Introductory Robotics Workshop “Successful Strategies in Robotics”

Terry Grant,NASA, Ames Research Center

2/1/05

2/8/05

Outline• 2/1

– Introductions – Team Building & Strategy– Robotics Hardware & Software Architecture– Programming in C Introduction – with the HB

• 2/8 – Review: Robot Project Requirements & Example – Object Avoidance Mission– Go + Throw Example– Pre-Botball suggestions– Wrap-up

Team Development

•FormingCreate Ground Rules/ Key Result StatementGain Buy-in on Code of ConductDiscuss Roles

•StormingEstablish TrustManage Conflict

•NormingSolve ProblemsMake Decisions

•Performing•Start competition strategy & plans

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

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

• IC5 Environment downloads:– http://www.botball.org/about_botball/ic5.html

• Hands-on Challenges Ref:– http://robotics.nasa.gov/students/challenge.htm

Robotics H/W & S/W Architecture

Interactive C v. 4.10* Editor* Debug Interpreter* LoaderOther Apps

Desktop Operating System

Desktop Hardware

Bot Multi-tasking S/W Components Real-Time Operating System * P-code interpreter * Input/Output Drivers - Clock * Load/Run modes

HB, Sumo11, RCX or XBC H/W*Central Processor* Random Access Memory* Special I/O Circuits* Battery & Power Conditioner

Serial Data Interface

Charger (HB only)

Lego Motors& Sensors

LegoMechanical

IR for RCX*

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

Programming in C - Introduction• IC5 provides an editing, compiling, Simulation and

downloading environment for either RCX, Sumo11, Handy Board & XBC.

• 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

General Syntax

• declaring:

output type Function(inputs e.g. int x, int y) {block of statements}

• 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.

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.

Simple Example

Make a Robot Go Forward and Return– H/W & Environment:

Build a bot with the HB or other controller, 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.

Simple Code ExampleIC4

void main()

{

fd(0); fd(2);

sleep(2.0);

bk(0); bk(2);

sleep(2.0);

off(0); off(2);

}

• Open Interactive C & write the code

The Development Cycle• Analogous to the action of a race car team

– Initial requirements reflect conceptual performance objectives

– After design and test, additional objectives are added, and a new design and test begins, etc.

• What improvements in behavior are desired? [wait for start, balance motor power]

• What code style improvements will aid maintenance? [use of defines, functions, comments]

* See example improvements in code

More Programming Basics• Three modes: off, standby, run

• Use of ‘Interaction’ window in IC– 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

Three Coding Behavior Scripts

• Linear:– Do A;– then do B;– then do C;– then do D;– etc.

• Branch: - If(condititon){

Do A;

then do B;

etc.}

- Else{

Do C;

then do D;

etc.}

• Loop: while(condititon){

Do A;

then do B;

etc.}

Then do C;

then do D;

etc.}

Notation of IC 5IC notation is the same for all branches & loopsif ("condition"){ "statements"}else{ "statements"}

*condition example: (x>y)

while ("condition")

{

"statements"

}

Notation of IC5 – con’d 2

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 IC5 – con’d 3

Starting and ending parallel tasks:

pid = start_process(taskname());

kill_process(pid);

Notation of IC5 – con’d 4

IC OutputsMotor outputs, ports 0 to 3 for HB, XBC(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 [backward] to 100 [forward]

off(1); remove voltage; leave port ‘open’

Several new motor functions on XBC see manual

Notation of IC5 - 5

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 XBC the display area is 14 rows of 28 characters. - New display functions add to display options.In the RCX only five characters total can be displayed,and “\n” is not needed.

Object Avoidance Example

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.

Bot 1 Bot 24’ x 4’ barrier

Starting Light

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

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 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 SPEED 70#define DELTA 0#define T 5000L /* run time in millisec *//*********** globals for left and right sensors, bumper

*****/int L_Range, R_Range;

Object Avoidance Code - condvoid main(){ start_process(monitor_sensors()); printf("range avoid press start\n"); start_press(); sleep(3.); /* wait for start button

press */ avoid();

}void monitor_sensors(){while(1){

L_Range= 255-analog(L_RANGE); /* range reading is

big for big distances */ R_Range = 255-analog(R_RANGE); defer(); }}

Object Avoidance Code - condvoid avoid(){ int l_speed, r_speed; long time_s=mseconds()+T; while(!stop_button()&&(mseconds()<time_s)) { l_speed=SPEED,r_speed=SPEED+DELTA; 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();}

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 sets the “light vs. dark” threshold and waits for the threshold to be exceeded to trigger the action.

Avoidance - Sensor Test Project

• Change object avoidance requirement to use 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 a light-started Avoidance contest• Compare trigger and behavior designs and results

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 [or use knob() to set 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

Go-Throw Example

Go - Throw Requirements

• Behavior Requirements: Assume a wall with the target basket and the robot pointed at the basket. Robot goes forward at a speed which slows to a minimum at the throwing distance and then throws a ping pong ball and stops.

• Robot Characteristics: Handy Board robot with motor steering, a throwing arm with a motor that holds the ball, 2 range sensors, and shaft encoders on each drive wheel.

• Operator sets the throw distance and arm height, points the robot and starts the processor action.

• The controller powers the drive motors, reads the shaft encoders and adjusts the motors to go straight. It also reads the range sensors to set the speed to slow at the throw distance, then activates the throw motor and stop.

Code DesignStart sensors monitoring [monitor_sensors()]

Find selected behavior [Go+Throw]

• Wait for ‘Start’

• Sound “beep”

• wait for operator to remove hand

• while(ave. range > throw distance) {

go straight [(ave. range- throw dist.) sets speed]

}

• throw ball, then turn motors off

*See actual code

Testing, Tuning, Setting Parameters

• Try it out!– See how straight the robot runs– Adjust the throw height– Adjust the throw distance (change #define

THROW_DIST and reload)

• How much uncertainty do you observe?

• What could be changed to improve the throwing accuracy?

Pre-Botball Suggestions

• See Botball 2005 Pre-Workshop Activities

Wrap-up Discussion

• Did you learn what you expected?

• What issues were not addressed?

• What did you like?

• What did you find less useful?