GPS-Guided Autonomous Vehicle

GPS-Guided Autonomous Vehicle

http://cegt201.bradley.edu/projects/proj2001/gpscarjb/


Presentation Overview

• Project Summary• Project Goals• What is GPS? • Block Diagram• Project Subsystems

– Hardware Components– System Inputs– Software Functionality

• Timeline• Final Results• Cost Analysis


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.


Project Goals

• Integrate a control system on a self-propelled vehicle utilizing GPS

• Implement all controls using a low-cost microprocessor and GPS receiver

WHAT IS GPS?

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). .


Sample of DGPS data

Horizontal

Standard

Deviation :

104.9 meters


Sample of DGPS data

Horizontal

Standard

Deviation :

2.3 meters


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


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.


• 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.

Digital Compass


Main Project Breakdown

• Components– Power Circuitry

• Steering control / Linear Actuator

• Drive Motors

• Subsystems– Digital compass– GPS

• Software – Autonomous mode– Diagnostic mode


Block Diagram

GPS Signal

Potentiometer Feedback

LMD18200(H-Bridge)

PowerCircuitry

Drive Motor

Linear Actuator

GPS Receiver

EMACBoard

Battery 1

Keypad

LCD Display

Digital Compass

Battery 2


Disciplines Involved

• Power electronics

• Microprocessor controlled feedback systems

• DC Motors

• GPS and Differential GPS– RF related interferences

• Cross compilers using Assembly and C-code


Hardware Components

Steering and Drive circuitry


Drive Circuitry

•Optically Isolated

•12 Volt Bias Supply

•Drives Two Motors In Series

•Delivers 40 Amps Max Current

•Pulse Width Modulated Control Signal


Drive Circuitry

+5v+12v

+12v

+12v

From the P

+12v


Voltage Spike

13V

25V


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


Steering Circuitry

+12V

+5V

1

2

3

4

5

6

7

10

11L

MD

1820

0T

10nF

10nF

Dir

Brake

PWM

Feedback


Steering

Drive


GPS

Ashtech G8

Compact OEM GPS Module


GPS Module

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


Summary of GPS Results

• Accuracy varying from 5m to 50m

• GPS Heading and velocity accurate only at >2.5 mph.

• Accurate position requires up to four hours of stationary data acquisition.


Digital Compass Schematic

5V regulated

ground

P4.3

P1.7

P1.4

ground

5V regulated

ground

P4.4


Software Control

Using C-code cross-compiler

in Keil programming environment for 8051


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.)


• 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.

Software System Description


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


SEM_WEEK ACCOMPLISHED1_1 Component Reasearch1_2 Component Selection1_3 Acuator Testing / GPS Research1_4 GPS Research

winter break Actuator Design / GPS Testing / Code Building2_1 Code Building / GPS Testing / Actutor Testing2_2 Actuator Mount / GPS Testing / Code Building2_3 GPS Testing / Code Building2_4 Drive Circuitry Design and Testing2_5 Differential GPS Testing / Drive Circuitry2_6 Final Code for GPS and Circuit Assembly2_7 DGPS Testing within Sytem2_8 Digital Compass Interrupt / Code Rebuilding2_9 Digital Compass Testing and Implementation2_10 Code Debugging / Vehicle Testing2_11 Code Debugging / Vehicle Testing Outside2_12 Student Expo / Final Testing

Project Timeline


Final Results

MPEG of vehicle driving, and stopping



Electronics


GPS Sensor


Antenna


Actuator


Cost Analysis

Part CostJameco Digital Compass $44.95Peg Perego Gauch Grande $399.99EMAC 80535 $379.95G8 GPS Receiver incl. Evaluation kit $475.00 (without evalution kit) [$98.00]Linear Actuator $95.00H-Bridge $20.00IRFP240 (2) drive circuit $8.02Additional passive/active components $10.00

Total Cost $1,432.91[total cost with OEM module, not evaluation kit] $1,055.91


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...


•

– For their support and sponsorship of the GPS-Guided Autonomous Vehicle


ANY QUESTIONS?


Documents

GPS-Guided Autonomous Vehicle