Novel design concept of torsional gyroscope with robust drive mode and its implementation

Abstract

This paper reports a novel design concept of torsional gyroscope with robust drive mode and its implementation. The proposed design utilizes dynamic amplification of torsional oscillations instead of resonance in drive oscillator, which essentially is a 2-DOF oscillator, to eliminate the requirement of mode-matching. The frequency response of drive oscillator has two resonance peaks and a flat region between the peaks, where the amplitude is less sensitive to ambient damping resulting in robust drive mode. The frequency response of 1-DOF sense oscillator has one resonance peak which is designed to coincide with the flat region to minimize the effects of change in geometry and material properties of the device, due to inevitable fabrication imperfections, on the device performance. The design equations of electrostatic moment, moments of inertia, and spring constants are presented. The concepts of anti-resonance and zero-phase frequencies are introduced. The design is then implemented using SU-8 based UV-LIGA process having 8 µm thick Ni---Fe as the key structural layer. The fabricated device is also characterized for amplitude and phase spectral responses using Polytec MSA-500 Micro System Analyzer. The resonance frequencies of drive oscillator are observed at about 5.66 and 13.11 kHz against the design values of 5.37 and 13.18 kHz, respectively. The resonance frequency of sense oscillator is found at about 10.05 kHz against the design value of 10 kHz. The anti-resonance and zero-phase frequencies are observed at about 10.08 and 9.97 kHz, respectively against the design value of 10 kHz.