Experimental Research On Airborne Non-coaxial Laser Communication Alignment System

Airborne laser communication systems are susceptible to atmospheric turbulence and airborne platform vibrations,which can reduce the tracking accuracy and line of sight alignment accuracy of acquisition,pointing and tracking(APT)systems.In order to achieve real-time alignment between the ground end and the airborne end,this paper designs an APT system applied to unmanned aerial vehicle platforms.Among them,the ground transmitting end uses a camera and a pan tilt to track the image of the drone,while the airborne end uses a two-dimensional reflector to control the beam and achieve non confocal axis alignment between the transmitting and receiving sides.The main research content is as follows:1.A ground-side alignment method using a camera and gimbal for image tracking is designed.The particle filter algorithm of multi-feature fusion is used as the tracking algorithm to realize the image tracking of the UAV,and the two-dimensional aiming platform is used to embed the piezoelectric micro-motion platform as the actuator to control the pointing of the emitted beam for alignment,and the dynamic response of the system is analyzed.The control interface of the upper computer is designed to realize the visual operation of the ground end alignment system.2.For the alignment requirements of airborne laser communication,a two-dimensional mirror with a large dynamic adjustment range is used as the control core of the airborne end alignment system.The position and speed double closed-loop method is used to control the twodimensional mirror to achieve beam alignment,and the dynamic response of the system is analyzed.The through-hole four-quadrant detector is used as the position detection device to design the spot position detection system,and the two-dimensional Gaussian distribution spot detection algorithm is used.Through simulation analysis,it is found that the algorithm can effectively reduce the relative error of spot position detection.3.According to the alignment method proposed in this paper,the alignment performance of the ground end and the airborne end are tested experimentally.Finally,the fine alignment system is mounted on the six-rotor UAV,and the ground-side coarse alignment system is combined to build an airborne laser communication link and conduct experiments to verify the feasibility of the method in this paper applied to the airborne laser communication system.The experimental results show that the tracking accuracy of the system is 13.98 μrad,the electrical signal amplitude output by the signal detector is 23.0 mV,and the maximum relative error of the spot position detection system is 0.97%,which is 36.6%higher than the traditional detection method.Using the alignment method in this paper,the alignment can be completed without data return,and the downlink can also be established while quickly establishing the uplink,without the need for a stable platform in the air.