Precise Oscillation Loop for a Resonant Type MEMS Inertial Sensors

Abstract

This paper presents an oscillation loop for an INS (Inertial Navigation System) grade, surface micro-machined differential resonant accelerometer and in-plane vibratory gyroscope. This resonant type sensor utilizes the electrostatic stiffness changing effect of an electrostatic actuator. A closed loop system called self-sustained oscillation loop is prerequisite for its operation as a resonant accelerometer. And precision driving mode oscillation is important to the vibratory gyroscope. A self-sustained oscillation loop induces the system's dynamic states into its primary mode, thus keeps track of its resonant state under applied acceleration or perturbation. For this, a simple self-sustained oscillation loop is designed and the feature of the loop is analyzed in the viewpoint of a nonlinear dynamic system. For the efficient and stable self-sustained oscillation loop, we obtained the proper slope of the nonlinear and phase shifting coefficient from the analytical results. Finally, the simulation and experimental results for a resonant type accelerometer and vibratory gyroscope are given.