Abstract: In order to achieve higher alignment precision, stronger numerical stability and lower computational cost for nonlinear alignment of strapdown inertial navigation system (SINS) on moving base, a scheme of 5th-degree dimensionality reduction SR-CKF nonlinear alignment is proposed，which combines 5th-degree cubature Kalman filter (CKF), dimensionality reduction algorithm, multiple discretization, and square root(SR) filter. A nonlinear-linear separation system model is established, and the dimensionality reduction algorithm is introduced to reduce the calculated amount. A multiple discretization and time update filter framework is designed to improve the approximation accuracy. The 5th-degree dimensionality reduction SR-CKF is deduced to improve the numerical stability. The features of the conventional 3rd-degree SR-CKF, 5th-degree CKF and the proposed algorithm are compared. The experimental results show that the proposed method has a high alignment precision, strong numerical stability and little calculated amount, which meets the application requirements.

Key words: ordnance science and technology, cubature Kalman filter, dimensionality reduction, square root filter, multiple discretization