Quote:
Originally Posted by Kevin Sevcik
PID traction control is pretty simple, just not anything that's typically done in FIRST. The whole point is to keep your wheels from slipping. Wheels slip when applied force exceeds the static friction force. Applied force is proportional to applied torque which is (mostly) proportional to motor torque which is proportional to motor current. So your goal would be to PID control the current being supplied to (or sourced from) the motors. Current-mode motor drivers and amplifiers are awesome for this, but we don't have any, sooo the idea would be to use a solid state current sensor on your motor leads, and PID control this.
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This thread has spawned a lot of good discussion. While we're on the topic of traction control, I wanted to ask another question, how exactly does an anti-lock brake system on a car work? This would seem to require some sort of a traction control system, where you would PID control the current of a motor (or for a car, the gas being injected into the engine). Theoretically, this control system would work when the wheel material and the ground were made of the same material, as is the case in a FIRST competition.
But for cars, the problem is much more challenging, because road conditions are always different. ABS systems allow fairly large deceleration on dry roads, but when the road is wet or icy, this is somehow compensated for and maximum deceleration is much smaller. Can anyone explain this? This concept seems like it would be extremely useful if it could be applied to a FIRST robot.