Design And Fault Diagnosis Of The Coarse Pointing Control System In Satellite Laser Communication

Intersatellite laser communication can be considered as the consequent development of satellite communication technology, and the narrow laser beam and long communication distance cause the difficulty of establishing and keeping the link in complex space environment. So it is necessary to design a PAT (Pointing, Acquisition and Tracking) system to prevent the signal loss due to link failure in satellite laser communication system. The PAT technology is pivotal to establishing and keeping the laser communication link. In the background of the subject"Relay Satellite Link Technology"taken on by School of Astronautics (HIT), this paper researches and designs the coarse pointing control system of PAT system.Firstly, this paper summarizes the background and significance of research on satellite laser communication, then analyses and compares the current status and progress of this technology at home and abroad. In addition, the importance and working principle of PAT system are expounded in detail, and its general design structure is given.Secondly, this paper provides a comprehensive introduction to each function unit of coarse pointing control system, then proposes the system's control scheme which includes selecting the PID control algorithm with integral separation and output limit, solving the mathematical model of controlled object by frequency response method and designing the speed loop (position loop) according to Typeâ… (â…¡) System model. On this basis, the relevant simulation experiments of coarse pointing control system are done, and meanwhile the response curves are given. In addition, the software and hardware design of controller unit is described alone in detail, and the better control effect is obtained because the parameter tuning of whole system is performed by trial and error method.Finally, this paper makes a research on the fault diagnosis of coarse pointing control system by fault tree analysis. The fault tree is constructed considering the abnormal running of motor as top event, and its qualitative and quantitative analysis is performed by mathematical method. The application shows that the fault tree analysis used in the fault diagnosis of coarse pointing control system is feasible.