Introductory Robotics Workshop “Successful Strategies in Robotics”

1. Introductory Robotics Workshop “Successful Strategies in Robotics” Terry Grant, NASA, Ames Research Center Jeneva Westendorf, Foothill High School 2/5/04 2/12/04

2. Outline • 2/5 • Introductions • Team Building & Strategy • Robotics Hardware & Software Architecture • Programming in C Introduction – with the HB • 2/12 • Review: Robot Project Requirements & Example • Object Avoidance Mission • Go + Throw Example • Teacher as Coach • Wrap-up

3. Team Development • Forming • Create Ground Rules/ Key Result Statement • Gain Buy-in on Code of Conduct • Discuss Roles • Storming • Establish Trust • Manage Conflict • Norming • Solve Problems • Make Decisions • Performing • Start competition strategy & plans

4. Team Strategy & Plans • Translating a Challenge into Requirements • Robot physical capabilities • Robot behavior (high level code) • Operator – robot interaction • Assigning tasks and milestones • Writing a total schedule (initial and revised) • Plan to test capabilities & behavior • Plan for full robot tests & re-planning • Plan for team coordination meetings

5. Robot Building & Coding • Completed LEGO robot from MLCAD • Ref: http://www.lm-software.com/mlcad/ • Art of LEGO Design • http://handyboard.com/techdocs/artoflego.pdf • Pictures and Code from the Jan ’03 Workshop • http://robotics.nasa.gov/edu/BBworkshop03 • IC4 Environment downloads: • http://www.botball.org/about_botball/ic4.html • Hands-on Challenges Ref: • http://robotics.nasa.gov/students/challenge.htm

6. Robotics H/W & S/W Architecture Bot Multi-tasking S/W Components Real-Time Operating System * P-code interpreter * Input/Output Drivers - Clock * Load/Run modes Handy Board or RCX H/W *Central Processor * Random Access Memory * Special I/O Circuits * Battery & Power Conditioner Interactive C v. 4.10 * Editor * Debug Interpreter * Loader Other Apps Desktop Operating System Desktop Hardware IR for RCX* Serial Data Interface Charger (HB only) Lego Mechanical Lego Motors & Sensors

7. Robot Project Requirements • Hardware configuration and general environmental constraints • Operator Requirements • Controller requirements All Three Elements are needed and should be written down for a common team understanding

8. Programming in C - Introduction • IC4 provides an editing, compiling, and downloading environment for either RCX or Handy Board. • Follows C syntax (grammar) • Uses functions < xyz() > declared and called • Many functions for Input/Output are preloaded in a library • Good tutorial examples provided with the application • Multi-tasking capability in O.S. • allows sampling & holding multiple conditions in parallel: position, direction, and other sensors

9. General Syntax • declaring: output type Function(inputs e.g.int x, int y) {block ofstatements} • calling: Function(x, y); • types: int x, y, z; float a, b, c; all variables must have a declared type. • global types are defined at the top, outside of a function, and usable by all functions.

10. Introductory Checkout • This workshop will use the Handy Board (HB) controller and a pre-built demo robot. • Checkout your configuration and understanding of the concepts by entering and downloading the following one line program to send a message to the HB display screen: Void main() { printf(“Hello <your name> \n”); } • Open Interactive C to view the actual environment & write the above code, then run it.

11. Simple Example Make a Robot Go Forward and Return • H/W & Environment: Build a bot with the HB or RCX, wired to motors such that forward power moves wheels forward, and put on a demonstration table with enough flat surface • Operator: Write the code, load the microcontroller, and initiate the execution (running) of the code • The controller: Turn on the motors forward, wait 2 seconds, reverse the motors, wait 2 seconds, then stop.

12. IC4 voidmain() { fd(0); fd(2); sleep(2.0); bk(0); bk(2); sleep(2.0); off(0); off(2); } Open Interactive C & write the code Simple Code Example

13. More Basics • Three modes: off, standby, run • Use of ‘Interaction’ window in IC4 • Test new functions for I/O, robot behavior • Check list of library functions, global variables • Download firmware • Upload Arrays for spread-sheet analysis • Edit aids • Auto-indentation • Parenthesis matching • Syntax checking (on download) • Use of ‘save as’ to file new, or trial code

14. Notation of IC 4 IC notation is the same for RCX & HB if ("condition") { "statements" } else { "statements" } while ("condition") { "statements" }

