| Compared with the traditional microwave communication,Satellite laser communication has the advantages of high communication rate,strong anti-interference energy and less resource consumption which is a new communication technology.As an important part of space high-speed information network,intersatellite laser communication plays an important role in data relay.It need special acquisition pointing and tracking beam control system(APT)to realize communication in thousands of kilometers by using magnitude of micro radians beam.The main problems existing in APT system at present are big weight,large volume and poor pointing accuracy,based on actual engineering requirements,a combination of numerical simulation and experimental analysis method is used in beam pointing and structure study of the APT system and the main content are as follows:Firstly,the factors affecting the pointing indicators of APT beam control system are analyzed.The influence of angle random error on pointing accuracy of capturing mechanism(CM)of APT is analyzed,The forming process of angle random error is studied,an improved Rayleigh angle random error model is proposed.Compared with traditional Rayleigh model,the prediction accuracy of link maintain time can rise 2.8 times by the new model;The relative motion between satellites is analyzed and the model is established,the calculation formulas of intersatellite distance,angle,velocity are derived,and the simulation has done based on actual satellites data,the simulation results shown that the intersatellite angle speed of LEO-LEO link is the biggest wich is 0.5°/s;The pointing error analysis basic theory of relay optical path is established,the error transfer formulations are given,and the generating principle of coaxiality error is analyzed.The second,aimed at the problems of large volume,big weight and poor pointing accuracy,take engineering requirements into consideration,the L-type APT is studied deeply.Through comparison of different APT performance,the L-type APT is determined as the research object,The capture mechanism of L-type APT is optimized,the internal relay optical path is studied,the pointing error of axis is analyzed,the virtual prototype is established and the system mode is analyzed.Then,the calculation method of pointing accuracy of relay optical path is proposed,the error source is analyzed and the influence of relay error sources on beam pointing is deduced,then the pointing error calculation model of communication receive path,communication transmit path,beacon transmit path,coarse tracking path and fine tracking path are established based on coordinate transformation method and the pointing error distribution regular acquired which can provide basis for the follow-up experiments.Soon after,based on the previous optimized design,L-type APT system performance testing platform is built,the coaxiality and pointing accuracy are tested,the experimental results shown that the first-order natural frequency of the system is 149 Hz the coaxiality is 0.3?rad and the pointing accuracy of the capturing mechanism is 29.9?rad,the experimental results accord with simulation results and meet the design requirements.At last,for small satellite platform,a three-point supported flexible APT institution is proposed.The institution is parallel connected by flexible beam,flexible rod and flexible hinge.The configuration process is derived,the main flexible parts are optimizaition designed and the relationship between structural parameter and pointing angle,system stability is analyzed,the pointing accuracy of flexible APT capture mechanism is analyzed in virtual prototype and 3?rad can be achieved which is higher than mechanical shaft.The research contents indicate the study direction for new APT mechanism design,reduce its weight,volume and improve the pointing accuracy.The research content in this paper provides some reference value for improving APT system performance in practical engineering applications. |
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