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localisation

Discussion in 'Electronic Basics' started by New², Sep 4, 2004.

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  1. New²

    New² Guest

    Hello,
    I have three small Automated Guided Vehicle wich navigate in a 700*700
    square feet area. Using à PC, i want to know at each moment where every one
    of these robots is. What are the different method i can use wich give
    precise results.
    Thanks
     
  2. Rich Grise

    Rich Grise Guest

    Keep track of its motion, obviously, but maybe three transponders and
    a little triangulation?

    Good Luck!
    Rich
     
  3. CFoley1064

    CFoley1064 Guest

    Subject: localisation
    I would guess radio beacons would give you all kinds of problems in near field.
    If it's an open area with clear sight lines, you might want to try three LED
    beacons in the corners (modulating at discrete and easily filterable
    frequencies), and put a rotating sensor with a lens in front of it on each
    vehicle, along with the intelligence to do its own triangulation of the
    identifiable light sources or at least report angular position of the three
    beacons. The vehicles could then transmit each in turn to your PC, by radio
    link if you prefer.

    Half-stepping a good stepper motor for the sensor should get you within better
    than a degree for the angle on each of the three beacons, which will give you
    an accuracy of within a couple of feet in the x and y axis from any position.
    Also, by measuring signal stength at adjacent steps, you might be able to
    improve the accuracy just a bit.

    This is the type of problem that is very amenable to large infusions of cash to
    achieve better results. But if you've got some experience in electronics as
    well as robotics, it is doable.

    Good luck
    Chris
     
  4. In that size area a RFID tag on each plus three transevers might work .
    It depends on if the area is empty or full of walls also.

    Charles.
     
  5. Maybe GPS will work:

    http://www.cs.kent.ac.uk/projects/mobicomp/Fieldwork/Notes/gps_if.html

    You might use a wireless 802.11 link between the handheld and your
    desktop. It won't give you totally precise values, but it should be
    relatively accurate to a meter or so. If you get a 4th GPS unit, you
    might be able to use differential GPS to locate the roving systems
    exactly.

    Regards,
    Bob Monsen
     
  6. New²

    New² Guest

    In that size area a RFID tag on each plus three transevers might work .
    Yes, the area contain many walls.
     
  7. Gordon Youd

    Gordon Youd Guest

    I'd like to throw my three pennyworth into the pot.

    Would it be possible to lay a matrix of wires on the floor area and give
    each robot a unique coded frequency fed to a coil in the base.

    The X and Y wires could be interrogated for a pulse and the frequency would
    denote which robot was over a junction.

    It's just an idea, someone may be able to enlarge on.

    Kind regards, Gordon.
     
  8. With walls light based systems aren't really usable. So use some form of RF.
    RIFD tags are smallish and already exist. Using a tranmitter on each unit
    requires only that they have different frequencies and that the signal
    proccessing used be differential . By comparing each receivers signal
    strength against the other two you can form a location even if the
    transmitter is weaker with time.More receivers will also give improved
    location.

    Charles
     
  9. andy

    andy Guest

    Tile the floor area in a checkered grid like this:

    - alternating black and white squares, but each black square has a
    thin white stripe down the centre, thinner than the floor area of the
    robot, and each white square has a black stripe. The stripes are all
    facing north-south.
    - Add in a series of barcoded north/south and east/west stripes every
    so-many grid squares, which give an absolute reference, in case of
    counting errors.
    - have an array of reflectivity sensors on the bottom of the robot, which
    looks at the floor and works out where it is in the grid pattern by
    counting transitions from one grid square to the next.

    you should be able to work out some algorithm based on this that will work
    out where the robot currently is.
     
  10. Dingo

    Dingo Guest

  11. James Newton

    James Newton Guest

  12. James Newton

    James Newton Guest

    <SNIP>

    And you can certainly do more than just half step, for example, the
    Linistepper controller supports up to 18th over stepping or 3600 steps
    per revolution from a standard 200 motor.

    http://www.piclist.com/techref/io/stepper/linistep/index.htm
     
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