Design and Analysis of a Tri-Axis Gyroscope Micromachined by Surface Fabrication

Abstract

This paper presents an innovative microgyroscope design. Solely by planar fabrication and wet etching, the proposed microgyroscope is capable to detect three-axis angular rates. The induced motion of individual seismic mass modules are designed to respond in the directions orthogonal to each other in order to decouple the obtained measures. In our work, three pairs of high-resolution differential capacitors with signal processing circuits are employed to measure the angular velocity components in three axes. On the other hand, the drive electrode comb is used to constantly vibrate the outer-ring in tangential direction by sinusoidal voltage. The signal bandwidth about the principle axis is increased by distributed translational proof masses, placed 90deg apart orderly around a circle. Each individual translational proof mass is designed to move in radial direction so that superior mode matching (i.e., resonance mode) can be easily, to some extent, achieved. The planar suspension flexures are particularly designed in geometry to resist acceleration in drive mode but increase the stroke of tilting angular displacement of the outer-ring such that the resolution of detected angular rate for the corresponding sense mode is upgraded. By considering the complicated geometry of the suspension flexures, finite-element method (FEM) is employed to examine the potential maximum induced mechanical stress. The dynamic equations of the proposed gyroscope are established are well so that the embedded gyroscopic effects are unveiled. More importantly, the efficacy of the drive and sense circuits modules is verified by commercial softwares Hspice and Multisim. By intensive computer simulations and preliminary experimental studies, the resolution, bandwidth and sensitivity of the tri-axis gyroscope are expected to be fairly enhanced if a certain degree of tradeoff is preset.