Robust design of a decoupled vibratory microgyroscope considering over-etching as a fabrication tolerance factor

Abstract

A robust optimal design of a bulk-micromachined, decoupled vibratory microgyroscope was carried out to determine geometric dimensions such that the gyroscopic performance is least affected by a fabrication tolerance. Electro-mechanical vibration analysis considering the sensing electrodes and the electronic signal processing were performed to obtain the frequency responses that influence the gyroscopic performance. A statistically distributed lateral over-etching (LOE) developed in the fabrication process was selected as a fabrication tolerance factor. The dimensions of the driving and sensing spring are selected as design variables which are the sum of deterministic mask dimensions and the LOE. To minimize the influence of LOE on the decoupled vibratory microgyroscope performance, the multi-objective function was formulated so as to minimize the sensitivities of the frequency difference with respect to the LOE. As a result, the standard deviation of the frequency difference and the driving natural frequency are reduced to 78% and 8%, respectively, through the Monte Carlos Simulation (MCS).