Project Summary

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http//cegt201.bradley.edu/projects/proj2001/gpsca
rjb/
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Presentation Overview

• Project Summary
• Project Goals
• What is GPS?
• Block Diagram
• Project Subsystems
• Hardware Components
• System Inputs
• Software Functionality
• Timeline
• Final Results
• Cost Analysis

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Project Summary
The goal of this project is to design and build a
vehicle that will be able to navigate from one
location on Bradley University's campus to
another along the sidewalks without human
intervention.  In order to do this we have
decided to implement a global positioning system
(GPS) as the means by which the vehicle will know
its position. Heading from a digital compass
will be used in conjunction with position
information from the GPS receiver to steer the
vehicle.
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Project Goals

• Integrate a control system on a self-propelled
  vehicle utilizing GPS
• Implement all controls using a low-cost
  microprocessor and GPS receiver

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WHAT IS GPS?
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GDOP (Geometric Dilution Of Precision)
Components PDOP Position Dilution
of Precision (3-D). HDOP Horizontal
Dilution of Precision (Latitude, Longitude).
VDOP Vertical Dilution of Precision
(Height). TDOP Time Dilution of
Precision (Time). .
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Sample of DGPS data
Horizontal Standard Deviation 104.9 meters
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Sample of DGPS data
Horizontal Standard Deviation 2.3 meters
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GPS Module

• Problems With Differential GPS
• Accuracy was not improved, and sometimes even
  reduced
• Correction signal is transmitted over a range
  that adds error. ( 1m error for every 100 km (62
  miles) )
• Maximum broadcast range 450 km (280 miles)
• Signal latency can be as great as 3 to 5 seconds
• Correction signal and receiver signal are
  determined by different clusters

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The Solution

• Dead-Reckoning
• Uses a digital compass to account for the errors
  of GPS.
• Normally used while satellites are not visible.
• We are incorporating this concept by using the
  compass to control the steering.

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Digital Compass

• 2 degree accuracy, 1 degree resolution
• 5Hz sampling rate (software down-sampled to 1Hz)
• Pin selectable BCD or binary output format
• Power supply single 5 volt
• Size 1.5"l x 1.3"W x 0.4"H
• Weight 0.2 lbs.

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Main Project Breakdown

• Components
• Power Circuitry
• Steering control / Linear Actuator
• Drive Motors
• Subsystems
• Digital compass
• GPS
• Software
• Autonomous mode
• Diagnostic mode

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Block Diagram
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Disciplines Involved

• Power electronics
• Microprocessor controlled feedback systems
• DC Motors
• GPS and Differential GPS
• RF related interferences
• Cross compilers using Assembly and C-code

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Hardware Components

• Steering and Drive circuitry

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Drive Circuitry

• Optically Isolated
• 12 Volt Bias Supply
• Drives Two Motors In Series
• Delivers 40 Amps Max Current
• Pulse Width Modulated Control Signal

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Drive Circuitry
12v
12v
5v
12v
12v
30
Voltage Spike
13V
25V
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Steering Circuitry

• H-Bridge Integrated Motor Controller
• includes
• Bi-directional input control
• Brake Control
• PWM input
• Linear Actuator Attached To The Steering Rod
• PWM Controlled Rate of Change
• Potentiometer Feedback Position Control

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Steering Circuitry
PWM
10nF
5
V
5
11
Dir
3
10
Brake
Feedback
12
V
4
6
7
LMD18200T
10nF
2
1
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GPS

• Ashtech G8
• Compact OEM GPS Module

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GPS Module

• Completed
• Serial Communication between EMAC and G8
• Data acquisition using GPS and DGPS
• Acquiring position information

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Summary of GPS Results

• Accuracy varying from 5m to 50m
• GPS Heading and velocity accurate only at gt2.5
  mph.
• Accurate position requires up to four hours of
  stationary data acquisition.

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Digital Compass Schematic
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Software Control

• Using C-code cross-compiler
• in Keil programming environment for 8051

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Software System Description

• Steering Control
• Sends control signal to actuator to steer towards
  the desired heading.
• Limited to 5 mm of actuator movement per 1 second
  cycle. (About 3 deg.)

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Software System Description

• Drive Control
• Begins with an 40 (fast) duty cycle to overcome
  initial vehicle inertia.
• Maintains a constant duty cycle of 30 (slow) at
  100Hz over the course of travel to the motors
  giving a speed of approximately 1 mph.

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Software Function

• Modes of Operation
• Diagnostic Mode
• 2 Speed Controls
• (fast) and (slow)
• Manual Steering Controls Through the 80535
• left and right (5 mm actuator increments)
• Autonomous Mode
• Automatic Speed Control
• larger duty cycle to overcome inertia, then
  slower velocity
• Automatic Steering Control
• based on digital compass error signal
• Automatic Break With GPS Coordinates

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Project Timeline
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Final Results
MPEG of vehicle driving, and stopping
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Electronics
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GPS Sensor
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Antenna
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Actuator
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Cost Analysis
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Special Thanks To

• Dr. Brian Huggins
• Advisor, Customer, and technical writing editor
• Dr. In Soo Ahn
• Advisor/GPS expert
• Mr. Chris Mattus
• EMAC guru, connection specialist (and photo
  editor)
• Nick Schmidt
• The do-it-all man
• Prof. Steve Gustchlag
• Power genius
• Dr. Gary Dempsey
• Cross-Compiler Master

And finally...
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• For their support and sponsorship
  of the GPS-Guided Autonomous Vehicle
  

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ANY QUESTIONS?
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