15. Defining a function or task: xxx “name”() { "statements" } xxx = ‘void’ if no return variables = ‘int’ if integer return variables = ‘float’ if floating point return variables Notation of IC4 -2

16. Notation of IC4 - 3 Starting and ending parallel tasks: pid = start_process(taskname()); kill_process(pid);

17. Inputs for RCX - light(y) for y = 1,2, or 3 - light_passive(y) - digital(y) or touch(y) Notation of IC4 - 4

18. IC Outputs Motor outputs, ports 0 to 3 for HB(or A to C for RCX) To use port 1: fd(1); forward, positive voltage bk(1); backward, negative voltage Motor(1, x); x = -100 to 100 off(1); leave port ‘open’ brake(1); for the RCX only, to brake the motor Notation of IC4 - 5

19. Notation of IC4 - 6 To display on Controller LCD e.g. printf(“Hello\n”); printf(“X= %d\n”, x); /*x is an integer */ printf(“X= %f\n”, y); /*y is floating point */ printf(“%d -%d\n”, a, b); /*a & b are integers */ In the RCX only five characters total can be displayed, and “\n” is not needed.

20. Object Avoidance Example

21. Requirements • Robots with range sensors start facing each other about one foot apart. • Robots must start when a button is pushed or the light comes on. • Robots must stop after T (5-15) seconds. • The first robot to touch the barrier loses. Starting Light 4’ x 4’ barrier Bot 1 Bot 2

22. Object Avoidance Behavior • Display program title • Wait for start_button push, then beep • Wait 3 seconds to start • Go straight forward • while T is not exceeded, Turn if an object is sensed • When T is exceeded stop

23. Object Avoidance Code /* bang-bang control to avoid obstacles using rangefinders - Grant 1/27/04*/ /******************** Robot port configuration ***********/ #define R_MOTOR 2 /* motor port 2 */ #define L_MOTOR 0 /* motor port 0 */ #define R_ENC 1 /* encoder 1 is digital port 8 */ #define L_ENC 0 /* encoder 0 is digital port 7 */ #define L_RANGE 18 /* range sensor in analog 18*/ #define R_RANGE 16 /* range sensor in analog 16*/ #define THROW_DIST 195 /* sensor reading to throw the ball, avoid obstacles, etc*/ #define T 5000L /* run time in millisec */ /*********** globals for left and right sensors, bumper *****/ int L_Range, R_Range, Bumper=0, L_Enc, R_Enc;

24. Object Avoidance Code - cond void main() { start_process(monitor_sensors()); printf("range avoid press start\n"); start_press(); sleep(3.); /* wait for start button press */ avoid(); } void monitor_sensors() { enable_encoder(R_ENC); /*enable the encoders */ enable_encoder(L_ENC); while(1){ Bumper=digital(15); /* front bumper switch */ L_Enc=read_encoder(L_ENC); R_Enc=read_encoder(R_ENC); L_Range= 255-analog(L_RANGE); /* range reading is big for big distances */ R_Range = 255-analog(R_RANGE); defer(); } }

25. Object Avoidance Code - cond void avoid() { int l_speed, r_speed; long time_s=mseconds()+T; while(!stop_button()&&(mseconds()<time_s)) { l_speed=r_speed=75; if(L_Range<=THROW_DIST) r_speed=0; else { if(R_Range<=THROW_DIST) l_speed=0; } motor( L_MOTOR, l_speed); motor(R_MOTOR, r_speed); defer(); } ao(); }

26. Light Trigger Calibration • Hardware & Environment • L1 is the remote trigger light. • L2 is the room lighting. • Pd photodetector has a wide field of view. • The Controller display helps the operator measure both the dark and light response. • The controller [HB or RCX code] sets the “light vs. dark” threshold and waits for the threshold to be exceeded to trigger the action.

27. Avoidance - Sensor Test Project • To support a robot avoidance contest with a light start, design a robust light trigger for the action which runs the avoidance behavior for 5 seconds after a light is turned on. • Discuss all requirements (total group) • Write a code design for each Bot. • Write and debug the code • Participate in an Avoidance contest • Compare trigger and behavior designs and results

28. Avoidance - Sensor Test Behavior e.g. • Display program title [for a few seconds] • While start_button is not pushed, • Display sensor level and • Prompt for start_button push • While stop_button is pushed, display and increment the trigger threshold • When start_button is pushed, • Display sensor level • Wait for sensor level to cross the trigger threshold, then go forward, etc as original object avoidance • When T is exceeded: stop, • display “done” for a few seconds