Algorithm of the autonomous initial alignment of sins with sequential filtering

An algorithm for an autonomous initial alignment of a strapdown inertial navigation system on a fixed or limitedly movable base is proposed and considered. It sequentially uses two Kalman averaging filters in. The first one determines one column of the directing cosines matrix (DCM) between the axes of the associated with the object and the geographical accompanying bases by the signals of the accelerometers. The second filter determines the second column of the matrix based on the gyroscope signals and the obtained estimates of the direction cosines. The third column is determined from known ratios. From the resulting DCM, the heading, pitch and roll angles are determined. Information signals for solving the problem are obtained by averaging a small interval (5 s) at the end of the Kalman filter transition process. This allows minimizing errors from changing the position of the object during the measurement time, which can reach tens of minutes. The advantage of the algorithm is the independence of errors from the object heading. It is shown that pre-smoothing of signals improves accuracy. The algorithm makes it possible to determine the orientation angles, and then the direction cosines at a measurement time insufficient to complete the transient evaluation process by the Kalman filter. The conducted field experiments confirm the good characteristics of the alignment on a fixed and vibrating base, achieved using the algorithm.