Design of an Obstacle Avoidance Vehicle Frank Scanzillo EECC657

Objectives Detection and avoidance of obstacles Detection of and navigation toward light beacon (final destination of vehicle)

Specifications Maximum distance from tank to beacon: 7.8 m Accuracy of destination: 25 cm radius Minimum dimensions of obstacles: 23.5 x 23.5 cm, height 9 cm Maximum height of obstacles: 20 cm Minimum height of beacon emitter/detector: 25 cm No objects within 3 cm of vehicle prior to system power-up Tank Light detector stand Photo light detector Obstacle IR beacon (target) Infrared object sensors 7 cm 25 cm 18 cm Optoreflector 1 cm

User Interface Power on/off LED status lights – Normal operation – Target reached – Vehicle stuck Power Switch On Status Lights Off L2 Failure L1 Success L0 Normal

Microcontroller Interfaces System block diagram Microcontroller Port APort BPort AD Sensor outputs DC motor inputs FLFR Status light outputs LSFRSF LSRRSR RLRR Photo ML1MR1 ML0MR0 L2 L1 L0 Opto

Analytical Component Required type, number, and configuration of sensors Calculation of sensing distances – Stopping distance – Effective turning radius – Sensor body dimensions/beam widths Calculation of object size limits Algorithm for system (flowchart)

Sensors Used Sharp GP2Y0A21YK (4) Sharp GP2Y0D340K (4) Panasonic PNA4602M 38 kHz IR Photodetector Optek OPB745 Optoreflector

Sensor Configuration Photo light detector Infrared object proximity sensors Infrared sensor beams L W ½W½W ½ L SS2SS2 S SV 2 S SH 2 S FV 1 S FV 2  SV S FH 2 SF2SF2 SS1SS1 SF1SF1 S FH 1 S SV 1  FH S SH 1  SH  FV WOWO

Sensor Configuration (cont.) R 2 = 90 

Calculation of Sensing Distances (front/rear) Stopping distance: d S = cm Virtual turning radius: zero Effective turning radius: d = cm t = 1.74 cm Sensor body dimensions: GP2Y0A21YK: 4.46 x 1.35 cm Beam width: S FV1 ’ = t + d S +  FV + E FV1 + E SFV1 = S FV1 ’ = cm S F2 > 28.8 cm (upper bound) S F1 < 7.35 cm (lower bound)

Calculation of Sensing Distances (side) Sensor body dimensions: GP2Y0D340K: 1.5 x 0.9 cm Distance of beam vertex from vehicle: cm Photo light detector Infrared object proximity sensors Infrared sensor beams L W ½W½W ½ L SS2SS2 S SV 2 S SH 2 S FV 1 S FV 2  SV S FH 2 SF2SF2 SS1SS1 SF1SF1 S FH 1 S SV 1  FH S SH 1  SH  FV WOWO  SH = cm S SH1 = d SS +  SH +   SH = S SH1 = cm  SV = cm S SV2 = L -  SV + E SV + E SSV2 = 37.5 – 8 + ( ) + 1 S SV2 = cm S S2 > 34.7 cm (upper bound) S S1 < cm (lower bound)

Object size limits W O = 23.5 cm (minimum width of each obstacle) Photo light detector Infrared object proximity sensors Infrared sensor beams L W ½W½W ½ L SS2SS2 S SV 2 S SH 2 S FV 1 S FV 2  SV S FH 2 SF2SF2 SS1SS1 SF1SF1 S FH 1 S SV 1  FH S SH 1  SH  FV WOWO

System Flowchart

Current Status Finalized proposal Obtained/purchased tank, logic gates, LEDs, some sensors and batteries Modified tank chassis Eliminated excess wiring Tested DC motor inputs/outputs Obtain voltage regulators, NiMH batteries/charger, HC12 board, a few more sensors Set up and test voltage regulators Set up, align, and test sensors Develop device drivers and test all interfaces System level coding, testing and verification Prepare final report/demo

Test Plan 1. Voltage regulators Verify that supply voltage for motors/sensors and beacon = V Voltage regulator output (adjustable) for microcontroller = V 2. Object sensors Position small object (i.e. 2V for both front/rear sensors, and that voltages are equal. Position either side of vehicle directly next to wall; verify that output > 1.2 V from closest front/rear sensor. Follow similar procedure to verify alignment and range of side proximity sensors. 3. DC motors: Write code to sample all five legal functions of motors (i.e. forward, reverse, turn left/right, stop), for 2 seconds each, ensuring that the vehicle moves as instructed. The vehicle should move in a straight line forward or backward, and have no virtual turning radius. 4. Beacon/photodetector: Verify that the frequency of oscillation is kHz, and that the photodetector can sense the beacon up to 8 meters away. 5. Optoreflector: Verify that a “good” logic high (> 4.3 V) is produced when a reflective strip is 1 cm from the lens, and that a “good” low (< 0.8 V) is produced when there is no reflective strip present. Write some code to test the output of the optoreflector and verify that the correct binary values are stored.

Test plan (cont.) System level test cases: – Place vehicle in a closed room with several obstacles scattered, and the beacon placed at the far end of the room. Turn the vehicle so that the photodetector is facing the direction opposite the beacon and turn the power on. Verify that the tank reaches its target before powering down. – Surround the vehicle with obstacles in an enclosed area. Place the beacon outside the enclosed area and verify that the “stuck” status light is triggered.

Power Consumption M68HC12: 350 mW expanded mode DC motors: (500 mA)(5V) = 2.5W each Object sensors: (40 mA)(5V) = 200 mW each Beacon (555 Timer): (5V)(15mA) = 75 mW Optoreflector: 100 mW LED mW photodarlington IR Photodetector: 200 mW Total power dissipation: (2.5) + 0.2(8) = W

System Cost

Q&A