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We present a long-term bias drift compensation algorithm for high quality factor (Q-factor) MEMS rate gyroscopes using real-time temperature self-sensing. This approach takes advantage of linear temperature dependence of the drive-mode resonant frequency for self-compensation of temperature-induced output drifts. The approach was validated using a vacuum packaged silicon Quadruple Mass Gyroscope (QMG), with signal-to-noise ratio (SNR) enhanced by isotopic Q-factors of 1.2 million. Owing to the high Q-factors, measured frequency resolution of 0.01ppm provided a temperature self-sensing precision of 0.0004°C, on par with the state-of-the-art MEMS resonant thermometers. The real-time self-compensation yielded a total bias error of 2°/h and a scale-factor error of 700ppm over temperature range of 25–55°C. The presented approach enabled repeatable long-term rate measurements required for MEMS gyrocompassing applications with a milliradian azimuth precision. [ABSTRACT FROM AUTHOR]

• Structural asymmetries of the vibratory gyroscope are induced mainly by fabrication errors. • Structural imperfections limit the sensor performance by affecting the signal-to-noise ratio, resolution, zero rate output and bias stability. • Mechanical ablation of interconnecting spokes in concentric ring suspension of a gyroscope enabled coarse (>50 Hz) tuning and fine-tuning (<1 Hz) of resonant frequencies. • Mechanical trimming allows for permanent tuning of the gyroscope's vibratory modes without introducing additional noise. • Electrostatic tuning allows for gyroscope frequency split reduction to the level of mHz after packaging of the device. This paper reports mechanical ablation techniques for permanent frequency tuning of the primary wineglass modes in planar gyroscopes with concentric ring suspension. Three different approaches for frequency tuning are discussed: (1) selective mass removal, (2) stiffness reduction via thinning of suspension elements, and (3) stiffness reduction by removal of interconnecting spoke elements between concentric rings. A predictive tuning algorithm is developed for identification of ablation locations to guide the trimming process. A dual-mass Dynamically Amplified Gyroscope (DAG) design is used to demonstrate the tuning approach. It is shown that introduction of "side-spokes" to the concentric ring system of DAG enables coarse (> 50 Hz) tuning, as well as fine-tuning (< 1 Hz) of resonant frequencies, which is performed by means of mechanical ablation with focused ion beam (FIB). Finally, a comparison of the sensor noise characteristics using active electrostatic tuning and mechanical ablation is presented. [ABSTRACT FROM AUTHOR]

This paper presents a study on dynamics of a dual-mass MEMS vibratory gyroscope in presence of fabrication imperfections and reports a method for precision electrostatic frequency tuning of the operational modes. A number of multi-mass MEMS gyroscopes have emerged in recent years pursuing different goals, such as dynamically balanced structure, increased bandwidth, and dynamic amplification. Along with many perceived advantages of multi-mass devices, several challenges associated with mode-matching in a system with increased number of degrees-of-freedom (DOF) have to be considered. This work shows that it is possible to apply the DC tuning techniques, similar to tuning a conventional single-mass gyroscope, to achieve the precision tuning in a dual-mass sensor, without losing advantages of increased DOF of the system. The presented frequency trimming technique is based on assessing the modes mismatch and cross-coupling between modes by means of fitting the experimental frequency response curves to the analytical solutions of the dual-mass system in presence of imperfections. The tuning algorithm involves two steps. First, the stiffness mismatch along the two axes and the anisoelasticity angles α and β are identified, then the tuning DC voltages for modification of diagonal, off-diagonal, and coupling terms in the stiffness matrix are chosen. The method of electrostatic tuning was validated through the experimental characterization of a dual-mass dynamically amplified gyroscope, where the coupling between the two operational modes was minimized and frequency split was reduced from 26 Hz down to 50 mHz, resulting in 17.5× increase in the gyroscope scale factor and significantly improved noise characteristics. The presented electrostatic compensation method is suitable for both off-line and on-line calibration. [ABSTRACT FROM AUTHOR]

Abstract: We report detailed characterization of a vacuum sealed rate integrating silicon MEMS gyroscope. The new gyroscope utilizes geometrically symmetric, dynamically balanced quadruple mass architecture, which provides a combination of maximized quality (Q) factors and isotropy of both the resonant frequency and damping. The vacuum sealed SOI prototype with a 2kHz operational frequency demonstrated virtually identical X- and Y-mode Q-factors of 1.2 million. Due to the stiffness and damping symmetry, and low energy dissipation, the gyroscope can be instrumented for direct angle measurements with fundamentally unlimited rotation range and bandwidth. Experimental characterization of the mode-matched gyroscope operated in whole-angle mode confirmed linear response in a ±450°/s range and 100Hz bandwidth (limited by the experimental setup), eliminating both bandwidth and range constraints of conventional open-loop Coriolis vibratory rate gyroscopes. [Copyright &y& Elsevier]