High precision massive shape control of magnetically levitated adaptive mirrors

The paper presents a control scheme that provides precise active shape control of deformable mirror shells using a very large number of control points. The proposed controller combines a low frequency centralized feedforward and a high frequency fully decentralized feedback, with each single actuator mated to a single sensor. To grant a precisely controlled shape the feedforward part requires an accurate knowledge of the system stiffness. For this purpose a viable experimental identification procedure for high dimension steady state response matrices is described and verified through realistic simulations. Finally the control methodology is applied to the model of an adaptive secondary mirror with 3360 control points. Numerical results confirm the validity of the proposed approach.