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GPSBased Location Determination

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Start turning when distance from vehicle to vertex is less than or equal to Length ... Wheeled robots used as outdoor tour guides or security guards. ... – PowerPoint PPT presentation

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Title: GPSBased Location Determination


1
GPS-Based Location Determination
J. Walker / A. Zhang / B. Azimi-Sadjadi / P.S.
Krishnaprasad
Control Algorithm
Simulated Results
Introduction
  • 24 GPS satellites spaced around Earth in 6
    orbital planes transmit an amplitude-modulated
    clock signal and navigation message that includes
    the time the message was sent and other error
    information
  • GPS receiver determines the time taken for the
    signal to travel from satellite to receiver and
    calculates a pseudorange by multiplying by the
    speed of light.
  • GPS receiver calculates position relative to
    Earth knowing at least four pseudoranges with
    satellite positions and error information
  • Differential GPS determines accurate position by
    broadcasting range errors from a base receiver
    with fixed known location to one or more rover
    receivers
  • ISL has previously developed a radio-controlled
    vehicle built on a commercial platform that can
    navigate using differential DGPS
  • Simulated vehicle was successful in traversing
    predefined paths such as straight lines, grid
    paths, star paths, irregular paths, and
    elliptical paths.
  • Use flag e to tell whether in turning state or
    in straight-line state
  • Calculate initial turning point (p1x, p1y) of
    circle inscribed within corner
  • Determine Length, distance from turning point to
    vertex corner
  • Start turning when distance from vehicle to
    vertex is less than or equal to Length
  • Determine chord length D of inscribed circle
  • Stop turning once distance from vehicle to
    initial turning point is greater than or equal to
    D
  • Reset flags e and d to regain a straight line
    state

Increasing Path Complexity
Experimental Results
DGPS Setup
  • Vehicle was able to steer in real-time with
    simulated paths described above
  • Steering was controlled by the software while
    throttle was controlled by pulling the vehicle
    using two strings tightened at front. This
    method made it easy to maintain and reduce the
    speed of the vehicle, thus reaching better
    accuracy than a gas powered vehicle.
  • Real-time DGPS controlled experiment could not
    be performed due to a malfunctioning GPS receiver


Turning Stage Diagram
Differential GPS Setup
  • Base and Rover antennas connect to commercial
    DGPS receivers
  • Receivers communicate correction data using
    radio modems
  • Base receiver sends positioning information to
    laptop through Comm port
  • Laptop makes control decisions, sends digital
    control signal to D/A card
  • D/A card sends analog signal to input of remote
    control
  • Remote control sends radio wave signal to
    vehicle
  • Vehicle receives radio wave signal for control
    of servos associated with steering and
    throttling, navigates to a new position

Interior steering unit
Meter-long RC Car
Applications
Inscribed Turning Circle
GPS Application
  • Self-navigation of
  • Farming machines which follow irregular-shaped
    paths for long distances.
  • Wheeled robots used as ticketing authority in a
    parking lot.
  • Wheeled robots used as outdoor tour guides or
    security guards.

Control View
What We Did
  • Create new child frame class, create sizeable
    grid with axes
  • Associate left and right mouse clicks with
    functions to record points on grid
  • On left click, store points in local array
  • On right click, map points from Control View
    grid to Global Map grid
  • Test differential GPS system from previous year
  • Modify control algorithm so that vehicle may
    turn and follow predefined paths that include
    both angled corners and straight lines
  • Create a Control View window to help simplify
    path input
  • Test software with various paths in simulation
    and real-time mode

Control View Window
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