Midband resonance compensation

[sp1nm0nkey]

I've heard a lot about the theory of what midband resonance is in stepper motors (the restoring force of the cogging forms an oscillator, and when the stepper motor is driven at the resonant frequency of the oscillator, the amplitude exceeds the step distance and it goes nuts), but I haven't found any information on how the compensator circuit works. I'd really appreciate it if someone would enlighten me.

[amplexus]

The midband resonance circuit adds a derivative component (+80 degrees
phase lead) to the system phase angle to eliminate parametric
resonance. It involves sensing the rate of motor load change
(derivative of motor torque) which then phase modulates the internal
step pulse timing.

This is all Mariss has to say ans I hesitate to add to it except to say running closed loop also fixes the problem.

Amplexus Ender