SINS/GPS/SS reduced-order kalman filter design based state decoupling for space application

The integrated navigation Kalman filter of strapdown inertial navigation system/Global Positioning System/star sensor (SINS/GPS/SS) with pesudorange and quaternion as observation information, has been researched for space autonomous navigation. To improve the real-time working performance, the reduced-order Kalman filter based state decoupling is put forward. With the hypothesis that SS precision is stable, the quaternion error state in SINS/GPS/SS filter with the pseudorange and quaternion as the observation information would be small and could be neglected in the velocity error loop of filter model. Thus quaternion error state would be decoupled with the state of velocity and position error. The original SINS/GPS/SS integrated navigation filter model would be separated into two independent subfilters, which are special for quaternion error state and velocity/position error states. The dimension is decreased from 18 of original SINS/GPS/SS filter to 7 and 11 of two reduced-order filters. The simulation results shows that filter performance of the reduced-order filters is almost same as the original SINS/GPS/SS filter´s while the calculation is decreased obviously. The reduced-order plan is verified to be feasible.