Design and analysis of a z-axis tuning fork gyroscope with guided-mechanical coupling

This paper presents design and analysis of a z-axis tuning fork gyroscope. The sensor is designed to reduce noises and improve the sensitivity by using a drive coupling spring in the lozenge shape. The in-phase sensing mode is suppressed by using a self-rotation ring. The designed sensor prioritizes anti-phase driving and sensing modes. The frequencies of anti-phase driving and sensing modes are far from those of parasitic ones. The design also enables the sensing mode to decouple from the driving one, which is considered to decrease vibration-induced error. The proposed sensor structure is analyzed by finite element method. The simulated frequencies of the driving and sensing modes are 9.9 and 10.0 kHz, respectively, which show the bandwidth of sensor of 100 Hz. The frequency difference between the driving and sensing modes and the parasitic ones is obtained to be 50 %. The optimized gap between electrodes leads to the determination of the number of the sensing capacitor fingers and consequently the suitable dimension parameters of the whole device. The sensor performance in the time domain and the frequency domain having the transient response to a given rotation rate is also simulated showing the linear dependence of capacitance change on angular velocity. As a result, the sensitivity of the sensor is evaluated to be 11 fF/°/s.