Abstract:A modal frequency analysis method is proposed in this paper to solve the problem of time consumption in the iterative design of the operating modal frequency of an eight-mass MEMS gyro with a complex structure. First, according to the characteristics that the eight-mass MEMS gyro harmonic oscillator is composed of lumped mass connected by unidirectional stiffness flexible beam in a rotationally symmetric arrangement, it is equivalent simplified into a mass-spring model. Second, the Lagrange equation is used to establish the dynamic equation describing the mass-spring equivalent model. Third, considering the characteristics of the working mode shapes of the eight-mass MEMS gyro, the dynamic equation is specifically simplified, the mass matrix and stiffness matrix are extracted, and the eigenvalues of the determinant formed by the mass matrix and stiffness matrix are solved. The eigenvalue that conforms to the mode shape characteristics of the working mode is the required working mode frequency. Finally, the frequency deviation is found to be 12.8%, which verifies the reliability of the established frequency analysis model. Compared with the complex modeling process required by finite element simulation, This modal frequency analysis method only needs the stiffness of the flexible beam and the mass of the mass block to calculate the frequency of the working mode, and thus can effectively improve the design efficiency of an eight-mass MEMS gyroscope.