One new onboard calibration scheme for gimbaled IMU

Keeping the gimbals unlocked and rotating the gimbals continuously, the measured gimbal angles can be used to calibrate gyro parameters and case misalignments as the IMU is mounted on a gyro-stabilized platform. Because the gyro errors and case misalignments propagate nonlinearly in gimbal angles error model, a nonlinear estimation filer, spherical simplex unscented Kalman filter (SSUKF), is adopted to deal with this problem. Besides, the parameters' observability is analyzed by the singular value analysis of the observability matrix and the theory of relative output sensitivity and a continuous calibration scheme is established. Simulation for the proposed calibration scheme is conducted and the sensitivity to environment disturbances is analyzed. It is shown that the proposed method can calibrate onboard gimbaled IMU with high precision and proves practical in dealing with environment disturbances.