Adaptive Control for MEMS Gyroscopes

This report presents a new adaptive operation strategy for MEMS z-axis gyroscopes. Specifically, a unified methodology is proposed for designing and analyzing the performance of a control algorithm that can identify and, in an adaptive fashion, compensate for most fabrication defects and perturbations affecting the behavior of a MEMS z-axis gyroscope. Dynamic analysis of typical MEMS gyroscopes shows that fabrication imperfections are a major factor limiting the performance of the gyroscope. However, the motion of a conventional mode-matched z-axis gyroscope does not have sufficient persistence of excitation and, as a result, all major fabrication imperfections cannot be identified and compensated for in an on-line fashion. The proposed adaptive control algorithm with velocity estimation, which operates with only measurements of the x and y positions of the proof mass, estimates the component of the angular velocity vector, which is orthogonal to the plane of oscillation of the gyroscope (the z-axis) and the linear damping and stiffness model coefficients in an on-line fashion. The convergence and resolution analysis presented in report showed that the proposed adaptive controlled scheme offers several advantages over conventional modes of operation. These advantages include a larger operational bandwidth, absence of zero-rate output, self-calibration and a large robustness to parameter variations, which are caused by fabrication defects and ambient conditions.