Transcript Obstacle Avoidance Vehicle

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
Photo
light
Light
detector detector
stand
Tank
IR beacon
(target)
18 cm
Infrared
object
sensors
Optoreflector
1 cm 7 cm
Obstacle
25
cm
User Interface

Power on/off
 LED status lights
On
L2
L1
L0
Failure Success Normal
– Normal operation
– Target reached
– Vehicle stuck
Off
Power
Switch
Status Lights
Microcontroller Interfaces
Microcontroller
Port A
Port AD
Port B
Opto
L2
FL
FR
Photo
ML1
MR1
ML0
MR0
L1
LSF
LSR
RL
RSF
RSR
L0
RR
Sensor outputs
Status light
outputs
System block diagram
DC motor
inputs
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
W
DFH
SFH
Infrared
object
proximity
sensors
Photo
light
detector
Infrared
sensor
beams
2
SF
2
SF
1
SS
L
½L
SS
2
SSV
1
DSH
2
SSV
1
SFV
2
DFV
SFV
1
SSH
SSH
1
½
W
2
SFH
1
WO
DSV
Sensor Configuration (cont.)
R2 
VCC  VF 5.3  1.7

IF
0.04
R2 = 90 W
Calculation of Sensing
Distances (front/rear)



Stopping distance: dS = 1.3 + 0.5 cm
Virtual turning radius: zero
Effective turning radius:
d  W 2  L2  16.52  37.52
d = 40.97 cm
t  12 (d  L)  12 (40.97  37.5)
t = 1.74 cm

Sensor body dimensions:
GP2Y0A21YK: 4.46 x 1.35 cm

Beam width:
 6
  2 tan1    8.58
 80 
SFV1’ = t + dS + DFV + EFV1 + ESFV1 = 1.74 + 1.3 + 1.16 + 1.71 + 1
SFV1’ = 6.91 + 1.00 cm
S F 2  ( S FH 2  E SFH 2 ) 2  ( S FV 2  E SFV 2 ) 2  19.4 2  21.29 2
SF2 > 28.8 cm (upper bound)
S F 1  ( S FH1  E SFH 1 ) 2  ( S FV 1  E SFV 1 ) 2  5.45 2  4.94 2
SF1 < 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:
1.5 + 0.5 cm
W
DFH
SFH
Infrared
object
proximity
sensors
Photo
light
detector
SF
2
DSH = 0.39 + 0.39 cm
SF
SSH1 = dSS + DSH + EDSH = 1.5 + 0.39 + 0.39
SSH1 = 2.28 + 1.00 cm
DSV = 8.0 + 0.5 cm
Infrared
sensor
beams
2
1
SS
L
½L
SS
2
SSV
1
DSH
2
SSV
SSV2 = L - DSV + ESV + ESSV2 = 37.5 – 8 + (0.2 + 0.5) + 1
1
SSV2 = 31.2 + 2.0 cm
S S 2  ( S SV 2  E SSV 2 ) 2  ( S SH 2  E SSH 2 ) 2  33.2 2  9.95 2
SS2 > 34.7 cm (upper bound)
S S 2  ( S SV 1  E SSV 1 ) 2  ( S SH 1  E SSH 1 ) 2  10.15 2  1.28 2
SS1 < 10.23 cm (lower bound)
SFV
2
DFV
SFV
1
SSH
SSH
1
½
W
2
SFH
1
WO
DSV
Object size limits
DFH
SFH
Infrared
W
object
proximity
sensors
Photo
light
detector
Infrared
sensor
beams
2
SF
2
WO  ( S SH 2  E SSH 2 )  ( S FV 2  E SFV 2 )  9.95  21.29
2
2
2
WO = 23.5 cm (minimum width of each obstacle)
SF
2
1
SS
L
½L
SS
2
SSV
1
DSH
2
SSV
1
SFV
2
DFV
SFV
1
SSH
SSH
1
½
W
2
SFH
1
WO
DSV
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.
2.
3.
4.
5.
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
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.
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.
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.
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 + 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 Cost
Vendor
CE Dept. (purchased
in previous course)
“““““
“““““
“““““
“““““
“““““
“““““
“““““
CE Dept. (loaned)
“““
Toys R Us
Radio Shack
““
““
Digikey
“
Wal-Mart
CheapBatteries.com
“
Tri-Tech
“
Part
Optek OPB745
Optoreflector
74LS04 Hex Inverter
74LS06 Hex Inverter
w/Open Collector
2V Red LED
Trimpot 1K
Potentiometer
Trimpot 10K
Potentiometer
Jameco Breadboard
LM555 Timer
Motorola
M68HC12A4EVB
Evaluation Board
w/interface module
Misc. resistors,
capacitors, wires
GI Joe Motorized
Combat Assault Tank
5V DC Voltage
Regulator 7805A
Battery holder (2 C)
Adjustable Voltage
Regulator LM317T
Panasonic
PNA4602M 38khz IR
Photodetector
Panasonic LN64PA
950 nm IR LED
Rayovac 6V Heavy
Duty Lantern Battery
(for beacon)
Global Instruments
NiMH Battery
Charger
Global Instruments
1.2V NiMH 3800
mAH C Batteries
Sharp GP2Y0A21YK
IR Analog Proximity
Sensor
Sharp GP2Y0D340K
IR Digital Proximity
Sensor
Estimated total cost
Quantity
1
Cost
N/A
1
1
N/A
N/A
3
1
N/A
N/A
1
N/A
2
1
1
N/A
N/A
N/A
N/A
N/A
1
$34.95
2
$2.98
3
1
$4.47
$1.99
1
$3.00
10
$7.56
2
$5.27
1
$10.00
12
$48.00
4
Free evaluation
4
Free evaluation
$118.22
Q&A