Electrostatic compensation of structural imperfections in dynamically amplified dual-mass gyroscope

• Published in: Sensors and actuators. A. Physical. 2018-06, Vol.275, p.99-108
• Main Authors: Efimovskaya, Alexandra, Wang, Danmeng, Lin, Yu-Wei, Shkel, Andrei M.
• Format: Article
• Language: English
• Subjects: Amplification; Anisoelasticity; Compensation; Coupling; Cross coupling; Defects; Degrees of freedom; Dual-mass system; Electrostatics; Fabrication imperfections; Frequency response; Frequency split; Gyroscopes; Materials elasticity; Mathematical analysis; MEMS gyroscope; Precision electrostatic tuning; Stiffness matrix; Tuning
• ISSN: 0924-4247; 1873-3069
• DOI: 10.1016/j.sna.2018.03.001

•MEMS gyroscope design utilizing coupled masses for dynamic amplification is shown.•Fabrication errors result in mode-splitting and reduction in amplificationfactor.•Precision electrostatic frequency tuning in a dual-massgyroscope is demonstrated.•Analytical model and experimental data are used toestimate the system parameters.•Dynamically amplified gyroscope is used for verification ofthe tuning algorithm. 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.