(...) In 'The LEGO Lugger', previously posted at (URL) the extended drive shafts for both sides of a tracked vehicle, moving in opposite directions, are summed in a differential with the difference (hopefully zero)fed to the rotation sensor. Because (...) (23 years ago, 13-Jan-02, to lugnet.robotics)
(...) I believe that in this case, you should use a light sensor looking at a wheel that's white with a black line marked on it. The software for reading this is identical to what you would use for line following (a very well researched topic!) - (...) (23 years ago, 14-Jan-02, to lugnet.robotics)