Simulation And Analysis Of The Filters For Spacecraft Navigation Based On X-ray Pulsars

With the advantages of high reliability, good autonomy, high precision and wide applicability, X-ray pulsar-based spacecraft navigation comes to be a new kind of autonomous navigation technology with high potential. It is not only suitable for the deep space exploration but also helpful to the navigation of earth-orbit spacecrafts. At present, the countries advanced in aerospace engineering are competitively making research in this aspect. This article researches on the theories, system structure and working process of pulsar navigation, on the basis of which a simulation analysis is carried out by adopting two kinds of filter in order to improve the precision of pulsar navigation.First of all, coordinate systems and time systems are introduced, and phase-time model of pulsar is analyzed. Secondly, the transformation equation of proper time and coordinate time, and that of time-of-arrival(TOA) is presented. Then the general methods in pulsar navigation are introduced, and the pulsar navigation principle on the basis of delta-correction method is explained in detail. After that, based on the pulsar navigation principle, the structure and the working process of pulsar navigation system is discussed in detail. Then, the simulation model of both EKF and UKF filter algorithms are established and a unified interactive environment of simulation is set up. Finally, on the basis of the dynamic model of spacecraft orbit, the performance of EKF and that of UKF in the pulsar navigation is analyzed and compared simulatively.The simulation result shows that with the pulsar TOA precision being 1μs and the direction precision of pulsars0.0001arcsec , the precision of navigation can achieves magnitude of 10m. In addition, the article, from aspects of the pulsar TOA precision, the direction precision and the filter period, makes an error analysis of the simulation result, the result of which is shown as follows: navigation precision has a somewhat direct ratio with TOA precision; with the direction precision of pulsars below 0.0001arcsec , navigation precision drops drastically; when the filter period increases, navigation precision by using EKF algorithm also tends to a marked decline, while there is little influence on the case of using UKF. Finally, the performance of EKF and that of UKF filter algorithms is compared from aspects of filter precision, running time and the algorithm convergence. It turns out that although UKF algorithm needs a longer running time, it can achieve a higher navigation precision with a better convergence.X-ray pulsar-based spacecraft navigation is a kind of autonomous navigation technology with high potential.The result of this research has significance in the further research of system structure, working process and filter method of pulsar navigation.