Simulation Of APT System For Airborne Laser Communication

The technology of bidirectional and direct transmission of image,language and data-related information through laser beams in space is free-space optical communication.Because of its small light beam divergence and good directivity,it has the advantages of high data transmission rate,strong protocol transparency,high security and confidentiality,fast network construction speed and strong anti-interference ability.It is one of the hottest communications development in the future.APT(Acquisition,Pointing,Tracking)related technologies exist as important and difficult points in the realization of airborne laser communication.This article is based on airborne laser communication and further explores the core technologies in the APT system.The main work is as follows:1.The basic composition of the wireless optical communication system is introduced,and the composition,working process and working principle of the APT sub-system are analyzed in detail,and the main parameters and performance indicators of the APT system are given.2.Based on the real-time updated position and attitude information of the aircraft,the GPS/INS system is used to analyze the source of error,and the coordinate conversion theory is used to calculate the boresight angle to realize the initial pointing and rapid capture of the airborne laser communication system.3.In order to capture,track and aim the airborne laser communication signal with higher accuracy,the coarse and fine two-stage compound axis control technology is adopted in the process of establishing the tracking system.The coarse tracking servo system completes fast pointing and fast capturing.By adding current loop,speed loop and position loop,its mathematical models are established and simulated;Fine adjustment of fine tracking servo system realizes accurate aiming and fine tracking.By introducing fast steering mirror(FSM)and four quadrant detector(QD)and other correction links,the Bode diagram,Nicols diagram and Nyquist diagram are drawn,and the stability and performance of the system are simulated and analyzed.The results show that the current loop,velocity loop and position loop make the system obtain higher stability and better dynamic performance,and ensure the tracking accuracy within 180 μrad in the coarse tracking stage and 15 μrad in the fine tracking stage.