Control-structure interaction in piezoelectric deformable mirrors for adaptive optics

This paper discusses the shape control of deformable mirrors for Adaptive Optics in the dynamic range. The phenomenon of control-structure interaction appears when the mirror becomes large, lowering the natural frequencies fi, and the control bandwidth fc increases to improve the performance, so that the condition fc < fi is no longer satis&#64257;ed. In this case, the control system tends to amplify the response of the &#64258;exible modes and the system may become unstable. The main parameters controlling the phenomenon are the frequency ratio fc / fi and the structural damping s. Robustness tests are developed which allow to evaluate a lower bound of the stability margin. Various passive and active strategies for damping augmentation are proposed and tested in simulation.