The Research Of Spacecraft Autonomous Navigation Algorithm Based On The X-ray Pulsars

An X-ray pulsar-based navigation is a new kind of celestial navigation technology, which uses X-ray pulsar as its navigation source. It can provide navigation parameters, such as position and velocity relative to the reference frame of time and space with high precision for spacecrafts. It has high reliability, high precision, strong autonomy, etc, and has become an important development direction and a hot research subject in the spacecraft autonomous navigation file d, especially for spacecrafts probing the deep space. In this paper, we research the X-ray pulsar-based spacecraft autonomous navigation algorithm under the background of pulsar navigation so as to improve the autonomous navigation precision of the spacecraft.The mathematical model associated with X-ray pulsar navigation is studied firstly. The time-space model is elaborated. The pulse phase time model is introduced. The pulse propagation model is established. The navigation system models are researched, including the orbit dynamic model and measurement model. All these analysis provide a theoretical basis for the simulation research of X-ray pulsar-based spacecraft autonomous navigation algorithm.In order to reduce the impact of the model error on the aut onomous navigation accuracy, an innovative navigation algorithm, namely, Nonlinear Predictive Filter(NPF) is proposed. It can estimate system model error in time, and then modify the navigation system model with uncertainty. Simulation results demonstrate that this algorithm could obtain higher navigation precision than both Extended Kalman Filter(EKF) and Unscented Kalman Filter(UKF).In order to weaken the influence of the pulsar direction error on the autonomous navigation accuracy, an original navigation algorithm based on the Augmented State Unscented Kalman Filter(ASUKF) and Online Pulsar selection is put forward, it is on the basis of the existing ASUKF algorithm. On the one hand, this algorithm can effectively reduce or even eliminate the pulsar direction error’s influence on the navigation precision; on the other hand, it could choose the optimal combination of pulsar online, Thus it can improve the navigation accuracy. Simulation results demonstrate that this algorithm could acquire higher navigation precision than the conventional ASUKF algorithm.Finally, the spacecraft autonomous navigation simulation system is stud ied. The overall scheme of navigation simulation system is designed based on the combination of MATLAB and STK(Satellite Tool Kit). The design and implementation of some key modules of navigation simulation system is described in detail, and the simulation system’s performance is tested.