In-Motion Alignment Method of SINS Under the Geographic Latitude Uncertainty

Initial alignment is vital to the strapdown inertial navigation system (SINS), and the in-motion initial alignment is a critical stage for underwater vehicles. In order to realize the in-motion alignment of the SINS under the geographic latitude uncertainty, we propose a latitude estimation method based on wavelet filtering. The external reference velocity is introduced, and the parameter adjustment strategy of the compass alignment control loop under different maneuvering modes is designed to improve the alignment accuracy. Firstly, the influence of line motion on the compass alignment is analyzed, and the in-motion compass alignment scheme of SINS based on the assistance of the external velocity is designed. Then, the error analysis is carried out by using the transfer function of the compass alignment loop. Moreover, the influence of different maneuverability on alignment accuracy is discussed. Finally, the setting strategy of control parameters of the compass alignment loop under different maneuvering modes is put forward. Simulation results are reported to validate the latitude estimation and in-motion alignment performance of the proposed method.