Application of the 2nd-order Smooth Variable Structure Filter algorithm for SINS initial alignment

This paper is focused on the application of 2nd-order Smooth Variable Structure Filter (SVSF) algorithm in the initial alignment of Strapdown Inertial Navigation System (SINS), which is used to achieve robust and precise alignment results in large azimuth misalignment angle. Normally, the SVSF method requires the system to be observable and controllable, motivated by this, a combined alignment structure is proposed based on the Kalman type filter alignment method and gyrocompass alignment method firstly and the 2nd-order SVSF method is used to estimate the misalignment angles in the process of the combined alignment. Compared to the conventional alignment estimation method, the simulation results show that the 2nd-order SVSF alignment method could gain a more stable and accurate misalignment angle.