Noise analysis of mode matched vibratory gyroscopes

MEMS (micro-electromechanical system) vibratory gyroscopes have attracted a lot of interest recently and these gyroscopes made their way through portable devices and smart phones. However, their performance is not enough to cope with the demanding requirements of applications such as dead reckoning. Mode-matched gyroscopes can be a solution for this problem. Various mode-matched gyroscope architectures have been proposed and their noise performances have been analyzed in detail. However, in most of these analyses zero-rate output was considered and the noise analysis for dynamic cases were ignored. In this paper, we demonstrate the noise analysis of mode-matched vibratory gyroscope using the power spectral density (PSD) and the Allan deviation methods while in rotation. We show that for mode-matched gyros the noise performance of a rotating gyro can be significantly different from that of a gyro that does not experience any rotation. We also show that this difference is due to the coupling between the drive and sense systems via Coriolis force. This sets a fundamental limit for the noise performance of mode-matched vibratory gyroscopes where ARW (angle random walk) increases proportionally with the rotation rate for the open loop and the force to rebalance operation modes.