Oscillation Loop for a Resonant Type MEMS Accelerometer and Its Performance

Abstract

This paper presents an oscillation loop for an INS (Inertial Navigation System) grade, surface micro- machined differential resonant accelerometer. This resonant type sensor utilizes the electrostatic stiffness changing effect of an electrostatic actuator. This device produces a differential digital output upon an applied acceleration. A closed loop system called self-sustained oscillation loop is prerequisite for its operation as a resonant accelerometer. 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 nonlinear dynamic system. The oscillation loop is regarded as a limit cycle. From the standpoint of feedback control system, both determination of resonance point and its stability analysis are required. In the actual system, which has several noise sources, noise can affect the output resonant frequency. We analyzed the effect of a noise on oscillation frequency bias stability and a resolution of the sensor. Finally, the simulation and experimental results for a resonant type accelerometer is given.