Nonlinear dynamic output feedback stabilization of electrostatically actuated MEMS

Operating regions of electrostatically-actuated microelectromechanical systems are limited by a bifurcation phenomenon called "snap-through" or "pull-in". It is known that charge feedback control can be employed to avoid this bifurcation. The performance of such controllers may be poor, especially if the natural damping of the system is very low or very high. This paper discusses two possible feedback control strategies that eliminate snap-through as well as improve performance. A serious drawback of these control laws is that they require the measurement of the device velocity. A reduced order observer is presented to overcome this. The observer is based on well known nonlinear observer design techniques, and can be assigned arbitrary linear error dynamics.