Making consistent 90 degree turns

I have made a tractor robot out of my activitybot 360 by adding another platform to hold more servos and arms for sprayers. When I program it to run my field 1 run will be perfect with 90 degree turns but then the next time I try the turn will be off. What can I do. Could it be the extra weight I've added causing the problem?tractor.pdf


  • I think you need to add a compass as there is slippage in the wheels as they turn and small variations in the encoder make it difficult to correct for.

    If you are interested, here is the real thing:


  • ercoerco Posts: 19,587
    How big is this tractor robot? Are there treads? Got a photo?
  • The picture of the tractor is in the PDF.

    I built something like that, except I 3D printed it and tried to do a LOGO language with it only to find out it doesn't always turn the way you want it to.

    At least a compass will tell you what direction your pointing too.


  • ercoerco Posts: 19,587
    If you are actually running on dirt, that introduces lots of slippage and variables. Dead reckoning via precise wheel rotations will not yield consistent navigation results. A compass may help, depending on the resolution and accuracy you require. Otherwise, GPS, lasers, or line following. Some AGVs can follow a wire buried in concrete, but that might not work in soil.
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