Active structural error suppression in MEMS vibratory rate integrating gyroscopes

Due to restrictive tolerancing in microfabrication, structural imperfections that reduce performance of fabricated micro devices are typical. In microelectromechanical vibratory gyroscopes, feedback control is a common strategy in attempting to correct the imperfections. However, a purely feedback control can be insufficient for compensation of all the errors, requiring post processing in the form of laser trimming to achieve higher levels of performance. In this paper, we explore another alternative: the design and implementation of a dual stage control architecture with self-calibration and feedback capabilities. The self-calibrative portion of the control identifies and electronically "trims" large imperfections, while the feedback control compensates for remaining small nonidealities and in-operation perturbations. Presented here is an algorithm for in-situ imperfection identification based on the dynamic response of the device. A realization of the dual stage control architecture is proposed for a gyroscope using nonlinear electrostatic parallel plate actuators. Modeling and simulation results which demonstrate successful compensation of imperfections with the proposed architecture for a device with 10% fabrication error appearing in the form of stiffness nonidealities and subjected to further 1% in-run perturbations are presented.