Self-alignment method for strap down inertial navigation system in moorage

In order improve the performance of Strapdown Inertial Navigation System (SINS) alignment in moorage, a novel alignment method is proposed. With the aid of a cascade low-pass FIR filter, the gravity vector is separated from the measurements of accelerometers due to the high frequency characteristic of the disturbance accelerations and the low frequency characteristic of the gravity vector. Two non-collinear velocities both in the inertial frame and in the concretionary are integrated by the gravity vector and the cosin matrix between the two frames is calculated. With the other matrix which can be calculated easily, the alignment is accomplished. Results of experiment show that the accuracy of the alignment method proposed in this paper converges much faster than the traditional alignment methods. However, the new method is a open-loop method, thus the precision is not significantly improved.