Download Homing Tank with Obstacle Avoidance

Homing Tank with Obstacle
Avoidance (HToA)
Seth “The Assembler” Hill
Jason “The Electrician” Brue
Project Objectives

Tank will move towards and find an
infrared emitting beacon



The tank will be positioned anywhere within
the emitting radius of the beacon
Once underway, the tank will stop
periodically to adjust steering
The tank will stop once crossing a reflective
tape circle around the emitter
Project Objectives (cont.)

Tank will avoid obstacles


If a obstacle is perceived, the tank will stop
immediately and move around it
Once the obstacle has been successfully
navigated, the tank will continue towards the
infrared beacon
Project Specifications

Beacon



Will transmit infrared signal equally within its 360º
radius
Vehicle must be placed within an 11 meter radius of
the beacon
Obstacles



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Must be shorter than infrared emitters/receiver
Must not be concave
Must be as high or higher than the ultrasonic sensor
Cannot be dynamically placed once vehicle homing
has begun
Project Specifications (cont.)

Tank


Must have a turning radius of close to 0
Must be large enough to hold all on-board
components






HC12
Servomotor
Ultrasonic sensor
IR receiver
Opto-reflector
Power supplies
Project Specifications (cont.)

Miscellaneous




There shall be no other infrared emitting
devices within range of the receiver
There shall be no other ultrasonic emitting
devices within range of the vehicle
There shall be no reflective surfaces, other
than the tape, in the path of the vehicle.
There shall be a 2 foot radius between the
reflective tape ring and the infrared beacon
Project Specifications (cont.)

User interface

Input
On/Off Switch
Start Switch
Debug Switch

Output
Done
Avoid /
Search
Reflective tape
sensed
IrDA received
strength
+5
Volts
Debugging LEDs
Motor
1 On
Motor
2 On
Random Analytical Facts



Height of infrared emitters: 70cm
Radius between infrared beacon and reflective
tape: .5m
Tank footprint: 410mm Length
150mm Width



Turning radius: 13.29mm
Ultrasonic sensing range > 13.29mm + stopping
distance of tank motors (tbd)
Lost productivity due to spam per employee
per year: $874
Vehicle Control Algorithm
Background loop:
Output status to LEDs
Goto Background loop
Timer interrupt:
Stop vehicle
Sense beacon
Adjust steering accordingly
Move “forward”
Obstacle interrupt:
Stop vehicle
If obstacle bit = ‘0’ then
Rotate vehicle 90 clockwise
Rotate ultrasonic sensor 90 counterclockwise
Set obstacle bit = ‘1’
Endif
Move forward
No Obstacle Interrupt:
If obstacle bit = ‘1’ then
Stop vehicle
Rotate vehicle 90 counterclockwise
Rotate ultrasonic sensor 90 clockwise
Move “forward”
Endif
Division of Work

Seth



HC12 assembly coding
Ultrasonic sensor testing
and integration
Reflective sensor testing
and integration
 Both
 System testing
 Paperwork
 Everything!

Jason




Beacon design and
construction
Beacon testing
Tank motor testing and
integration with HBridge circuit
Servomotor testing and
integration
Work Completed – System Block
Design
HC12
Port A
Switches
Port B
LED’s
Port T
Photo
Reflector
Port P
Port A/D
Servo
motor
IR
Receiver
H Bridge
US Drive
Circuit
Ultrasonic
Sensor
DC
Motor1
DC
Motor 2
Work Completed – Infrared
Beacon
Work Completed – Infrared
Beacon (cont.)


Timer must
produce 38
KHz square
wave with
50% duty
cycle for
infrared
emitters
Each infrared
emitter
requires 60 mA
of current for
proper
operation
Work To Be Completed (uh….)

Parts acquisition



Construction


Integration of all components with tank body
Coding


Tank body has been chosen but has yet to arrive
Ultrasonic sensor has been rethought due to price constraints
Everything
Testing





Beacon range and signal strength consistency
Servomotor
Ultrasound sensor
Opto-reflector
H-Bridge and Tank motors
Test Plan




Test individual components once they arrive for
output voltage and current range
Integrate individual components and circuits
together and insure proper operation
Integrate HC12 with all other components and
write basic subroutines to ensure that
microcontroller is interpreting inputs correctly
Implement controller algorithm as described
previously
Test Plan – Controller Algorithm

Write assembly incrementally with each
new section observing and reacting to new
input(s)

Implement interfaces with:
1)
2)
3)
4)
5)
tank motors
Implement interface with opto-reflector
Implement interface with servomotor
Implement interface with infrared detector
Implement interface with ultrasonic sensor
Test Plan – Final Stage

Once tank “appears to” be behaving “correctly”

Put tank in many different situations to ensure
robustness of reaction




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
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Distance from emitter
Number of obstacles
Placement of obstacles
Types of obstacles
Orientation of obstacles
Beginning orientation of tank
And anything else we can think of!

Any suggestions?
Power Consumption - Beacon
Part
Infrared Emitters
Power Consumption
60mA  1.4V  6 = 504mW
5 resistor
120mA2  5 = 72mW
555 timer
613mW
5 k and 1 k resistors < 10mW
 Total:
1.2 Watts


Power supplied – 18 Wh through 4 D-cell
batteries
Therefore, one can expect to run the
beacon continuously for 15 hours before a
change of batteries is needed
Power Consumption - Tank
Part
Power Consumption
servomotor
6V * 8 mA = 48 mW
68HC12
225 mW
infrared receiver
200 mW
DC motors
unknown
H-Bridge
unknown
LEDs
9 * 60mW = 540 mW
phototransistor
100 mW
Total:
1.11W + unknowns

Until tank arrives, power requirements for DC motors are unknown



However, they will add a significant power requirement
Tank will be powered by a rechargeable 7.2V battery pack
Ultrasonic sensor has been rethought, and thus its power requirements
are unknown

Although a major power requirement, it will be powered separately
from the rest of the tank to ensure proper operation
System Cost
Name
Vendor
Remote Control Tank Kit
Collectorsfield dba Jungletoy
Servomotor
hvw tech
Ultrasonic sensor
tbd
Infrared receiver(s)
digikey
Infrared emitter(s)
digikey
Phototransistor(s)
digikey
Opto-isolator
digikey
voltage regulators
digikey
heat sinks
digikey
transistors
digikey
h-bridge
hvw tech
68HC12 evaluation board
Motorola
various electronic components
Radioshack
various mechanical components
Home Depot
Cost Amount Paid
69.99
69.99
18.95
18.95
tbd
tbd
4.29
4.29
2.98
2.98
10.83
10.83
4.45
4.45
5
5
3
3
5
5
16.95
16.95
98.83
free
5
5
20
20
Total 166.44 + tbd
Safety Concerns



Some high powered devices onboard system
could present shock hazard
During demo, moving tank may create traffic
congestion and possible pedestrian accident
within the halls of the computer engineering
building
Falling infrared beacon may injure feet (please
wear steel-shoed boots on demo day)