No abstract

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. Finiteelement 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. [261]

In this paper, we develop a new approach in order to understand the origin of the quadrature error in MEMS gyroscopes. As the width of the flexure springs is a critical parameter in the MEMS design, it is necessary to investigate the impact of the width variations on the stiffness coupling, which can generate a quadrature signal. To do so, we developed a method to determine the evolution of the stiffness matrix of the gyroscope springs with respect to the variation of the bending beams width of the springs through finite element analysis (FEA). Then, a statistical analysis permits the computation of the first two statistical moments of the quadrature error for a given beam width defect. It turns out that even small silicon etching defects can generate high quadrature level with up to a root mean square (RMS) value of 1220°/s for a bending beam width defect of 0.9%. Moreover, the quadrature error obtained through simulations has the same order of magnitude as the ones measured on the gyroscopes. This result constitutes a great help for designing MEMS gyroscopes, as the consideration of the bending beams width defects is needed in order to avoid high quadrature error.

No abstract