Research On Key Tracking Technologies Of Vehicle-Borne LEO Satellite Survey Station

With the development and application of space technology,many countries have built space target surveillance networks.Vehicle-borne photoelectric survey stations,which can deployed flexibly,are effective supplements to the ground-based surveillance network.Based on the research of vehicle-borne LEO satellite survey station,this paper mainly studies the key tracking technologies of vehicle-borne photoelectric tracking equipment.In this paper,an accurate transfer function model of turntable is obtained by using the improved differential evolution algorithm.Taking the minimum angular velocity deviation of the triaxial turntable as the index,a minimum deviation of triaxial velocity control method is designed.A static pointing correction method for triaxial turntable based on measurement equation is proposed.Finally,this paper constructs a servo control system of triaxial tracking turntable,and verifies the researches above.The main work of this paper includes:1.The composition of vehicle-borne LEO satellite survey station is summarized,and the operating principle is briefly described by introducing its workflow.Based on analysis,it is pointed out that the tracking accuracy of the tracking turntable and the pointing accuracy of the tracking turntable determine the performance of the survey station.The transfer function identification method,the control method of the triaxial tracking turntable and the static pointing correction method of the triaxial tracking turntable are also analyzed.2.By strengthening the randomness of search and updating the parameters of the algorithm online,an improved differential evolution algorithm is proposed.The benchmark functions are used to test the performances of improved differential evolution algorithm and other heuristic algorithms,which prove that the algorithm has faster convergence speed and stronger global optimization ability.Furthermore,the improved differential evolution algorithm is used to identify the system of an experimental turntable,and the transfer function parameter model which accurately reflects the actual system is obtained.3.The pointing models of alt-azimuth and alt-alt tracking turntable are deduced,and the causes and effects of tracking "blind zone" problem are analyzed.The motion model of the triaxial tracking turntable is studied.It is pointed out that the triaxial turntable can't divide the pointing deviation into three axes.In order to make full use of the characteristics of the triaxial tracking turntable,a control method based on the minimum of the triaxial angular velocity deviation is proposed.The improved differential evolution algorithm and a Moor-Penrose generalized inverse matrix algorithm are used to realize the control method.The alt-azimuth method,alt-alt method,and the minimum deviation of triaxial velocity control method are compared through simulation experiments.The results prove that the minimum deviation of triaxial velocity control method can effectively solve the tracking "blind zone" problem in the two-axis control method,and reduce the requirements for the structural stiffness,motor torques and servo control bandwidth of the tracking turntable,by distributing the pointing deviation evenly to each shafting.4.The error sources in the measurement of triaxial tracking turntable are analyzed.The timing error,positioning error and orientation error of vehicle-borne LEO satellite survey station are taken into account in azimuth axis tilt and azimuth axis zero position error,which reduces the number of error sources.A static pointing correction method of triaxial tracking turntable based on spherical harmonic function is designed.By deducing the measurement equation of the triaxial turntable,a static pointing correction method based on the measurement equation is proposed.The two methods are validated and compared experimentally.It is considered that the triaxial turntable pointing correction method based on measurement equation is more suitable for vehicle-borne LEO satellite survey station.5.Taking the azimuth shaft as an example,the improved differential evolution algorithm is used to identify the transfer function.The identification results can accurately describe the true system and provide a basis for the servo controller design.The minimum deviation of triaxial velocity control method is used in the servo controller to calculate in real-time.Rotating target and overhead target are used to guide the triaxial turntable respectively.Compared by the horizontal method,the tracking accuracy is improved.Aiming at the practical application of vehicle-borne LEO satellite survey station,a simplified static pointing correction algorithm based on measurement equation is proposed,which only calculates the azimuth axis tilt and azimuth zero position error,so as to shorten the time of calculating pointing correction parameters after the deployment of vehicle-borne LEO satellite survey station.