Abstract
A digital mode-matching control system based on feedback calibration, where two pilot tones are applied to actuate the sense mode by the robust feedback controller, is presented for a MEMS gyroscope in this paper. A dual-mass decoupled MEMS gyroscope with the integrated electrostatic frequency tuning mechanisms, the quadrature correction electrode, and the feedback electrode is adopted to implement mode-matching control. Compared with the previous mode-matching method of forward excitation calibration, the proposed mode-matching scheme based on feedback calibration has better adaptability to the variation in the frequency of calibration pilot tones and the quality factor of the sense mode. The influences of calibration pilot tone frequency and the amplitude ratio on tuning performance are studied in theory and simulation. The simulation results demonstrate that the tuning error due to the amplitude asymmetry of the sense mode increases with a frequency split between pilot tones and the drive mode and is significantly reduced by the amplitude correction technology of pilot tones. In addition, the influence of key parameters on the stability of the mode-matching system is deduced by using the average analysis method. The MATLAB simulation of the mode-matching control system illustrates that simulation results have a good consistency with theoretical analysis, which verifies the effectiveness of the closed-loop mode-matching control system. The entire mode-matching control system based on a FPGA device is implemented combined with a closed-loop self-excitation drive, closed-loop force feedback control, and quadrature error correction control. Experimental results demonstrate that the mode-matching prototype has a bias instability of 0.63°/h and ARW of 0.0056°/h1/2. Compared with the mode-mismatched MEMS gyroscope, the performances of bias instability and ARW are improved by 3.81 times and 4.20 times, respectively.
Highlights
Over recent years, MEMS-based gyroscopes have found widespread application in the automotive and consumer fields, including rollover detection and electronic stability control, gaming consoles, and image stabilization in digital cameras [1,2,3]
A variety of means have been proposed to improve the accuracy of MEMS gyroscopes, such as array gyroscopes with multimasses [7], 3-D fabrication techniques with high-aspect ratio and effective volume utilization [8], digital control method based on ΔΣ technology [9], and mode-matching technology [1]
This paper presents a digital mode-matching control loop based on feedback calibration for MEMS gyroscopes
Summary
MEMS-based gyroscopes have found widespread application in the automotive and consumer fields, including rollover detection and electronic stability control, gaming consoles, and image stabilization in digital cameras [1,2,3]. A variety of means have been proposed to improve the accuracy of MEMS gyroscopes, such as array gyroscopes with multimasses [7], 3-D fabrication techniques with high-aspect ratio and effective volume utilization [8], digital control method based on ΔΣ technology [9], and mode-matching technology [1]. Mode-matching technology is widely concerned and becomes one of the most promising approaches to improve the accuracy of MEMS gyroscopes. Under mode-matched conditions, the sense mode is designed to own the same (or nearly the same) resonant frequency with the drive mode. It is hard to completely match the resonant frequencies between two modes through structural design due to the fabrication imperfections. Various approaches have been developed to reduce the frequency mismatch between two resonance
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