Integrated charge and position sensing for feedback control of electrostatic MEMS

Closed-loop control of electrostatic MEMS requires sensing to provide a feedback signal. We present an integrated sensor for charge and position that negligibly affects the open-loop dynamics, does not increase the device footprint, and may be easily fabricated. Numerical finite-element simulation, incorporating a realistic electrostatic field model, and experimental results validate the functionality of the sensor. Simulations show how the sensor may be used in conjunction with nonlinear control to provide full gap operation and improved transient performance. Nonlinear control is often considered too complex for convenient implementation, however the controller presented may be implemented using on-chip, local, integrated circuit components.