Research On The Low Speed Performance Of The Servo System Of Coude-Type Laser Tracking And Aiming Turntable

Point,acquisition and tracking(PAT)of the target beam quickly,stably and accurately by the photoelectric tracking and pointing turntable is an important prerequisite for the construction of space laser communication chain.The inter satellite laser system has the characteristics of long communication link and small divergence angle of laser beam,and the communication terminals are slow-moving systems.Its low-speed performance is affected by friction interference It is difficult to maintain the stable link because of the influence of motor torque fluctuation and quantization link.This paper takes the light and miniaturized Coude type laser communication tracking and pointing turntable as the research object,mainly from the influence of friction interference,explores its influence on the low-speed performance,and improves the low-speed performance of the tracking and pointing turntable servo system,so as to realize the turntable’s stable and accurate tracking of the slowly changing target beam,and improve the Los accuracy,which is of great value to the laser communication system.According to the performance requirements of the tracking and pointing turntable,the development scheme of the turntable servo system is formulated.The main components of the servo system,such as executive motor,feedback grating encoder and image detector,are selected.The Coude optical system is modeled and analyzed,and the detector angle measurement and tracking model is deduced.According to the performance design requirements of the tracking and aiming turntable,the development scheme of the turntable servo system is formulated.The main components of the servo system,such as the execution motor,vibration mirror,feedback raster encoder and image detector,are selected,and the Coude optical path system is modeled,and the angle measuring and tracking model of the detector is deduced.Simulate or analyze the friction interference,quantification link influence and fluctuating moment that affect the low-speed performance,and give the evaluation index of the low-speed performance.For the deterioration of low-speed performance of turntable near zero speed caused by friction interference,the friction model feed-forward compensation is used to improve the performance.In order to obtain accurate Stribeckfriction model,differential evolution algorithm is used for curve fitting identification.Aiming at the error of model identification and the influence of other disturbance factors on the system,a fuzzy adaptive PID is introduced in the position ring,and the P,I,D parameters are adjusted online by the fuzzy rule base.The simulation verifies that the friction model feed-forward and the fuzzy adaptive PID algorithm can improve the low-speed performance well.The hardware design of the servo control system of the tracking and aiming turntable and the control strategy design of the three closed-loop motor and the closed-loop image tracking based on the angle measuring model are carried out.An experimental platform is built to test the tracking accuracy of Coude-type tracking and sighting platform is better than 16.12μrad after friction compensation under external disturbance of 0.16 Hz amplitude0.1°,which meets the design requirements.At the same time,the angle measurement model is verified to improve the low-speed capture performance through in-field capture experiments.