Transcript Sophomore Design Class Automated Highway Simulation

Sophomore Design Class
Automated Highway Simulation
Group 2:
Jeremy Sletten
Patrick Murphy
Michael Olson
Randa Ibrahim
Purpose
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The purpose of this course was to create a
line-following car that simulates the operation
of an automated highway system. This
vehicle would then be used as the design
model for a sophomore design class.
Project Constraints
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Total price for the car must be under $200,
assuming bulk orders for most items.
Because this car was to be designed in the
sophomore design course, all subsystems
had to be designed on a level that is known
to, or can easily be taught to sophomore
level students.
Top Level Car Design
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We decided to build our own car from the
ground up, instead of taking a pre built R/C
car and modifying the controls for speed and
steering.
Justification:
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Less expensive to purchase in bulk
Easier and more cost effective to manufacture
Micro-controller Board
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We chose the Axiom CML-9S12DP256 .
Justification:
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Availability
Currently in use at OU for various CSE courses
Image Craft C compiler
Chassis
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Made from lightweight
aluminum
Easy to assemble
All screw holes and slots
would be pre drilled
Negligible cost
Manufactured here at OU
Had to modify our design
late in the project.
Final Chassis Design
•The original tracks
created too much
tension on the motors
•The chassis was
redesigned to drive
solely from the wheels
on the motors
•A third, center-mounted
pivoting castor was
added to improve
support, without causing
drag when turning
H-Bridge
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Had a lot of problems getting
pre-built H-Bridges with the
appropriate surface mounts.
Resorted to building our own
H-Bridge out of transistors.
Due to the power
requirements of the motors,
an additional circuit was
made to amplify the PWM
signal coming from the
68HC12 to have a peek
voltage capable of
controlling the H-Bridge
setup.
H-Bridge – 2nd Design
Motors
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Performed some basic calculations based on
the total weight of our vehicle and a frictional
coefficient of .9 (Rubber on Pavement)
Reviewed a variety of motors made available
to us and found one that met the minimum
calculated torque requirements.
Sensors
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Sharp GP2Y0A02YK
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Long range
Allows us to slow down or
even stop to avoid another
vehicle or obstacle in the
road.
Fairchild QRB1134
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Better detection range
Currently using a 3 sensor
array to follow the line,
however the number of
sensors used could be
increased to give smoother
turning and line detection.
Software
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Simple implementation
Takes 4 inputs from the sensors (1 distance
and 3 line following)
Sets the PWM output duty cycle accordingly.
Software
Flow Chart
Software Flowchart cont.
Line Following Algorithm
Vehicle State Operation
Straight
010
Continue on
in normal
operation.
Line Following Algorithm
Vehicle State Operation
A little to the
left
011
Turn slightly
to the right
Line Following Algorithm
Vehicle State Operation
A lot to the
left
001
Turn more
to the right
Line Following Algorithm
Vehicle State
Operation
Off the track to
either the left
or right
000
Check against
previous state
to see which
side the car is
off of. Turn
back hard in
the opposite
direction.
Line Following Algorithm
Cost Considerations
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Microcontroller - Axiom CML-9S12DP256 - $115
Motors - $4-ea. X 2 motors = $8
Distance Sensor - $12.50
Line Following Sensor - $2-ea. X 3 sensors = $6
NS LMD18200 H-bridges X 2 = $18
Misc. transistors and resistors - $5
Getting the manufactured materials at a negligible
cost and free labor…
Cost Considerations – Cont.
Priceless!!!
Cost Considerations – Cont.
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Total Cost ~ $164.50
Future considerations for remaining balance
could be left up to the students.
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Higher powered motors (Faster car)
Additional sensors (More accurate turning)
Higher powered battery packs (Longer run time)
Paint / Body Kits (More aesthetically pleasing)
Development Issues
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H-Bridges took a long time to come in and set our
timelines back a lot further then we were comfortable
with. Made motor testing impossible until very late in
the design.
Hard to determine total vehicle weight early on,
ended up with high rpm motors bordering on
insufficient torque.
Due to the problems involving the Motors / H-Bridge
our original design for a tracked vehicle had to be
modified.
Questions ? ? ?
The End