F12: Self-Driving GPS Following Car

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Self-Driving GPS Following Car

Abstract

The objective of this project is to create an autonomous vehicle that follows another car. A leading car will continually inform the autonomous car of its location. The autonomous car will then drive to the target location while avoiding obstacles along the way.

Introduction and Objectives

The Self-Driving GPS Following Car follows another car by driving to the GPS coordinates of the leading car. A ZigBee communication link transmits the GPS data from the leading car to the following car. The following car utilizes a GPS and a compass to determine its own location and orientation relative to magnetic north. Using the two pairs of GPS coordinates and the orientation of the car, the bearing and distance necessary to be traveled is calculated. The car uses proximity sensors, so the car can avoid obstacles while navigating to the destination.

The project required the following objectives to be accomplished:

  • Read GPS coordinates of the leading car and the following self-driving car
  • Use XBee modules to send and receive GPS coordinates from the leading car to the following car
  • Compute the true north bearing and distance necessary for the following car to reach the leading car
  • Account for difference between true north and magnetic north in bearing calculation
  • Read the magnetic north bearing using a compass
  • Read the distance to objects using proximity sensors
  • Control steering motor to steer left, right, and straight using a motor controller
  • Control direction motor to move forward, backward, and stop using a motor controller
  • Determine algorithm to drive toward destination
  • Determine algorithm to avoid obstacles

Team Members and Responsibilities

  • Elias Barboza
    • PWM driver, motor controllers, and obstacle avoidance
  • Caleb Chow
    • Read compass, read GPS coordinates, and move toward target GPS coordinates
  • Stephen Lu
    • ADC driver, read proximity sensors, compute distance based on measurement, and obstacle avoidance

Schedule

Week Number Scheduled Items Actual

Week 1: Design
(October 29)

  • Order Parts
  • Design proximity sensors placement
  • Design algorithm to avoid obstacles
  • Design algorithm to move toward GPS coordinate
    using compass
  • Parts all obtained
  • Proximity sensor and algorithm design completed

Week 2: Construction
(November 5)

  • Upgrade leading car with microcontroller, XBee, GPS,
    and a battery pack
  • Upgrade following car with microcontroller, XBee, GPS,
    compass, proximity sensors, motor controllers, and a
    battery pack
  • Read GPS information by connecting GPS to Xbee
  • Leading car upgrade completed
  • Following car upgrade completed
  • GPS information sent to Xbee completed

Week 3: Drivers
(November 12)

  • Develop curve-fit function for proximity sensors
  • Read direction from compass
  • Enable car driving capabilities / motor controllers
  • Send / receive data using XBee modules
  • Proximity sensors completed
  • Compass direction completed
  • Motor controllers completed
  • Send / receive data using XBee modules done

Week 4: Coding
(November 19)

  • Code obstacle avoidance
  • Completed

Week 5: Coding
(November 26)

  • Code moving toward GPS coordinate
  • In progress

Week 6: Testing
(December 3)

  • Testing

Week 7: Finalization
(December 10)

  • Make final changes for demo
  • Finalize content in Wiki article

Parts List & Cost

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Parts Quantity Cost Link

RC Car -
Beetle RC Car

2

$25

Previously owned


GPS -
GlobalSat ET-318

2

$37.21

GPS DataSheet

XBee Module -
XBee 1mW Chip Antenna

2

$24.95

Xbee Module

Motor Controller -
5A Motor Controller

2

$17.99

Motor Controller

Compass -
LSM303DLM

1

$14.95

Compass

Sonar Range Finder -
LV-MaxSonar-EZ4

2

$26.95

Sonar Range Finder

Ultrasonic Range Finder -
SRF08

1

~$50

Ultrasonic Range Finder

Microcontroller -
2012 SJ One Board

1

~$120

SJ One Board

Design & Implementation

Hardware Design The leading car consists of the following additional hardware:

  • XBee module
  • GPS module
  • 3.3V regulator circuit

The leading car is responsible for sending its GPS coordinates to the following car. This is accomplished by sending the raw GPS data over ZigBee to the following car. The GPS and XBee modules both use UART to communicate, so no microcontroller is necessary. The paired XBee modules will take care of the data transfer. Both modules ran off the same 3.3V power supply, which came from a regulator off of the car’s battery pack.

File:CmpE146 F12 T7 Leading Car Block Diagram.png

Hardware Design

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Hardware Interface

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Leading Car

Cmpe146 F12 T7 Leading Car Block Diagram.png

Leading Car Block Diagram

  • GPS – UART
    • Outputs GPS data on Tx to XBee Rx
  • XBee – UART
    • Inputs data to send on Rx from GPS Tx
  • Power Supply – 3.3V
    • Supply power to GPS and XBee modules
    • Add 3.3V voltage regulator with filtering capacitors to RC car’s battery pack

Following Car

Cmpe146 F12 T7 Following Car Block Diagram.png

Following Car Block Diagram

  • Microcontroller
    • 2012 SJSU One Board (LPC1758)
  • GPS – UART
    • P2.8 = Tx, P2.9 = Rx
    • PINSEL4 = 0b10 for both
  • Xbee – UART3
    • P4.28 = Tx, P4.29 = Rx
    • PINSEL9 = 0b11 for both
  • I2C2 Devices
    • P0.10 = SDA, P0.11 = SCL
      PINSEL0 = 0b10 for both
    • Components :
      Proximity sensor (SRF08)
      Compass
  • Proximity Sensors (LV-MaxSonar-EZ4) – ADC4 and ADC5
    • P1.30 = AD0.4
    • P1.31 = AD0.5
    • PINSEL3 = 11 for both
  • Motor Controllers (2) – PWM
    • P1.20 = PWM1.2
    • P1.24 = PWM1.5
    • PINSEL3 = 10 for both
  • Power Supply – 5.0V from RC car's original battery pack
    • Supply power to motor controllers for motors
    • Supply power to SRF08 proximity sensor
  • Power Supply – 3.3V
    • Microcontroller 3.3V output
    • Supply power to GPS, Xbee, and LV-MaxSonar-EZ4 proximity sensors

Software Design

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Implementation

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Testing & Technical Challenges

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Wifi Connection Issues

Many wifi connection issues were encountered. To solve this problem, a dedicated task was created to re-connect to wifi if the connection was ever lost.

Conclusion

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Project Video

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Project Source Code

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References

Acknowledgement

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References Used

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Appendix

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