The initial attitude error is challenging to satisfy the requirements of the linear model due to the complex nature of the ocean environment. This presents a challenge in the transfer alignment of the ship. In order to enhance the precision and velocity of ship transfer alignment, as well as to streamline the alignment processes, this paper proposes a transfer alignment methodology based on the Earth-Centered Earth-Fixed (ECEF) frame special Euclidean group (SE(3)) matrix Lie group. After introducing the two navigation states, velocity and attitude, from the ECEF frame into SE(3), the nonlinear inertial navigation system error state model and its corresponding measurement equations are derived based on the mapping relationship between the Lie groups and Lie algebra. The method effectively solves the error problem due to linear approximation in the traditional transfer alignment method, and applies to misalignment angles of arbitrary scale. The simulation results verify the effectiveness and rapidity of the proposed alignment method in the case of arbitrary misalignment angles.

At present, large and medium-sized ships are usually equipped with two or more sets of inertial navigation systems, but the inertial navigation systems operate independently of each other, and this approach only improves the reliability of the navigation information, and does not improve the accuracy of the navigation information. Aiming at the above problems, this paper proposes a dual-IMU joint modulation scheme, which ensures that there is an IMU in pause at any moment by reasonably designing the rotation strategy of the two sets of IMUs, so as to combine the data of the two IMUs in the time sequence. The scheme utilizes the symmetry of the rotational position to eliminate the error, and at the same time avoids the coupling error caused by the rotational motion of the IMUs, reduces the periodic error, and improves the navigation accuracy. Semi-physical simulation test results show that the improved joint modulation scheme has superior modulation effect on the device errors of inertial devices compared with the traditional rotational modulation scheme.