Modelling and control of an electrostatically actuated torsional micromirror

Abstract

This work aims at developing control algorithms for an electrostatically actuated torsional micromirror, extending the operational range of the device to a full 90° tilt angle. The analytical model of the micromirror equipped with an additional vertical electrode is established. Since the geometrical extent of the device is comparable to the air gap, the effect of the fringing field is also incorporated into the model. It is shown that the considered system is differentially flat and, based on this property, a closed-loop control scheme is constructed for both scanning control and set-point control. In addition, the desired performance can be specified through reference trajectories, allowing the control system tuning to be performed in a systematic way. The simulation results demonstrate the advantage of the developed control scheme over the constant voltage control.