Design And Simulation Of Control Algorithm For Laser Beam Pointing In Intersatellite Optical Communication

Inter-satellite laser communication will lead the development direction in the optical communication field, based on its advantage of wide bandwidth, high security, compress volume, light weight and low consumption. In the Inter-satellite laser communication system, because the laser beam is very narrow and the transmission distance is too far, PAT (Pointing Acquisition and Tracking) is the key technology to establish and maintain the optical communication link. In the PAT system, close-loop control algorithm for the two-dimension rotate platforms motors is one of the key technologies which have to be solved.Because of the changeability and unpredictability of the outer-space, the models of two-dimension rotate platforms motors will be effected, so that the models will become time-varied and nonlinearized. In order to solve the impact of the unpredictable facts for the pointing system, NN (nerval network) PID control algorithm (self-adjustable control algorithm) is presented. The NN PID is the effective control algorithm to solve the time-varied and nonlinearized models of the two-dimension rotate platforms motors by simulation experiments.Based on the background of the research on the inter-satellite laser communication system, design and simulation of the laser beam pointing control algorithm have been done. The property of the laser beam pointing system of inter-satellite laser communication is analyzed. The control strategy of the laser beam pointing system of inter-satellite laser communication is obtained. Present the process of designing the system-identification of the laser beam pointing system of inter-satellite laser communication. Design the identification algorithm based on the BP NN model. The methods of designing the controller of the laser beam pointing system of inter-satellite laser communication is introduced, including the regular digital PID controller and NN PID controller. The simulation experiments of control algorithm of the laser beam pointing system of inter-satellite laser communication is conducted. Linear-time-unvaried model, linear-time-varied model and nonlinear-time-varied model are involved respectively in the experiments by NN PID controller. Frequency response and control precision are both satisfied by the engineering requirement. The innovation of this paper are as follows: the NN PID controller is presented in the laser beam pointing system of inter-satellite laser communication to solve the problems of time-varied model and nonlinearized model seduced by the unpredictable facts of the outer-space; establish the Linear-time-unvaried model, linear-time-varied model and nonlinear-time-varied model of the laser beam pointing system of inter-satellite laser communication and conduct the simulation experiment to prove the validity and feasibility of the NN PID controller. All in all, NN PID control algorithm is very meaningful refer to the inter-satellite laser communication.Finally, based on the simulation experiments, improved algorithm of control and constructive idea are presented.