A fast alignment algorithm based on inertial frame for marine SINS

A fast alignment algorithm based on inertial frame is proposed in this paper. Firstly, a third-order leveling loop is used for fine leveling alignment to establish a level coordinate frame. Secondly, the property that the projection of the gravitational vector in level coordinate frame is unrelated to heading angle is used to calculate the projection of the gravitational vector in body inertial coordinate frame. Thirdly, the projection of the gravitational vector is smoothed through weighted average algorithm, so that the fast alignment based on inertial frame is completed. Finally, the simulation and mooring test validate the speedability and accuracy of this fast alignment algorithm. The results show that the fast initial alignment algorithm can achieve the medium accuracy in 6 minutes. It fulfills the accuracy requirement for the medium accuracy marine SINS.