Fuzzy Variables Fuzzy-values for different grounds 1,00 0,80 0,60 0,40 0,20 white area green line black line black area 0,

26 What is a Robot? Illustrated oxford Dictionary, Oxford, 1998: a machine with a human appearance or function like a human a machine capable of carrying out a complex series of action automatically a person who works mechanically and efficiently but insensitively -26 -

27 A robot A brain controls actions and responds to sensor signals. A body holds all the parts together. Actuators allow the robot to move. Sensors give information about the environment. A power source. Mobile robots: tethered autonomous -27 -

28 Delphi and LEGO-OCX LEGO MINDSTORMS Software Developer Kit Spirit.OCX install Spirit.OCX into Delphi Use a TSpiritCtrl object in an application: myrobot : TSpiritCtrl; -28 -

29 Drive in a Square using Delphi-OCX procedure TLEGOMAIN.DownLoadProgButtonClick(Sender: TObject);... begin myrobot.selectprgm(prog2); myrobot.beginoftask(mytask); myrobot.setpower('motor0motor2',con,4); myrobot.setfwd('motor0motor2'); myrobot.loop(con,4); myrobot.on_('motor0motor2'); myrobot.wait(con,tahead); myrobot.off('motor0motor2'); myrobot.on_('motor0'); myrobot.wait(con,tturn); myrobot.endloop(); myrobot.endoftask; end; -29 -

30 import josx.platform.rcx.*; public class Distance { public static boolean go=true; public static void main(string[ ] args){... SendSignal sender = new SendSignal(); Watcher see sender.start(); see.start(); }//main }//Distance = new Watcher(); lejos Program class SendSignal extends Thread { static final byte[ ] message = {-1}; public SendSignal(int millisec) {... } public void run() { while (Distance.go) { Serial.sendPacket(message, 0, 1);... }//while }//run }//SendSignal -30 -

31 lejos-api: class summary -31 -

32 lejos Java for the RCX Java-based operating system (~16k) programs: > lejosfirmdl // download the lejos-firmware > lejosc // Java-Compiler, uses jdk > lejos // download a program into the RCX needs: JDK Java Communcations API Include lejos path into PATH variable SET RCXTTY=COM1-32 -

33 lejos extension of TinyVM TinyVM Object oriented language (Java) Preemptive threads (tasks) Arrays, including multi-dimensional ones Recursion Synchronization Exceptions lejos A Windows version Floating point operations (doubles truncated to 32 bits) String constants Casting of longs to ints and vice versa Marks references in the stack (garbage collection possible) Multi-program downloading java.lang.math sin, cos, tan, atan,