Research On Spot Tracking System In APT System Of Wireless Laser Communication

Wireless laser communication technology is a communication technology with strong anti-jamming and large communication capacity.It is a very advanced and key technology in the field of communication.However,due to atmospheric turbulence,mechanical jitter and many other factors,the wireless laser communication link is greatly disturbed,and even the communication link will be interrupted..a capturing,pointing,and tracking(Acquisition,Tracking and Pointing,APT)system isneeded to establish a communication link and guarantee ong-term stability and effectiveness of links.Fine tracking system is the core of APT system.Itdetermines the performance of the whole system.Therefore,a precise tracking system with high accuracy and stability is very important.The main work accomplished in this thesis is:(1)On the design of Digital Controller,the system combines the characteristics of the system and the external environment with the improved PI algorithm as the digital controller of the system.The GPRS module is introduced into the precise tracking process as the unit of the closed-loop control error signal feedback.The GPRS module is an auxiliary communication module of the system,and the information communication between the two terminal GPRS devices is communicated.The GPRS module can quickly understand the current state of communication double ends and achieve the tracking of beacon spot.(2)The control software of the tracking system is designed.The functions of the software include the control of servo motor,the acquisition and display of far-field spot image,and the tracking of spot signal.The system was preprocessed,the edge extraction of the image,the standard circle fitting and the filling of the map line area.Finally,a standard circular spot gray scale was obtained as a standard.The target spot of the error signal is extracted.The experimental platform is set up.The beacon is emitted by the transmitter and collected by the CCD camera at the receiver.There are two computers in the control unit,and they can processes the spot image and controls the servo motor.The GPRS module of the auxiliary unit gives feedback to the error signal.Finally,the field tracking experiment of 5.2km is completed.The tracking accuracy is up to 5.4 ?rad,which verifies the reliability of the system.