GPS Car Group

1
GPS Car Group 4

• Eric Herbert
• Daniel Gunn
• Steven Hamilton

2
Gantt Chart
3
Gantt Chart
4
Budget

• Equipment
• Wires 7.00
• MOSFET 3.50
• Diode(1) 0.50
• Capacitor(7) .70
• Inductor(1) .50
• Max639 Free
• Bread Board 4.00
• Male RS232 port 5.00
• MAX3222 1.69
• BNC to Alligators(3) 39.00
• Voltage Regulators(4) 9.74
• 12 Terminal Plug 5.00
• Batteries 9V and 9.6V with re-charger 30.00
• 
  
  106.73
• Rentals
• Remote Controlled Car 60.00 x 50 days x
  0.2 6.00
• Power Supplies(2) 500.00 x 30 days x
  0.2 30.00

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Budget

• Labor
• 9 Weeks x 14 hrs./week x 10/hr x 3
  Employees 3780.00
• Overhead
• Labor x 75 2835.00
• Equipment and Rentals 362.31
• Total 6977.31

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Power Budget
Total Current on main battery 1.259A Total
Runtime on main battery 1 Hr. 25 min. (with
1800 mAH battery) Total Current on GPS battery
60mA Total Runtime on GPS battery 8 Hr. 20
min. Total Vehicle Runtime Estimated at 1 Hr.
25 min.
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GPS Point Data 10 min
8
GPS Point Data 12 Hours
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Navigation Flowchart
Acquire GPS
Navigate
Evaluate GPS
Adjust
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Acquire GPS
Overview

• Heading - GPRMC
• 000.0 to 359.9 degrees
• Speed - GPRMC
• 0000.0 to 1851.8 knots
• Convert to meters
• Position - GPRMC
• Latitude ddmm.mmmm
• Longitude dddmm.mmmm

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Analyze Variable Overview
Total Distance
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Analyze Flowchart
Overview
New Waypoint?
Correction Angle
Heading Angle
Turn Radius
Velocity
Turn Time
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Navigate
Overview

• Servo/Turn Angle
• Correction Angle
• Proportional
• Scaled
• Turn Time
• Time Until on Course
• Waypoint
• Total Distance
• Acquire New Waypoint?
• Motor
• Scaled if Close to Finish

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Navigate

• Servo
• 1) Set Servo to Turn Angle
• 2) Center Servo after Turn Time
• Motor
• Maintain Duty Cycle
• Gradually Slow at End

Overview
Navigation Around C4 (WP1 - WP2)
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Transceiver
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Transceiver
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Servo

• 410 Hz signal which corresponds to a gt2.5 ms
  period.
• 1.1280ms pulse gave us center
• .7317ms pulse gave us left
• 1.5244ms pulse gave us right
• _at_3.3 volts we could get a 3 degree precision for
  180 degrees, however when installed in the car
  the servo didnt have enough power to over come
  friction, so we had to go with lower precision at
  5 volts.

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Chopper Schematic
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Problems (Part 1)

• Obtaining a car on time to start the project.
• Getting parts
• Getting datasheets on the parts we received
• Finding datasheets on our servo
• Getting the MSP to communicate with the computer
• Problems getting our original chopper design to
  work with the PWM signal from the MSP
• Problem getting an L298 to work according to the
  Datasheet diagrams

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Problems (Part 2)

• Problem getting transceiver to work due to a
  forgotten enable pin
• Time constraints due to previous problems
• Lack of knowledge and availability of prewritten
  code for the MSP430
• Low power modes of the MSP430
• MSP430 interrupt vectors USART routines
• TERRIBLE COMPILERS FOR MSP430!!!!!!!
• 2 Hours wasted working on navigation algorithm
  due to dead GPS batteries
• Running more than one device off of the same PWM
  clock/timer
• 8MHz resonator never worked as planned

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Algorithm/Coding Problems

• Complexity of the algorithm
• Implementing some of the math functions needed
  with our compiler
• Getting familiar with the MSP430
• Lack of development and testing time
• Stress due to other problems and time constraints
  preventing clear thinking

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Accomplishments

• Created a working chopper circuit after many
  failed prototypes
• Developed and implemented a working navigation
  algorithm
• Successfully established communication between
  35-PC GPS and MSP430
• Successfully controlled the servo
• Successfully controlled the drive motor
• Successfully controlled a combination of 35-PC
  GPS and either motor or servo but not both at the
  same time
• Assembled the car and made it look good

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How we know we are done!

• The Car goes around the parking lot unassisted.
• MSP430 Successfully Interfaces with 35-PC.
• The GPS guides the car back to its starting
  position.
• Final report is written and handed in.
• Presented to advisor.

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Our Car
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Rear View With MSP430
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Rear View Without MSP430
18v Socket for GPS
Switch for Motor
Quick Disconnect for MSP430
Main Power Switch
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Side View Cover Off
5v regulator for servo
2 9v batteries for GPS
3.3v regulator for MSP430
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Chopper Circuit
Mosfet Heatsink
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References

• Paul Herbert
• Chris Cowden
• Dr. Richard Potter
• Garmin 35-PC Technical Specifications
• Hofmann-Wellenhof
• GPS Theory and Practice 5th Edition
• Stefan
• Navigating with GPS
• Bruch, Gilbreath, Muelhauser, Lum
• Accurate Waypoint Navigation Using
  Non-Differential GPS

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Questions?