Preliminary results on a silicon gyrometer based on acoustic mode coupling in small cavities

A silicon vibratory gas angular rate sensor has been developed by means of micromachining techniques. It is a shockproof sensor because it has no movable part. This device is a miniaturized form of an instrument, which has been previously fabricated in a conventional technology format and called the acoustic gyrometer. The working principle of this sensor is based on acoustic coupling between two orthogonal modes of a closed cavity, due to Coriolis forces effect on vibrating gas particles. The gyrometer, which is presented in this paper, was fabricated by a silicon process. It is constituted by an acoustic cavity and four microphones: one to generate an acoustic wave, one to slave the cavity at its first resonance frequency, and two for the measurement of the angular rate effect. Finite element modeling (FEM) modal analyses were performed on two cavity shapes: cylindrical and trapezoidal, corresponding to the fabricated devices. The results are compared with available analytic solutions and with measurements.