Feedback compensator for control units with proof-mass electrodynamic actuators

This paper presents theoretical and experimental work on a velocity feedback control unit with an electrodynamic proof-mass actuator. The study shows that the stability and performance of the feedback control loop can be substantially improved by implementing an appropriate compensation filter, which detunes the passive and active responses of the actuator. The control unit is analysed in terms of the open- and closed-loop base impedance it presents to the structure under control. In this way the analytical expression for the proposed compensator is derived directly from known actuator parameters. The compensation filter provides significant improvement over the uncompensated case, even for considerable variations in the actuator response. One drawback of the compensator is the enhancement of the feedback signal at low frequencies, which may lead to stroke/force saturation effects in the actuator. In this respect the study shows that it can be beneficial to implement an additional high pass filter, which however produces a loss in the phase and gain margins.