A Monolithic Triaxial Micromachined Silicon Capacitive Gyroscope

This paper presents the design, simulation, fabrication and preliminary test results of a monolithic triaxial micromachined vibratory gyroscope. The device is a monolithic integration of two uniaxial in-plane (x- and y-axis) gyroscopes and one uniaxial out-of-plane (z-axis) gyroscope and the three individual gyroscopes are all actuated by electrostatic force and detected by capacitors. In order to study the vibrating characteristic of the device thoroughly, the designed structures of the gyroscope were analyzed in detail theoretically and simulated using FEM (Finite Element Method) program ANSYS8.1. The triaxial gyroscope was fabricated on a common glass substrate by bulk silicon dissolved wafer process, which could realize large proof-mass and sensing capacitance, therefore improving the sensitivity of the gyroscope. The driving characteristics of the three uniaxial gyroscopes at atmospheric pressure were tested and the results indicated that the maximum error between the practical resonant frequencies and the theoretical ones was within 5% meeting the design requirements. The triaxial gyroscope is estimated to have a scale factor of 14.5mV/(deg/s) over the range of plusmn300 deg/s