Beaconless Acquisition And Tracking Technologies For Space Laser Communication System

As the LEO satellite launch carrying with light,low power and small volume communication load,and satellite network to realize globalization coverage which takes the growing demand of communication technology,space laser communication with signal beam scanning and coverage of uncertainty cone,and beaconless acquisition technology as a new representative strategy arises at the historic moment,the analysis for the main influence factors of communication terminal control accuracy and tracking performance is important,and also the design of control strategy is the key to establish a high-speed data communication link.High acquisition probability and stable tracking accuracy are important guarantee for reliable inter satellite laser communication.However,due to the relative motion between communication terminals,the vibration of satellite platform and the small divergence angle of system signal beam,it is more difficult to acquire without beacon.Therefore,starting from the scanning strategy,compensation algorithm and tracking control strategy of beaconless acquisition and tracking,this paper has carried out in-depth theoretical research,key technology research and experimental verification on the beaconless acquisition and tracking servo system of space laser communication system.Firstly,the paper makes a deep study for the mechanism and working principle of beaconless acquisition.In order to solve the problem that the existing beaconless scanning mode can not cover a large range of uncertain areas,we propose a new scanning mode of combined operation of turntable and galvanometer.On this basis,the scanning model is established,verified by simulation and optimized design of each parameter.Aiming at the problem that the small beam divergence angle will reduce the acquisition probability of the system,using Gaussian white noise filtering method to simulate platform vibration.This method can analyze the leakage caused by vibration,so as to select the appropriate overlap factor,more effectively compensate the leakage in the acquisition process,and improve the acquisition probability of the system.Secondly,based on communication terminal system of beaconless acquisition analyzes the causes and characteristics of coordinate coupling and the effects on the optical closed-loop tracking control system.The optical transfer relationship between the plane mirror and the tracking camera in the periscopic scanning structure is studied and the beamtransmission matrix model of the communication terminal is established.The factors that affect the stability of optical path pointing are given,a decoupling model is established based on a two-dimensional servo turntable.The reliability of the model is verified by simulation and test system test.The relative position changing between the plane mirror and the tracking camera is solved,and the coordinate decoupling of the rough aiming mechanism is realized to weaken the influence of structural factors on the system's coarse and fine compound tracking precision.Thirdly,this paper aims to design advanced control algorithm to enhance the anti-interference ability of the system,and improve the dynamic response performance of the system and the stability of low speed.This paper analyzes the main factors that affect the performance of the servo system,including the dead zone effect of the inverter and the detection error of the output phase current of the motor.In order to realize the high precision stable tracking under the disturbance condition,the influence of periodic torque fluctuation on tracking precision of control system is studied.Adaptive sliding mode iterative learning algorithm is designed based on the new reaching law,and the speed loop is corrected by the controlling output value for dive at the spindle servo system of communication terminal,which improves the speed stability and the dynamic response performance of the terminal servo system for the composite tracking process,at the same time the torque ripple is effectively suppressed and the robustness of the system is enhanced.Finally,Indoor and outdoor experiment are carried out to verify the performance of the beaconless acquisition and tracking system.The tracking accuracy is better than 2?rad in indoor single terminal dynamic tracking experiment,and verify the accuracy of the decoupling model and single terminal stable tracking.Through the experiment of 4.62 km laser communication,the feasibility of the rectangular spiral scanning with the combination of galvanometer and turntable is verified in the acquisition stage,and the acquisition time is better than 49.1s.In the tracking phase,the relative motion of the satellite is simulated by a six degree of freedom turntable.Under this disturbance condition,the system's coarse fine composite tracking accuracy is better than 6?rad.The research work of this paper provides a reference for the optimization design of space laser communication beaconless acquisition and tracking system,and has certain significance for the future development of light and small laser communication system,space networking and the construction of integrated information network.