Research On X-ray Pulsar Navigation Signal Processing Method

X-ray pulsar navigation is an emerging autonomous navigation technology,it utilizes the X-ray pulsar emits as the navigation signal source,which does not rely on the ground monitoring equipment or space-based navigation satellite,it is especially suitable for autonomous navigation in deep space exploration missions.In this paper,the X-ray pulsar autonomous navigation method is the main application background.Considering the factors affecting the pulsar navigation accuracy such as pulsar signal noise,emphasis error,abnormal measurement,the research is developed in pulsar selection,signal processing,navigation algorithm.The main research contents are listed as follows:The pulsar selection optimization method for X-ray pulsar autonomous navigation is studied.According to the characteristics of X-ray pulsar,the European Pulsar Network is selected as the database.Then,more than 1000 pulsars' data collected in the European Pulsar Network database were analyzed for navigation.Considering the factors which affect the visibility such as celestial block and solar strong radiation,the X-ray pulsar in navigation database are processed with the primary selection.On this basis,the Pulsar observation model precision factor for pulsar selection method is proposed to reduce the estimation error of the navigation filtering algorithm.The observed signal denoising and recognition method for pulsar navigation system is studied.A signal denoising method based on empirical mode decomposition is proposed aiming at the problem that the noise exists in the observation signal can effect the calculation accuracy of the observation of navigation system.The noise level estimation method is designed based on the local region correlation analysis.Then,the adaptive threshold is designed based on the noise standard deviation.Finally,the designed adaptive threshold is utilized in the proposed EMD based signal denoising method in order to improve the signal to noise ratio.In the aspect of signal recognition,the signal recognition algorithm is designed based on the instantaneous amplitude characteristics of radiation intensity in X-ray pulsar signal's time domain in order to improve the velocity of X-ray pulsar observation signal.The emphasis error correction method for X-ray pulsar navigation system is studied.Based on the analysis of navigation measurement bias caused by the emphasis error,a robust Kalman filter based on matrix inequality is proposed with the established measurement model which contains the emphasis error.During the filtering process,measurement residual and matrix inequality is utilized to calculate the lower bound of covariance of emphasis error and further revise the filter gain.Then,the final state estimation value is obtained.The proposed robust Kalman filer can effectivelydecrease the influence of emphasis error to the pulsar navigation system.The abnormal measurement correction method for X-ray pulsar navigation system is studied.Considering the dramatic changes of measurement residual of unscented Kalman filter in presents of abnormal measurement,an adaptive unscented Kalman filter is proposed with the designed abnormal detection function based on the in statistics measurement residual.The adaptive tuning matrix is designed based on the covariance of measurement residual to revise the filter gain.The adaptive unscented Kalman filter can effectively decrease the influence of abnormal measurement to pulsar navigation system.