Application of variable structure control in PAT system for space optical communication

A variable structure controller is designed for Pointing,Acquisition and Tracking(PAT) system in space optical communication based on discrete exponent reaching law and discrete model for the controlled plant.By changing parameters related to the reaching law,the chattering phenomenon of system is eliminated so that the system converges to the equilibrium in sliding mode and much higher tracking accuracy is achieved in tracking dynamic target than that of conventional frequency domain method.Simulation results show that:compared with conventional frequency domain method for the pointing and tracking performance,two order of magnitude improvement is obtained in dynamic target tracking accuracy with variable structure controller.The feasibility of the design method is also proved.