Ben Fluehr, Derrick Lam, Brett Melonis, Alex Person

Overview  Work Completed Car Motion Control – Servos Car Vision – CMUcam Car Steering – Magnetometers Car Obstacle Avoidance – Range finders  Work Remaining

Car Motion Control  Electronic Speed Controller (ESC)  Single steering servo  Controlled via Handy Board

ESC Control  Pulse Width Modulated (PWM) control signal from Handy Board  Draws power from battery  Grounded to Handy Board

Steering Servo Control  Pulse Width Modulated (PWM) control signal from Handy Board  Draws power from ESC  Grounded to Handy Board

Motion Control Example #use "servo_a5.icb" #use "servo_a7.icb" #define MOTOR_NEUTRAL 3040 #define STEERING_NEUTRAL 3000 #define NORMAL_SPEED 3350 void drive_forward() { servo_a5_pulse = NORMAL_SPEED; } void brake() { servo_a5_pulse = MOTOR_NEUTRAL; } Void steer_straight() { servo_a7_pulse = STEERING_NEUTRAL; } #use “servo_a5.icb” #define MOTOR_NEUTRAL 3040 #define NORMAL_SPEED 3350 void accelerate() { int i; for (i = MOTOR_NEUTRAL; i <= NORMAL_SPEED; i + 10) { servo_a5_pulse = i; }

Car Vision - CMUcam 1

CMUcam Main Loop void main() { //Initialize camera init_camera(); clamp_camera_yuv(); //Main loop while(1) { if (track_red() > 40) { //Stop sign found } if (track_yellow() > 40) { //Yield sign found }

CMUcam Detecting Blobs int track_red() { if (trackRaw(180,220,40,65,85,115) > 0) { return track_confidence; } else return 0; }

CMUCam Continued  int trackRaw(int rmin, int rmax, int ymin, int ymax, int bmin, int bmax)  Uses CrYCb instead of more commonly known RGB space  A box bounds the pixels within color boundaries, and the amount of pixels within box determines the confidence rating  Must calibrate color ranges in track’s room with actual signs

Magnetometer – Eval Board  Pre-mounted Components HMC1052L MOSFET reset Amplifier circuitry  Five Holes Vcc and GND Out1 and Out2 Set

Magnetometer – Behavior  Neutral Voltage = Vcc / 2  Voltage changes more as distance decreases  Magnetic field strength Strongest at poles and weakest in between Very strong fields cause problems Point axis towards pole for best results

Magnetometer – Behavior (cont.)

Magnetometer – Code void CheckMagnetometer() { int reading = analog(MAGNET_PORT); int absDiff = abs(reading - neutral); if (absDiff > MAGNET_THRESHOLD) { ChangeSteering(absDiff); neutral = analog(MAGNET_PORT); }

Car Obstacle Avoidance  Original plan Maxbotix Range Finder Analog output  Problem Still having jumpy output in the distances of interest Increased code complexity Difficulty responding to small changes in distance

Solution  Sharp Range Sensors Use infrared instead of sonar Should “see” a narrower range Only requires power, ground, analog output  May combine multiple sensors Sharp GP2D12: 10 – 80 cm Sharp GP2Y0A02YK: 20 – 150 cm MaxSonar-EZ1: 15 – 645 cm

Sharp Range Sensors  GP2D12  GP2Y0A02YK  Sensor Cable

Interactive C Example #define PORT 5 /* 7 available ports */ void main() { int distance = analog(PORT); /* 0 to 255 */ if (distance > 128) /* half max distance */ brake(); }

Work Remaining  Mount components in final position Glue Pieces of plastic  Combine code to run simultaneously Code finished for each component Can probably call functions in turn from main loop Possibility: multiple processes ○ Support from Interactive C ○ Spawn from any C function ○ Each runs for 5 ms

Questions?