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Optimal Line following configuration — Parallax Forums

Optimal Line following configuration

LoopyBytelooseLoopyByteloose Posts: 12,537
edited 2012-05-19 10:05 in Robotics
Hello,
I've been trying to figure how many sensors and in what geometry seem to be best for line following. For some reason I think a cross with one in front of the drive wheel axles, a left and right on the axle, and one following might be the best.

But I am by no means sure about this. There may be different situations where different set ups have superior performance.

Comments

  • kwinnkwinn Posts: 8,697
    edited 2010-11-19 15:09
    I am not so sure I agree. Think of when you are driving a car. The further you can see down the road the better you can anticipate and negotiate the curves. If you are prevented by weather or traffic from seeing so far ahead you tend to wander and over correct more.
    A line following robot's software may not be able to anticipate the curves but there may be an advantage to having the sensors as close to the front as possible. At the very least an early warning may allow the robot to slow down and start the turn earlier.

    PS - What purpose would the fourth trailing sensor have? I don't see any use for it.
  • ercoerco Posts: 20,256
    edited 2010-11-19 22:15
    Check out http://www.pololu.com/catalog/product/975 for a fast, optimized line follower. Copy that.

    http://www.youtube.com/watch?v=mJV-KDqHgDQ
  • agfaagfa Posts: 295
    edited 2010-11-20 04:25
    I found that an array of five sensors in a line, in front of, and parallel to the axle worked best for me. The further ahead of the axle the better. I spaced the sensors close enough together that at least one sensor could see that line at all times. This sensor arrangement was for solving a maze that consisted of straight lines 90 degree turns, Tees, and crossed lines.

    agfa
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2010-11-20 06:17
    Thanks.

    It seems that 5 sensors is what you agree on as a count. But the geometries differ a bit.

    The Polou seems to have 5 in a circular arc that is equidistant from the center of the drive axle.

    The other option suggests a parallel line to the drive axle. Personally, the Polou design seems more attractive to me, but certainly more demanding to build from scratch.
  • ercoerco Posts: 20,256
    edited 2010-11-20 21:26
    Timing is everything!

    http://forums.parallax.com/showthread.php?t=127316
  • FranciscoTavaresFranciscoTavares Posts: 27
    edited 2012-05-18 19:57
    The best geometry for a line follower is a circle formed by sensors.
    With this kind of geometry the robot has information about distance as well as the angle of the path.
    The interface for this sensors set should be a serial one because it requires a lot of io pins and the processing software is much more complex as well.
  • ercoerco Posts: 20,256
    edited 2012-05-19 10:05
    "Best" configuration depends on many specific factors. Vehicle dynamics, sensor location, line type (curved or 90-degree turns) are a few. I can make a case for having two different sensor arrays, one looking just ahead of the vehicle centerline and one looking farther ahead to anticipate turns and decelerate.
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