A dual-mass fully decoupled MEMS gyroscope with optimized structural design for minimizing mechanical quadrature coupling

Mechanical quadrature coupling is one of the main sources of zero-rate output in microelectromechanical system (MEMS) gyroscope, which limits the further improvement of gyroscope performance. This paper reports a dualmass MEMS tuning fork gyroscope based on fully decoupled structure. The theoretical analysis and finite element method (FEM) simulation are performed to identify the sources of the mechanical quadrature error in detail and to find ways to optimize the structural design of MEMS gyroscope. The results show that reducing the quadrature coupling stiffness of local sensing components is a key factor in minimizing the overall gyroscope quadrature error. By deliberately optimization of the geometry of the sensing components including sense frame and the drive springs closed to the sense frame, the quadrature induced deformation of sense electrode can be reduced from 160 nm to 5.1 nm with a driving displacement of 1 mu m based on FEM simulation. The equivalent angular rate output caused by quadrature coupling of each sense electrode can be reduced from 3960 degrees/s to 60 degrees/s. The optimized gyroscope operates in split-mode with open-loop readout. The measured scale factor of gyroscope is 90.46 LSB/(degrees/s) with a non-linearity of 810 ppm in the full scale range of +/- 300 degrees/s. The measurement result root 305;shows a bias instability of 8.9 degrees/h and an angular random walk (ARW) of 0.74 degrees/ h at room temperature, respectively. The proposed approach of structural improvements can be used to reduce the quadrature error of the gyroscope in processing tolerances.