Modal actuation for high bandwidth nano-positioning

In high speed AFMs the vertical axis of the sample positioning stage requires high bandwidth feedback control. In these systems the dynamics of the piezoelectric actuator, its support structure and load play a dominant role in the design of the feedback loop. System performance can be increased by avoiding the excitation of resonant modes of the piezoelectric actuator by modal actuation. In this approach, the piezoelectric actuator is modified to render modes close to the controller bandwidth uncontrollable. Due to its static hardware implementation robustness issues may emerge due to varying loads used for AFM imaging. This paper focusses on performance robustness of modal filters due to load variation.