Fisher Price Motor Power

[vamfun]

Originally Posted by Joe Johnson

If you can use a Jaguar and use CAN, you can easily know the current. There are other ways to measure or infer current (sensors, shut resistors, measure speed & calculate, etc.). Once you have current you can easily build a "how close to tripping the FP bi-metal breaker am I?" model. It will not be too hard. If you are using Labview, I think it may be trivial.

As a controls engineer, this was my first thought but from this thread it seems the problem requires motor speed to be of any use. When Al and I were pondering the Jaguar linearity vs frequency phenomenon, I had proposed a BackEMF motor speed project but never got around to doing it last summer. I wish I had so we could just use the CAN bus and motor voltage to create a current trip schedule without the use of an encoder.

The trip level could be as simple as a linear function of speed. So when running at speed "w" we set the trip at w/w_free*i_Stall+ delta where the delta is the safety current margin. When stalled , the motor would shut down if current was > delta. Of course there would probably be time elements involved. delta would probably be on the order of a few amps to 10 amps depending on the "allowed time to exceed the scheduled limit" criteria.


Apologies to AL for not picking up on the bi-metal distinction.