A new invariant extended Kalman filter based initial alignment method of SINS under large misalignment angle

For the initial alignment of strapdown inertial navigation system (SINS) under the condition of large azimuth misalignment, a high-precision and fast initial alignment method is proposed. Firstly, in the Lie group space, the system matrix F and the measurement matrix H, which are relatively independent of the state estimate, are derived, and the invariant extended Kalman filter (INEKF) architecture. The INEKF not only eliminates the influence of the current state estimation error on the system matrix F and the measurement matrix H, but also suppresses the positive feedback and inconsistency problems that occur in the state update process of EKF. Then, the SINS initial alignment model is established based on INEKF. Finally, simulation results show that this method can effectively improve the speed and accuracy of the initial alignment, especially under the condition of a large misalignment angle, the alignment speed and accuracy are also greatly improved.