An enhanced dynamic model for the actuator/amplifier pair in AMB systems

Typical models for AMB actuators consist of a static linearized mapping from displacement and current to force (f ˜-Kxx+Kii) and are augmented with actuator dynamics (bandwidth and gain) which act to correlate a command signalVc to resulting current: I(s)=Ga(s)Vc(s). In the present work, we show that this model misses a number of potentially important features, most notably the effect of amplifier bandwidth limitations on the term mapping displacement to force (Kx) and the related influence of journal motion induced back-EMF. In addition, we show how actuator eddy currents interact with the amplifier dynamics and how to model the resulting composite system.