Kevin Townsend

Precision mode matching of MEMS gyroscope by feedback control

This paper reports on mode matching of a MEMS gyroscope using simplified displacement feedback and reduces the frequency split between the two modes to less than 0.01 Hz. Mode matching is shown to improve the gyro performance significantly and reduce the bias stability from 3 degree/hour to 0.5degree/hour. The displacement feedback matching scheme provides an in situ matching control that may augment the generally coarser electrostatic tuning method. The control has been realized in a high performance DSP based rate gyroscope control system and experimental results show the effectiveness of the control algorithm.

Control Scheme to Reduce the Effect of Structure Imperfections in a Rate Integrating MEMS Gyroscope

In this paper, a control scheme is presented for a rate integrating microelectromechanical system ring gyroscope that reduces the effects of structural imperfections on the precession of an ellipse used to describe the structural vibration of the gyroscope. Modeling is provided that demonstrates the potential increase in gyroscope measurement accuracy on implementation of the control scheme. Furthermore, the description of the gyroscope dynamics used provides an alternative description of the effect of drive mistuning. Finally, experimental results are provided that demonstrate the viability of the proposed control scheme.

A digital signal processing-based control system for a micro-electromechanical systems vibrating gyroscope with parametric amplification and force rebalance control:

This article reports a digital signal processing-based digital implementation of a micro-ring gyroscope control system that can be programmed to operate in open loop with parametric amplification or closed loop with force rebalance control according to bandwidth and dynamic range requirements. Parametric amplification is directly applied to the secondary mode and amplifies the Coriolis response by an order of magnitude. In order to improve the dynamic range and bandwidth performance of the gyroscope, force rebalance control loops are designed for the vibrations both in-phase and in quadrature with the Coriolis response. Experimental results show parametric amplification of the Coriolis response by a factor of 11 and correspond to an improvement in the signal-to-noise ratio by a factor of 9.5. The effectiveness of the force rebalance control is shown experimentally, and both the measurement bandwidth and the dynamic range have increased beyond the test capability of the rate table.

Control scheme for a rate integrating MEMS gyroscope

Rate integrating gyroscopes measure angular rate by measuring the change in energy transfer between two orthogonal modes of vibration as rate is applied. Although these gyroscopes have the potential for high accuracy due to their direct measurement of angle, they are often hindered by material imperfections, the most significant of which are perturbations in stiffness within the material structure. This paper describes a control scheme for a rate integrating ring gyroscope that can limit the effect of these imperfections, providing experimental results to demonstrate the validity of the scheme.