Research On Acquisition And Tracking Technology Of Airborne Laser Communication

Free space laser communication is one of the most potential and importantcommunication model in high-rate wide-frequency information transmittance, with massivedata volume, anti-disturbance, anti-acquisition,mini volume, lightweight, low powerdissipation and so on. APT system（Acquisition，Pointing，Tracking，called by APT）, as afundamental factor, is firstly necessary for laser communication. The key technology of APTsystem is thoroughly researched based on airborne laser communication.Tracking precision and beam angle of airborne laser communication is designed, withtaking the analysis of the influence of communication constraint conditions related to APT.The paper takes atmosphere channel, background rays and load movement trait as main outerfactors of APT. Based on these influences, the relation of tracking precision and beam angleis discussed in the error possibility distribution of received light energy and communicationsymbol error ratio. After parameter optimization, the final tracking angle and beam angle isobtained, tracking angle is20μrad (maximum-maximum number), beam angle is180μrad.APT high rate acquisition technology is researched, scanning way, scanning trail andcompensation calculation are confirmed, a fully optical acquisition method, achieving noelectronic auxiliary high rate acquisition, is discussed. GPS/INS is used to high rate andprecision initiate pointing. Airborne laser communication initial acquisition undefined regionarea is figured out through the analysis of factors influencingacquisition. The advantage anddisadvantage of scanning way and trail in laser communication seem to be discussed,scanning and acquisition scheme is adopted on the basis of airborne laser communication:missing scanning and spiral scanning.Gyro compensationinertia scanning can be the solutionof miss scanning, the scan effect is proved in the experiment; the rectangle beacon fullyoptical acquisition is put forward in order to avoid the dependence on the electronic auxiliaryway, calculating acquisition time and possibility, optimizing beacon shape, short distanceprinciple experiment is finished. The technological support is provided in electrical magneticinterruption environment.As for greatly precise tracking of airborne laser communication, two-axis and four framedynamics and kinematics model is built up, turntable structure and servo system design arefinished, while precise tracking system is shortly illustrated. Wide range movement and highprecision tracking can be achieved by coarse-and-precise compound structure, due to the fastpose vary and drastic vibration airplane platform. Coarse tracking turntable structure isexcellent anti-interruption two-axis and four frame, installing vibration reduction equipmentbetween inner and outer frame to reduce high frequency disturbance to inner frame,vibrationreduction coupling caused by main servo and passive vibration reduction, raising inner loopprecision. The simulation of dynamics, kinematics and isolating vibration effect prove thattwo-axis and four frame turntables be the solution of high precise tracking. Coarse trackingturntable structure design is finished by the above analysis and the main components and overall of turntable is taken into finite element method; meanwhile the mechanical scanfrequency is completed and show that the design can satisfied with stiffness requirement.Fine-tracking system design and two high precision tracking technologies (micro arc anglecalculation and high precision actuator) are discussed; fine-tracking system design result hasbeen formed.The measurementmethod of tracking and stability precision of airborneturntable isilluminated. The first domestic airborne-airborne laser communication experiment iscompleted. For themeasurement way of turntable tracking and stability precision, anequipment of long focus distance parallel optical pipe and high collection frequency figuresensor is introduced, in which high precise optical blot can be tested. The precision issuperior to1.5μrad and then coarse tracking turntable tracking and stability precision in theroom is finished.In the end, the functions of APT system in laser communication can bedefined by the first domestic airborne-airborne laser communication experiment. As a result,the acquisition possibility is96.7%,the average acquisition time is18.3s,coarse trackingmaximum error: bearing axis±60μrad， pitch axis±40μrad，fine tracking maximum error:Bearing axis±15μrad，pitch axis±10μrad. The results are satisfied with communicationdemand.The APT scheme of rotating parabolic multi-reflection joint is raised by onepoint-multipoint laser communication demand, the mechanical structure that is made up of6mirror combination design is finished and scanning\tracking model is built up adoptingdynamic optical principle, each mirror can finish bearing60°, pitch±15target scanning andtracking. The simulation prove that the APT system carry out multi-target high rateacquisition and precision tracking of bearing360°, pitch±15°acquisition and tracking.