Abstract: The traditional strapdown inertial navigation algorithm model is nonlinear, the attitude, speed and position need to be calculated step by step, and the accuracy of the algorithm is low under high dynamic conditions. To solve the problems, a novel strapdown inertial navigation algorithm based on pseudo linear model in the geographic coordinate system is proposed. A new system model of unitive navigation vector is designed with pseudo linear model and its analyzing methods, after each part of the traditional SINS algorithm has been converted to pseudo linear form. Then the high order numerical integration algorithm is used to improve the accuracy of navigation vector updating, and an SINS algorithm in geographical coordinate system based on pseudo linear model is obtained. Finally, a series of flight simulations are carried out to evaluate the accuracy of the algorithm. Compared with the traditional SINS algorithm, the pseudo linear algorithm accuracy is improved by two orders of magnitude in high dynamic maneuver conditions, while its navigation error is less than 1/5 of the traditional algorithm in the spinning projectile simulation. The proposed pseudo linear SINS algorithm is simple in structure, can complete the navigation vector update by using one update loop, and has higher algorithm accuracy under the condition of high dynamic and large maneuver. Therefore, it has certain reference value for the research and engineering application of SINS algorithm.

Key words: Pseudo linear model, Strapdown inertial navigation system (SINS), Quaternion, High accuracy navigation