Modeling aspects and gain scheduled H∞controller design for an electrostatic micro-actuator with squeezed gas film damping effects

In this article the modeling and control design aspects of an electrostatic microactuator (EmA) with squeezed thin film damping effects are presented. The modeling analysis of the squeezed film damping effect is investigated in the case of an EmA composed by a set of two plates. The bottom plate is clamped to the ground, while the moving plate is driven by an electrically induced force which is opposed by the force exerted by a spring element. The nonlinear model of the EmA is linearized at various operating points, and the feedforward compensator provides the nominal voltage. Subsequently a gain scheduled H_infin controller is used to tune the controller-parameters depending on the EmA´s operating conditions. The controller is designed at various operating points based on the distance between its plates. The parameters of the controller are tuned in an optimal manner and computed via the use of the Linear Matrix Inequalities. Special attention is paid in order to examine the stability issue in the intervals between the operating points. Simulation results investigate the efficacy of the suggested modeling and control techniques.