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Unread 15-02-2009, 00:22
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Re: 2809 - Traction Control Demo

Quote:
Originally Posted by Mr.G View Post
We are using a torque sensor on each wheel. You can only apply so much torque to a wheel before it slips. Since everything is constant (robot weight, playing surface, wheel, ...) then all you have to do is apply power to the wheel till you reach a predetermined torque target and the wheel will not slip and you will approach max acceleration and pushing power.

I don't know if this is how you are doing it, I am guessing, but that is what we are doing.
A torque sensor? I never thought of that. May I see which particular sensor you are using?

Anyway, it turns out the torque a DC motor produces is related only to the voltage (effective) you are sending it and the rpm of the motor. We measure the rpm of the motor with the encoder, plug that into the equation, and get back the maximum voltage we can send without causing enough torque to slip.

The beauty of the system is that it involves no PID loops, no tuning, no trial-and-error. We have about 15 measureable constants and 2 measureable variables (battery voltage and motor rpm), but nothing needs to be manually tuned. Yay for physics.