Control of an Electrostatic Microelectromechanical System Using Static and Dynamic Output Feedback

Abstract

This paper examines control strategies for electrostatically actuated microelectromechanical systems (MEMS), with the goals of using feasible measurements to eliminate the pull-in bifurcation, robustly stabilize any desired operating point in the capacitive gap, decrease settling time, and reduce overshoot. We show that input-output linearization, passivity-based design, and the theory of port-controlled Hamiltonian systems lead naturally to static output feedback of device charge. This formalizes and extends previously reported results from the MEMS literature. Further analysis suggests that significantly improving transient behavior in lightly damped MEMS requires dynamic estimation of electrode velocity. We implement output-feedback control using a reduced-order nonlinear observer. Simulations predict greatly improved transient behavior, and large reductions in control voltage.