Sophomore Design Class Automated Highway Simulation

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Sophomore Design ClassAutomated Highway
Simulation

• Group 2
• Jeremy Sletten
• Patrick Murphy
• Michael Olson
• Randa Ibrahim

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Purpose

• 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.

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Project Constraints

• 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.

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Top Level Car Design

• 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
• Less expensive to purchase in bulk
• Easier and more cost effective to manufacture

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Micro-controller Board

• We chose the Axiom CML-9S12DP256 .
• Justification
• Availability
• Currently in use at OU for various CSE courses
• Image Craft C compiler

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Chassis

• 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.

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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

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H-Bridge

• 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.

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H-Bridge 2nd Design
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Motors

• 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.

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Sensors

• Sharp GP2Y0A02YK
• Long range
• Allows us to slow down or even stop to avoid
  another vehicle or obstacle in the road.
• Fairchild QRB1134
• 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.

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Software

• Simple implementation
• Takes 4 inputs from the sensors (1 distance and 3
  line following)
• Sets the PWM output duty cycle accordingly.

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SoftwareFlow Chart
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Software Flowchart cont.
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Line Following Algorithm
Vehicle State Operation
Straight 0 1 0 Continue on in normal operation.
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Line Following Algorithm
Vehicle State Operation
A little to the left 0 1 1 Turn slightly to the right
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Line Following Algorithm
Vehicle State Operation
A lot to the left 0 0 1 Turn more to the right
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Line Following Algorithm
Vehicle State Operation
Off the track to either the left or right 0 0 0 Check against previous state to see which side the car is off of. Turn back hard in the opposite direction.
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Line Following Algorithm
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Cost Considerations

• 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

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Cost Considerations Cont.

• Priceless!!!

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Cost Considerations Cont.

• Total Cost 164.50
• Future considerations for remaining balance could
  be left up to the students.
• Higher powered motors (Faster car)
• Additional sensors (More accurate turning)
• Higher powered battery packs (Longer run time)
• Paint / Body Kits (More aesthetically pleasing)

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Development Issues

• 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.

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Questions ? ? ?

• The End