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GEM UNIT Autonomous GEM Vehicle


GEM UNIT Autonomous GEM Vehicle – PowerPoint PPT presentation

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Title: GEM UNIT Autonomous GEM Vehicle

GEM UNIT! Autonomous GEM Vehicle
  • Adrian Afan
  • Thomas Fong
  • Martin Lizarde Jr.
  • Zaynal Pham
  • June 2nd, 2005

  • Objective
  • to modify a neighborhood electric vehicle (GEM)
    to autonomously move from one location to another
    while detecting and avoiding objects along the
  • the GEM can be manually controlled via a joystick
    in a drive-by-wire configuration
  • when the desired location is reached, the GEM
    will park itself in a designated parking spot

Introduction (Continued)
  • Approach
  • the GEM is guided using x and y mapping via
    Global Positioning System (GPS) and uses a laser
    range finder to detect and avoid obstacles
  • parking will be implemented by utilizing a
    specifically designed object that the vehicle
    will detect and use as a reference point to align
    and park directly in front of
  • The joystick is interfaced to a microcontroller
    to control the vehicle manually

Introduction (Continued)
  • The microcontroller will be used to control the
    throttle, braking, steering based on the input
    from the joystick
  • The master controller (laptop) will be used for
    more demanding applications and processing such
    as communication with the GPS, laser range
    finder, digital compass
  • It processes the data to find the desired heading
    of the vehicle toward the destination point and
    the path needed to avoid any obstacles on the way

Technical Approach
Circuit Schematic
Microcontroller Algorithm
  • Acceleration
  • Reacts Linearly to the Joystick Input
  • Joystick increases acceleration when pushed
  • Speed range is 0 to 15mph
  • Braking
  • Joystick increases braking when pulled backward
  • Can stop vehicle slowly or almost instantaneously

Microcontroller Algorithm - Turning
  • Turning
  • Joystick is used as input, steering encoder used
    as feedback
  • Both cover range from 0 to 5V, left to right
  • Voltages are compared for turning
  • If encoder has smaller voltage, wheels are
    signaled to turn right
  • If encoder has larger voltage, wheels are
    signaled to turn left

Microcontroller Algorithm - Communication
  • Serial Communication
  • If data is detected on the serial port and the
    joystick is in the neutral position, the vehicle
    will run autonomously
  • Serial data is ignored if the joystick is outside
    of the neutral position
  • ASCII value determine the actions of the GEM
  • Serial data need to be sent in pairs
  • Serial timeout present to prevent microcontroller
    from freezing while waiting for message

Autonomous Algorithm
  • System designed to home in on final point
  • Vehicle will go a constant speed unless no paths
    are detected or it has reached the final
  • Algorithm
  • If ( vehicle is close to the desired location)
  • Tell the vehicle that it has reached the final
    destination and stop the vehicle

Autonomous Algorithm - Continued
  • If ( Destination is almost directly North or
    South of vehicle)
  • Assign a predefined desired angle
  • Else
  • Convert the GPS coordinate system into a regular
    XY coordinate system
  • Then the desired angle is calculated using

Autonomous Algorithm - Continued
  • Desired angle is converted into the regular
    coordinate system
  • Heading angle is converted into the regular
    coordinate system
  • The difference in the desired angle and the
    heading angle is determined
  • From this difference, the bias path is returned
    to the obstacle avoidance algorithm
  • There are 5 predetermined paths the vehicle can
  • The bias path is the path toward the destination
    without accounting for obstacles

Obstacle Avoidance Algorithm
Testing Plan
  • Demonstrate manual GEM control via joystick
  • Tweak microcontroller code for functionality and
    ride smoothness
  • Ensure complete safety of system through testing
    of responsiveness as well as emergency cut-off
    and stopping procedures.

Testing Plan - Continued
  • Demonstrate the GEM moving from one location to
    another at the CE-CERT parking lot while
    detecting and avoiding objects
  • Create obstacle map while under manual control
  • Find current GPS location and path to desired
    location while under manual control
  • Allow vehicle to navigate autonomously to desired
    location via GPS without obstacles.

