Closed Loop Sense Feedback Control for a Dual Proof Mass MEMS Vibratory Gyroscope

A standard inertial navigation system utilizes gyroscopes to measure the angular velocity. MEMS gyroscopes designed for inertial-grade applications must exhibit excellent bias stability and achieve remarkable resolution. Most MEMS gyroscopes rely on capacitive measurements of angular rates due to the Coriolis force acting on a moving suspended mass along a specified sense direction. A dual-proof mass gyroscope has significant advantages over a single-mass gyroscope as it offers fewer errors because of the introduced coupling effect between two masses. In the proposed model, diamond coupling between the proof masses enhances the resonant frequency. The response by open loop structure is compromised due to nonlinearity in the relation between capacitance change and sense comb displacement, and nonlinear behavior of the signal-conditioning circuit. However, a closed loop takes the open loop response as an input and helps to achieve the sensor response in the linear range. This paper presents the utilization of automatic gain control (AGC) and phase-locked loop (PLL) techniques in a dual mass MEMS gyroscope (DMG) to enhance its performance and stability. The applied demodulation technique in the DMG for accurate angular rate sensing effectively extracts angular rate information from the sensed signals, enhancing precision and reliability in motion tracking and inertial measurement applications. Finally, our developed model in
$\text{MEMS}^+$
can deliver in-phase-controlled voltage to the sense feedback to control the motion of proof mass in the sense direction and gives the desirable demodulated output for the given input angular velocity.