I tried out the virtual pendulum idea today. The idea is to compensate the physical pendulum via the control system, and then add a virtual pendulum formed in the control system. We know the actuator TF from p. 5900 and apply its inverse to the C1:SUS-MC?_SUSPOS filters. Also we add an pendulum Q=3 with a resonance frequency of 0.1Hz to the POS control loops.
The result is pretty awesome!
1. Black: Standard config. Wfs on. New Cheby filter in place ( p. 6031 )
2. Red: With virtual pendulum. Extra eliptic LP filter @ 2.5Hz
This is stable for 5-10minutes, at which point it falls out of lock, swinging in yaw.