The Research Of Iterative Algorithm And Its Optimal Parameters For Pulsar Time Delay Estimation

Pulsar is a neutron star with high speed rotation,stable period and the ability to radiate X-ray photons.Among them,the most remarkable characteristic is that the signal period has excellent stability.This feature makes the pulsar in near earth orbit,geostationary orbit,elliptical orbit,orbit and interplanetary space navigation and deep space navigation of spacecraft with position,speed and time rich navigation information.Therefore,X-ray pulsar navigation is of great strategic significance and great potential for development.In pulsar navigation,the pulse arrival time is the basic observation of the spacecraft and the position of the pulsars,and the accuracy of the arrival time estimation directly affects the positioning performance.Since the pulse arrival time estimation accuracy is determined by the time delay estimation accuracy,The delay estimate becomes a key factor in determining the accuracy of pulsar navigation positioning.In order to further improve the accuracy and efficiency of the pulse delay estimation algorithm,the paper studies the pulse delay in pulsar navigation,and the main research contents are as follows:1.In order to solve the contradiction between real time and accuracy in iterative operation in Taylor FFT,a new algorithm based on variable step size iteration is proposed.First,the standard pulse profile and the cumulative pulse profile are processed by one dimension slice,then,the least square fitting method is used to estimate the gap function.Finally,the minimum value of the gap function is calculated by the variable step size iteration technique.Through the classification of the iterative process,the number of iterations can be reduced effectively,and the time delay estimation can be realized efficiently and accurately,which can effectively reduce the CPU load.In addition,the proposed algorithm is compared with several existing algorithms,,including the Taylor FFT,cross-correlation method and firefly optimization algorithm.The pulsar time delay estimation method based on the EPN pulsar simulation signal is simulated and verified.2.Aiming at the contradiction between the amount of computation and the estimation precision in the iterative algorithm,we explored the effects of the i nitial iterative step and the iterative parameters on the accuracy of the propose d algorithm and the amount of computation.Firstly,we introduced the advantages and disadvantages of different iterative methods,and then the convergence of the pulse delay estimation algorithm based on variable step iteration is analyze d.Next,we studied the effects of the initial steps and the iterative parameters o n the accuracy and real-time of the delay estimation.In order to improve the p ulse delay estimation accuracy and real-time,the simulation results and numerica 1 analysis are carried out to determine the optimal initial step size and the opt imal iteration parameters in the algorithm.In this paper,the pulsar signal is obtained by the Europe Pulsar Network database(EPN),which is disclosed by the European Space Agency,and the pulsar cumulative pulse profile is generated by simulation.Then,the accuracy and computation time of the pulse delay estimation algorithm based on the variable step iteration are simulated by using the simulation platform Matlab.Experiments show that the pulsar time delay estimation algorithm based on variable step iteration is a fast delay estimation algorithm for pulsar short time observation.