[Levansic]

One thing that did frustrate us, was the ease of going into a protected stop condition. Not really sure what to call the state, but we hit it often when trying to optimize our bridge tipper, while using closed loop current control.

Stall currents generally follow Ohm's law, since the motor armatures are not moving, at least when in steady state. We had several trips of the jaguar, before hitting 20 Amps (24 A stall current at 12V), and never saw voltages approaching the battery voltage. At lower currents, performance was reliable, but not enough torque for what we needed.

Now, we dont have an oscilloscope, so the back current spikes due to rapid voltage increases may have been huge, but the jaguar would sometimes failsafe out before there was any discernable movement in the attached motor. If we decreased our PID gains, the jaguar would not source enough power to get the motor moving. Not sure this is clearing much up, but we found the tuning to be finicky, and not robust when the temperature of the attached motor changed. If there was filtering on the feedback signal, or if a voltage output ramp rate could be enforced along with the PID, then this problem could be minimized or eliminated.

There was an earlier thread on PID speed control here. We thought we could tame that beast, but the fast sampling rate on the encoder, coupled with lots of backlash in our tough box nano gear boxes, made the feedback too noisy, and the control loop far to unstable to use. Not sure if there is any filtering on the feedback signal, in the jaguar PID code, but there should be.

We intend to do a lot of testing and characterization work this summer.

-- Len