Duplex mode tilt measurements based on a MEMS biaxial resonant accelerometer

This paper firstly reports the duplex mode tilt measurements (biaxial tilt measurement with small angle range and uniaxial tilt measurement with large angle range) based on a micro electromechanical system (MEMS) biaxial resonant accelerometer. For the accelerometer, two pairs of double-ended tuning fork (DETF) resonators are the sensing elements and they are integrated with a single proof mass. The two-stage microleverage mechanisms, possessing higher amplification factor, amplify and translate the weight component to the resonators. The adoption of decoupling beams lower the cross impact and allow the simultaneous differential measurement of tilt angles acting along two orthogonal axes. Based on the biaxial sensing structure, the biaxial tilt measurement is realized on the two orthogonal sensing axes. By the combination of the four DETFs resonant frequencies at each angular position, the linear range of uniaxial tilt measurement is extended. For the biaxial tilt measurement with small angle range, the experiments demonstrate a high sensitivity (X-axis: 4.351 Hz/deg and Y-axis: 5.257 Hz/deg) and a low cross-axis sensitivity (X-axis: 0.180 Hz/deg and Y-axis: 0.202 Hz/deg) for a +/- 40 degrees biaxial tilt angle range. For the uniaxial tilt measurement with large angle range, the device shows an average sensitivity of 3.973 Hz/deg for a +/- 90 degrees range. In addition, the close-loop self-oscillation is realized and the minimum Allan deviation of 68 ppb is obtained. The performance makes the device a potentially attractive option for compact, multi-functional and highly-sensitive tilt measurements. (C) 2019 Published by Elsevier B.V.