Research On Control Method Of Coarse Pointing In Laser Intersatellite Communication

Laser inter-satellite communication is one of free space laser communications, and is the foundation of the future heaven and earth integration communication network. In order to successfully established a communication link, terminal antenna usually adopts compound axis control method, i.e. coarse aiming system and fine aiming system coordinately control. This paper mainly research object is coarse aiming system, in order to achieve rough aiming system of high precision and strong robustness position servo, overcome interference and parameter perturbation, design the variable structure controller based on neural network. And design software and hardware of coarse aim control unit.Firstly, this paper introduces acquisition, pointing and tracking process in Laser inter-satellite communication, analyses the composition of coarse aiming system. Brushless dc motor is controlled object of coarse aiming system, establishing the mathematical model of brushless dc motor, analyzing influences on system of parameter perturbation in the space environment and interference. Focuses on the analysis of the temperature changes in resistance to change and friction on the influence of high accuracy servo system. The temperature change caused resistance changes and the influences of friction in high accuracy servo system are emphatically analyzed.Secondly, in order to guarantee the system control precision and robust stability, design sliding mode variable structure controller, and compare simulation diagram with PD control. Using saturation function replaces sign function to reduce buffeting phenomenon.In order to reduce the time of reaching mode step, improve the position tracking precision, apply integral sliding surface. Using an adaptive algorithm and RBF neural network estimated upper bound joint of parameter change and interference, making use of estimated value design integral sliding mode controller. Using Lyapunov method analyse the stability of system. In order to further reduce the buffeting in sliding mode control, the RBF neural network variable structure controller was designed, the switch function as RBF neural network's input, variable structure controller as the output. Because controller by continuous gaussian function replaced the discontinuous switch control, so system eliminate buffeting.Finally, design hardware circuit and software realization of coarse aim control unit. The main function of coarse aim control unit is establishment stable and reliable communications between subject control unit and coarse aiming drive control unit.