Filter-based control for parallel plate micro electrostatic actuators

In this paper, a filter-based nonlinear control strategy for parallel-plate micro electrostatic actuators is designed. The proposed control technique utilizes the measurements of the micro actuator's movable plate displacement and the device internal charge. The information of the micro actuator's movable plate velocity is utilized as well in the control synthesis but since it is difficult to be measured, filtered signals are designed and utilized to facilitate the control development. A Lyapunov-based analysis is presented which proves that a desired time-varying displacement of the micro actuator's movable plate is accurately tracked. The proposed nonlinear controller is capable of controlling the movable plate beyond the pull-in boundary that is one third of the capacitive gap. Representative numerical simulations are introduced to demonstrate the performance of the proposed filter-based nonlinear control strategy in accurately tracking the deflection of the micro electrostatic movable plate within the entire capacitive gap. Finally, a comparison with a standard PID controller is also presented to demonstrate the effectiveness of the proposed control design.