Research On TTM And DM Optimal Control Technology In Horizontal Atmospheric Adaptive System

In recent years,the communication bandwidth and rate required for horizontal atmospheric laser communication have been increasing rapidly,and the control accuracy of the communication system will also be reduced due to atmospheric turbulence changing the beam transmission characteristics.Usually,adaptive optics is used to correct the interference of atmospheric turbulence in real time.In the adaptive optics system,the tip-tilt mirror corrects the first-order overall tilt,and the deformable mirror corrects the high-order wavefront distortion.In addition,the working environment of the adaptive optics system and the system platform itself will also introduce non-turbulent aberration disturbances to the system,mainly including narrow-band disturbances generated by air conditioners or coolers.In addition to disturbances caused by atmospheric turbulence,these non-turbulent aberration disturbances degrade the performance of the system.In this regard,this paper designs a horizontal laser communication adaptive optics system for the correction of turbulent disturbances and non-turbulent aberration disturbances.Correction experiments are carried out indoors and outdoors,and a series of results are obtained:Firstly,in order to solve the problem of poor control accuracy in adaptive optics in the presence of narrow-band disturbances,a sliding-mode control method based on disturbance observer is proposed to suppress structural vibration.In the control system,a new disturbance observer is added to the traditional sliding mode control method,and chattering is suppressed by designing a new sliding mode control rate.Secondly,Through the numerical simulation results of the sliding mode control based on the disturbance observer,it is shown that the controller can track the performance of the system well and realize the optimal control in the presence or absence of narrowband disturbances.Build a horizontal adaptive optics system,adjust the optical path of the system,determine the indicators of key components,and conduct indoor and outdoor experiments.Finally,The atmospheric adaptive correction experiment is carried out between buildings with a horizontal distance of about 1km,and the root mean square(RMS)before and after adaptive optics correction is compared and analyzed.Before the closed-loop correction of the system,the root mean square error of the tip-tilt mirror azimuth axis is1.64 μrad,the root mean square error of the pitch axis is 1.97 μrad,and the wavefront distortion RMS value is 0.19-0.4λ.After adaptive optics closed-loop correction,the root mean square error of the tip-tilt mirror azimuth axis is 1.08 μrad,and the root mean square error of the pitch axis is 1.61 μrad.The wavefront distortion RMS value is 0.11-0.2 l.At the same time,the RMS aberration of 15 hours a day is tested and recorded.The method proposed in this paper improves the system performance to a certain extent in the system application.