In-Motion Initial Alignment Method for LDV-Aided SINS Based on Adaptive Unscented Quaternion H-infinite Filter

With the advantages of high velocity measurement accuracy and fast dynamic response, the laser Doppler velocimeter (LDV) is expected to replace the odometer (OD) to be combined with a strapdown inertial navigation system (SINS) to form a higher precision integrated navigation system. Since LDV has higher velocity measurement accuracy and data update frequency than OD and Doppler velocity log, LDV is used for the first time to aid SINS in in-motion alignment in this paper. Considering that some approximation used in the alignment model, the uncertainty noise of the sensors during the motion process and the unknown noise parameters during the filter process, an adaptive unscented quaternion H-infinite estimator (AUSQUHE) is proposed in this paper. The proposed AUSQUHE method has high robustness since it combines the advantages of unscented quaternion estimator and H-infinite filter. And the adaptive threshold of H-infinite filter and the adaptive measurement noise covariance matrix are introduced to make the filter adapt to the environment change and accelerate the convergence of errors. The performance of the proposed method is verified by a vehicle field test with normal LDV signal and a vehicle test with LDV signal disturbed by the noise. The results show that the proposed method has higher alignment accuracy, faster convergence speed and stronger robustness than four other compared methods.