The Method Of X-ray Pulsar Autonomous Navigation

X-ray pulsars are similar to natural beacons. Its extensive distribution and stability of signal makes it as extremely promising natural beacon for autonomous navigation. In recent years, XNAV(X-ray pulsar-based Navigation) has become one of the highlights in the research of space autonomous Navigation. The plans of autonomous Navigation based on X-ray pulsar are carried out one after another. The main contents are as follows.The basic theories of X-ray pulsar navigation are researched. This paper introduces the basic characteristics of pulsars and space-time frame of XNAV. The basic processing methods of X-ray pulsar navigation and the basic component of navigation system have been discussed. The methods of positioning navigation and synchronous timing based on X-ray pulsar are studied, including attitude navigation.The methods of phase estimation for pulsar signal and related processing methods are studied and proposed. Firstly the X-ray pulsar measuring signal model is studied, and verify the model by the RXTE data. The relationship between observation time and the SNR of folded outline has been studied. Secondly the methods of reducing the pulsar signal noise based on wavelet transform are studied, and verify the validity of method. This paper also makes analysis of the influence of disappear moment order number and the decomposition layers on the noise reduction effect. Based on studying the phase estimation traditional methods, the multi-scale folding processing method and weighted phase estimation method are proposed. By comparing with traditional methods the simulation results verify the feasibility of multi-scale processing method of folding, and the weighted phase estimation has better robustness. Finally the pulsar signal cycle detection method based on optimal matching principle is proposed under the situation of the lack speed information. And verify its effectiveness through simulation.The methods of integer ambiguity resolution of X-ray pulsar navigation has been studied and proposed in this thesis. Firstly this paper studies the background of the integer ambiguity problem in X-ray pulsar navigation. Through studying the algorithms of integer ambiguity resolution in GPS navigation, make conclusion that the methods based on ambiguity function and LAMBDA are difficult to be applied to the XNAV. This thesis proposes an algorithm based on searching in ambiguity domain, which using only three base search stars. The method of base stars selection and specific processes of the proposed has been discussed and proposed. Finally making analyses of the relationship between accuracy of integer ambiguity resolution and the different influencing factors, and make comparison between algorithms proposed with the traditional algorithms by mathematical simulation.The application of X-ray pulsar navigation in Mars orbiter has been studied. Firstly the orbit dynamics model of orbiter is introduced. The visibility of X-ray pulsar is studied, and the influence factors are analyzed. This part also design the navigation filters based on EKF, including the punctual and positioning navigation filters and attitude integrated navigation filter. The navigation method of Single detector for multi-star observation is studied, and also compared with the method of multi-detector for multi-star. Finally the influence of the pulsar direction error and observation error on navigation has been studied.