Testing Plan - Continued
  • Integrate obstacle map with path planning
    algorithm and find paths around obstacles to
    desired location while under manual control.
  • Full autonomous movement to desired location with
    obstacle detection and avoidance
  • Input multiple destination points into program.
    Vehicle should drive to each point, stop
    momentarily and continue to the next point

  • Mechanical Implementation Successful
  • Braking, Throttle and Steering respond correctly
    to joystick inputs
  • Steering Motor Mount does not flex while in use.
    Chain and sprocket are very durable and have no
    slack to add to the steering delay
  • Emergency Brakes have been tweaked to stop the
    vehicle as fast as possible

Results - Continued
  • PC Communication with sensors and microcontroller
    work well
  • Laser range finder updates the obstacle map at 1
  • GPS and Compass values are updated whenever the
    laser range finder updates
  • Vehicle runs autonomously with little difficulty
  • Vehicle detects obstacles and can maneuver around
    them to follow a clear path
  • Vehicle stops upon nearing the destination

Results - Continued
  • Minor Issues
  • Brake controller has a threshold voltage before
    it activates the brakes.
  • The joystick needs to be pulled back about a
    third of the way
  • Causes the braking to be very sudden
  • The steering is slow
  • Takes about 2-3 seconds to get from one side to
    the other
  • Laser Range Finder can only detect objects higher
    than 3 feet tall
  • Can be blinded by bright sunlight at the right

Future Work
  • Improvements to Design
  • Implement Reverse and other car controls into
  • Add ability for microcontroller to control
  • Allows vehicle to back out of traps
  • Buttons on Joystick can be mapped to horn,
    changing vehicle direction, or signaling
  • Add more safety features
  • Throttle cutoff if power to DAC circuit is lost
  • Component Cutoff switches near driver
  • Toggle brake lights when car is stopping

Future Work - Continued
  • Parking
  • Identify special obstacle and park in front of it
  • Update Faster
  • Stabilize the code for updating the obstacle map
    at 5Hz
  • Creation of PCB for DAC circuit
  • PCB has already been designed
  • Need to fix pin assignments
  • Improved Path Planning and Obstacle
    Identification Algorithms

Future Work - Continued
  • Application for Future
  • Identify an obstacle and follow it
  • Expansion to larger vehicle and system to compete
    in DARPA Grand Challenge
  • Next Slide Video
  • Focus on the two stationary GEM vehicles
  • Notice how it avoids the first one by turning
    right and then avoids the second one by turning
  • After the vehicle passes the obstacles, it
    realigns with the destination point and heads
    towards it
  • Vehicle stops very close to the desired
    destination point marked by the cone

  • (From Left to Right) Martin Lizarde, Thomas Fong,
    Adrian Afan, Zaynal Pham
  • Special Thanks to Dr. Barth, Dr. Beni and all the
    people who helped us with this project!
    G-g-G-gem unit

Appendix A - Budget
Appendix B - Cost Analysis/Alternate Solutions
  • Electro-Hydraulic Brake Controller
  • While it stops the vehicle very well, it is not
    smooth as originally assumed to be
  • Possibly because a dedicated brake controller
    with an internal accelerometer was not purchased
    with the system
  • Could be replaced by a linear motor operating the
    master cylinder
  • This would be smoother, but would need feedback
    to get proper braking

Appendix B - Cost Analysis/Alternate Solutions
  • SICK Laser Scanner
  • Provides a very accurate map of surroundings that
    it can see
  • Does not see small objects that fall underneath
    its field of vision
  • Needs to be supplemented by ultrasonic sensors
  • Cannot be replaced by ultrasonic sensors because
    they lack the range given by the laser scanner
  • Can be replaced by computer vision
  • Faster computer would be needed with good
    obstacle detection algorithms

Appendix B - Cost Analysis / Alternate Solutions
- Continued
  • Steering Motor
  • Faster Motor with Similar Torque
  • This would increase responsiveness of steering
  • Small amount of space available around mounting
  • Could be replaced with Linear Motor
  • Would need to be very strong to move tires
  • Novel mechanical mechanism could multiply force
    exerted on tires and ensure that the physical
    limits of steering mechanism are not violated