Modeling and Calibration of a Capacitive Threshold Sensor for In Situ Calibration of MEMS Gyroscope

A capacitive sensor design is introduced with an associated method for constructing a trusted threshold crossing angle (theta(TH)) from the capacitance profile to perform precise measurement of the out-of-plane (X and Y) tilting angles of a 6 degree of freedom (DOF) piezoelectric actuation stage for in situ calibration of micro electromechanical (MEMS) gyroscopes. The capacitance vs. tilting angle relationship of the sensor is calibrated with the assist of an external Laser Doppler vibrometer (LDV) and a closed-form model of the sensor. The theta(TH) are extracted by detecting the crossing location of the reconstructed capacitance trajectories using measurement from LDV or on-chip capacitive sensor, the comparison shows close agreements. The experimental results demonstrate: (a) the on-chip capacitive sensor is able to track the tilting motion with high accuracy; (b) the theta(TH) extracted from on-chip capacitive sensor can serve as an invariant reference point for scale factor calibration of MEMS gyroscopes.