A analytic coarse alignment method for SINS based on two-step recursive least squares

In order to reduce the coarse alignment time of strapdown inertial navigation system(SINS), an analytic initial coarse alignment method is proposed based on two-step recursive least squares estimation. The initial attitude matrix which represents the attitude and heading of SINS is estimated by two steps in the method. Firstly, some elements in the initial attitude matrix are estimated by an accelerometer measurement based on recursive least squares algorithm; secondly, the remainder elements in the initial attitude matrix are estimated by a gyro measurement and the estimated elements in the first step; and then, the system initial alignment is completed by solving the initial attitude matrix. Finally, tests for the proposed method are carried out under the different conditions of SINS, such as simulation, laboratory static and mooring on the sea. The results show that rapidity of the coarse alignment increases under the premise in alignment accuracy.