Research On LQG Wavefront Control Technology In Adaptive Optical System

In laser communication,due to the influence factors such as atmospheric turbulence and measurement noise,the beam will produce serious distortion in the transmission process,resulting in a significant reduction in optical communication quality.The introduction of Adaptive Optics(AO)technology effectively compensates the wavefront aberration of the received beam signal and improves the communication quality.The AO system is composed of software and hardware,and the control algorithm is the core of the software.The performance of the AO system directly determines the correction effect of the wavefront distortion.Therefore,it is of great significance to study the wavefront control technology of AO system.This paper studies the application principle and calibration effect of Linear Quadratic Gaussian(LQG)control algorithm in AO system,and compares it with Proportional Integral(PI)control algorithm.The main work is as follows:1.The basic structure of the traditional AO system is briefly introduced,the working principle of the system is elaborated,and the function and characteristics of the core components are elaborated,and the main factors affecting the quality of wireless optical signal transmission are also introduced,such as atmospheric turbulence disturbance,Shack-Hartmann(H-S)wavefront sensor measurement noise and other noise,etc.The expressions of the evaluation objective functions of the wave front peak-valley value,the wave front root-mean-square value and the wave front power spectral density are derived,and the phase plate generated by atmospheric turbulence disturbance is simulated by Zernike polynomial.2.In this paper,the minimized residual wave front after correction is used as the performance index of the LQG control algorithm,which is suitable for the multi-input and multi-output system.Combined with the principle of LQG control algorithm,the AO system is modeled.The LQR regulator and Kalman filter are designed based on the state space model,and the AO system based on LQG controller is completed.At the same time,the application of LQG control algorithm in AO system is analyzed and verified by simulation,and the correction effect is compared with the traditional PI algorithm.3.Set up an experimental platform to conduct outdoor wavefront correction experiments with different transmission distances of 0.6km,1.0km and 5.0km.Take wavefront phase Zernike coefficient,wavefront peak-valley value,wavefront root-mean-square value and wavefront power spectral density as evaluation indexes.A large number of experimental data show that the AO system based on LQG controller has a good correction effect on distorted wavefront.In this paper,the application effect of LQG and PI control algorithms in AO system is verified by theoretical analysis,simulation and experiment.The experimental results show that both of them can correct wavefront distortion effectively,but the LQG algorithm can significantly improve the amount of computation,convergence speed,correction performance,noise frequency suppression and the adaptive ability of the AO system to the external environment.