Electrical Control of Effective Mass, Damping, and Stiffness of MEMS Devices

We propose the use of electrostatic force feedback to control the effective mass, damping, or stiffness of micro electro mechanical system (MEMS). Our analysis suggests that if feedback force is proportional to sensed displacement, velocity, or acceleration of a MEMS proof mass, then feedback can be used to increase or decrease the apparent stiffness, damping, or mass of the system. Such feedback might be used to compensate the process variations, packaging stress, thermal drift, and damping. Prior efforts by others include position or velocity-based feedback for modifying frequency, bandwidth, quality factor, or sensitivity of resonators. However, we present a comprehensive means of controlling the response of MEMS. We develop an analytical steady-state MEMS model that includes feedback forces and circuit delay, and we develop a stability model. Our analytical models are verified using numerical simulations that include circuit delay, electrical feedback delay, and noise. Our results support the realization toward performance-on-demand MEMS (PODMEMS).