Sophomore Design ClassAutomated Highway Simulation

Group 2:Jeremy SlettenPatrick MurphyMichael OlsonRanda Ibrahim

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.

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.

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

Micro-controller Board

We chose the Axiom CML-9S12DP256 . Justification:

– Availability– Currently in use at OU for various CSE courses– Image Craft C compiler

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.

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

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

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

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.

Software

Simple implementation Takes 4 inputs from the sensors (1 distance

and 3 line following) Sets the PWM output duty cycle accordingly.

SoftwareFlow Chart

Software Flowchart cont.

Line Following Algorithm

Vehicle State Operation

Straight

0 1 0

Continue on in normal operation.

Line Following Algorithm

Vehicle State Operation

A little to the left

0 1 1

Turn slightly to the right

Line Following Algorithm

Vehicle State Operation

A lot to the left

0 0 1

Turn more to the right

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.

Line Following Algorithm

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…

Cost Considerations – Cont.

Priceless!!!

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)

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.

Questions ? ? ?

The End