The Research Of Filtering Method For X-ray Pulsar Autonomous Navigation Positioning

The autonomous navigation is the key technology to realize the autonomous management of spacecraft and improve its on-orbit survivability.As a newly emerging method of autonomous celestial navigation for spacecraft,X-ray pulsar navigation can provide spacecraft with abundant navigation information,such as position,velocity,attitude and time.Among them,the high-precision position information is the main factor to ensure the smooth progress of space missions.Combining the measurement information of the pulsar with the orbital dynamics equation,the accurate positioning of the spacecraft can be achieved by the advanced filtering algorithm.However,the pulse radiation signal is so very weak that it needs to be accumulated for a long time to obtain high-precision measurement information.Which leads to the pulsar navigation with longer filtering cycle and poor real-time performance.The pulsar/Doppler integrated navigation can provide high precision for the spacecraft navigation information in real time,but the spectral distortion will cause a large deviation on Doppler velocity,which lead to a sharp decline in filtering accuracy and seriously affect the positioning accuracy of the integrated navigation.In addition,the instability of the pulse radiation and the pulsar directional errors affect the statistical characteristics of the pulsar measurement noise,which results in the decrease or even divergence of the EKF filtering accuracy in the pulsar navigation and positioning system.In this paper,based on the basic principle of autonomous navigation and positioning of X-ray pulsars,some key problems in the filtering algorithm of pulsar navigation positioning mentioned above are researched to realize the accurate positioning of spacecraft.The main contents of the dissertation are as follows:(1)In order to reduce the effect of spectral distortion on Doppler velocity and improve the navigation precision,the residual detection method is introduced into the integrated navigation filtering process in this paper and the Doppler/pulsar integrated navigation filtering method based on residual detection is proposed.The residual of Doppler velocity measurement is detected to determine whether the solar spectrum is distorted,and only the measurement of pulsar is adopted as the navigation measurement when the solar spectrum is distorted.Conversely,both the Doppler velocity and the pulsar measurement are utilized as the navigation measurement.Then the Doppler velocity error is corrected by the pulsar observation to obtain higher positioning accuracy.(2)To solve the problem of the EKF filter in the pulsar navigation positioning system when the statistical characteristics of the pulsar measurement noise can not be fully known,an adaptive filtering method based on EMD_EKF is proposed.By means of empirical mode decomposition,the high frequency noise is separated from the measurement information of pulsar.Then the noise variance is estimated to correct the relevant parameters of the EKF algorithm in real time,so as to realize the precise positioning of spacecraft.Finally,this paper use STK software to acquire the nominal orbit data of spacecraft,and the proposed method is simulated and validated by MATLAB simulation platform.