Research on Two-order SINS Coarse Alignment Method assisted by DVL in Quasi-static

Strapdown Inertial Navigation System (SINS)/Doppler Velocity Log (DVL) navigation system provides positioning services for Unmanned Underwater Vehicle (UUV). The positioning precision of the system is directly impacted by the accuracy of SINS alignment. However, the ocean current causes the UUV to have additional acceleration when the UUV is started in quasi-static state. The accelerometer output no longer equal to the standard gravity acceleration, reducing the coarse alignment accuracy. In order to solve this problem, a two-order improved dual-vector attitude matrix decomposition-based alignment method based on DVL velocity assistance is proposed in this paper. In this method, the DVL output velocity is used to judge the time interval of the carrier without linear interference acceleration. The second-order coarse alignment is used to compensate the Coriolis acceleration caused by the carrier velocity. Three different sets of trajectory experiments were used to validate the effectiveness and applicability of the method proposed in this paper. The experimental results show that the proposed method improves the alignment accuracy compared with the Dual-vector Attitude matrix decomposition-based alignment method, which proves that the proposed method can improve coarse alignment performance.