F12: 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	Planned Items	Actual Items
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	Ordered parts Designed proximity sensor placement Designed obstacle avoidance algorithm Designed move to destination GPS algorithm
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 coordinate from GPS module	Tested proximity sensors Finished ADC and PWM drivers Paired XBee modules Read GPS coordinates and computed required bearing and distance to travel to destination
Week 3: Drivers (November 12)	Read direction from compass Enable car driving capabilities / motor controllers Send / receive data using XBee modules	Motors controllers fully interfaced Mounted proximity sensors, motor controllers, microcontroller, and GPS Created upgrade module for leading car
Week 4: Coding (November 19)	Code obstacle avoidance	Tested obstacle avoidance Sent GPS data from leading car to following car Swapped to non-tilt compensated compass Mounted compass Restructure and reorganize code
Week 5: Coding (November 26)	Code moving toward GPS coordinate	Tested obstacle avoidance Swapped a proximity sensor to unify sensors Swapped to less power hungry motor controllers New motor controllers fully interfaced Upgraded to use 5xAA battery pack Rewired parts with finalized placement
Week 6: Testing (December 3)	Testing	Tested obstacle avoidance Tested move to GPS coordinate
Week 7: Finalization (December 10)	Make final changes for demo Finalize content in Wiki article	Tested move to GPS coordinate

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.

Hardware Design

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Hardware Interface

In this section, you can describe how your hardware communicates, such as which BUSes used. You can discuss your driver implementation here, such that the Software Design section is isolated to talk about high level workings rather than inner working of your project.
Leading Car

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

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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