Design of an Obstacle Design of an Obstacle Avoidance VehicleAvoidance Vehicle

Frank Scanzillo

EECC657

ObjectivesObjectives

Detection and avoidance of obstaclesDetection of and navigation toward light

beacon (final destination of vehicle)

SpecificationsSpecifications 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 InterfaceUser Interface

Power on/off LED status lights

– Normal operation– Target reached– Vehicle stuck

Power Switch

On

Status Lights

Off

L2Failure

L1Success

L0Normal

Microcontroller InterfacesMicrocontroller Interfaces

System block diagram

Microcontroller

Port A Port BPort AD

Sensor outputsDC motor

inputs

FL FR

Status light outputs

LSF RSF

LSR RSR

RL RR

Photo ML1 MR1

ML0 MR0

L2

L1

L0

Opto

Analytical ComponentAnalytical 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 limitsAlgorithm for system (flowchart)

Sensors UsedSensors Used

Sharp GP2Y0A21YK (4)

Sharp GP2Y0D340K (4)

Panasonic PNA4602M 38 kHz IR Photodetector

Optek OPB745 Optoreflector

Sensor ConfigurationSensor Configuration

Photo light

detector

Infrared object

proximity sensors

Infrared sensor beams

L

W

½ W

½ LSS2 SSV2

SSH2

SFV1SFV2

SV

SFH2

SF2

SS1

SF1

SFH1

SSV1

FH

SSH1

SH

FV

WO

Sensor Configuration (cont.)Sensor Configuration (cont.)

R2 = 90

04.0

7.13.52

F

FCC

I

VVR

Calculation of Sensing Calculation of Sensing Distances (front/rear)Distances (front/rear)

Stopping distance: dS = 1.3 + 0.5 cm Virtual turning radius: zero Effective turning radius:

2222 5.375.16 LWd

d = 40.97 cm )5.3797.40()( 2

121 Ldt

t = 1.74 cm Sensor body dimensions:

GP2Y0A21YK: 4.46 x 1.35 cm

Beam width:

58.8

80

6tan2 1

SFV1’ = t + dS + FV + EFV1 + ESFV1 = 1.74 + 1.3 + 1.16 + 1.71 + 1

SFV1’ = 6.91 + 1.00 cm

22222

2222 29.214.19)()( SFVFVSFHFHF ESESS

SF2 > 28.8 cm (upper bound)

22211

2111 94.445.5)()( SFVFVSFHFHF ESESS

SF1 < 7.35 cm (lower bound)

Calculation of Sensing Calculation of Sensing Distances (side)Distances (side)

Sensor body dimensions:GP2Y0D340K: 1.5 x 0.9 cm

Distance of beam vertex from vehicle: 1.5 + 0.5 cm

Photo light

detector

Infrared object

proximity sensors

Infrared sensor beams

L

W

½ W

½ LSS2 SSV2

SSH2

SFV1SFV2

SV

SFH2

SF2

SS1

SF1

SFH1

SSV1

FH

SSH1

SH

FV

WO

SH = 0.39 + 0.39 cm

SSH1 = dSS + SH + SH = 1.5 + 0.39 + 0.39

SSH1 = 2.28 + 1.00 cm

SV = 8.0 + 0.5 cm

SSV2 = L - SV + ESV + ESSV2 = 37.5 – 8 + (0.2 + 0.5) + 1

SSV2 = 31.2 + 2.0 cm222

222

222 95.92.33)()( SSHSHSSVSVS ESESS

SS2 > 34.7 cm (upper bound)

22211

2112 28.115.10)()( SSHSHSSVSVS ESESS

SS1 < 10.23 cm (lower bound)

Object size limitsObject size limits

WO = 23.5 cm (minimum width of each obstacle)

22222

222 29.2195.9)()( SFVFVSSHSHO ESESW

Photo light

detector

Infrared object

proximity sensors

Infrared sensor beams

L

W

½ W

½ LSS2 SSV2

SSH2

SFV1SFV2

SV

SFH2

SF

2

SS1

SF1

SFH1

SSV1

FH

SSH1

SH

FV

WO

System FlowchartSystem Flowchart

Current StatusCurrent 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 PlanTest Plan1. Voltage regulators

Verify that supply voltage for motors/sensors and beacon = 5 + 0.25 V Voltage regulator output (adjustable) for microcontroller = 5.3 + 0.2 V

2. Object sensors Position small object (i.e. < 1 cm wide) 5.94 + 0.20 cm from front/rear of

vehicle, aligned with the center of the front/rear bumper; verify that output > 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 38 + 2 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.)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 ConsumptionPower ConsumptionM68HC12: 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 + 100 mW photodarlington

IR Photodetector: 200 mW

Total power dissipation:

0.35 + 2(2.5) + 0.2(8) + 0.075 + 0.2 + 0.2 = 7.425 W

System CostSystem CostVendor Part Quantity Cost CE Dept. (purchased in previous course)

Optek OPB745 Optoreflector

1 N/A

“ “ “ “ “ 74LS04 Hex Inverter 1 N/A “ “ “ “ “ 74LS06 Hex Inverter

w/Open Collector 1 N/A

“ “ “ “ “ 2V Red LED 3 N/A “ “ “ “ “ Trimpot 1K

Potentiometer 1 N/A

“ “ “ “ “ Trimpot 10K Potentiometer

1 N/A

“ “ “ “ “ Jameco Breadboard 2 N/A “ “ “ “ “ LM555 Timer 1 N/A CE Dept. (loaned) Motorola

M68HC12A4EVB Evaluation Board w/interface module

1 N/A

“ “ “ Misc. resistors, capacitors, wires

N/A N/A

Toys R Us GI Joe Motorized Combat Assault Tank

1 $34.95

Radio Shack 5V DC Voltage Regulator 7805A

2 $2.98

“ “ Battery holder (2 C) 3 $4.47 “ “ Adjustable Voltage

Regulator LM317T 1 $1.99

Digikey Panasonic PNA4602M 38khz IR Photodetector

1 $3.00

“ Panasonic LN64PA 950 nm IR LED

10 $7.56

Wal-Mart Rayovac 6V Heavy Duty Lantern Battery (for beacon)

2 $5.27

CheapBatteries.com Global Instruments NiMH Battery Charger

1 $10.00

“ Global Instruments 1.2V NiMH 3800 mAH C Batteries

12 $48.00

Tri-Tech Sharp GP2Y0A21YK IR Analog Proximity Sensor

4 Free evaluation

“ Sharp GP2Y0D340K IR Digital Proximity Sensor

4 Free evaluation

Estimated total cost $118.22

Q&AQ&A