Research On Control Method Of Visual Axis Stability For Airborne Photoelectric Stabilized Platform

As a kind of advanced equipment integrating optics,precision machinery,image acquisition and processing,automatic control and other fields,airborne photoelectric stabilized platform is used to isolate interference from the outside,so as to ensure that the photoelectric detection equipment can complete the targeting,capture and tracking of the target.Because it will be affected by many disturbance factors in its work,Therefore,in order to improve the robustness and disturbance suppression ability of the airborne optoelectronic stabilized platform,the visual axis stability control strategy based on the airborne optoelectronic stabilized platform is studied in this paper.The main research work and innovative achievements of this thesis are as follows:The components and basic working mode of the airborne photoelectric stabilized platform are explored,and the mechanism model of the system is established.The influence of disturbance factors such as model uncertainty,torque disturbance and attitude disturbance on the stability accuracy of the axis of sight of airborne photoelectric stabilized platform is analyzed.The basic principles and design ideas of PID control,sliding mode control and linear active disturbance rejection control are studied,and the limitations of the above control methods are analyzed.The speed ring model of airborne photoelectric stabilized platform is taken as the controlled object.A speed servo control system based on traditional sliding mode controller,PID controller,sliding mode controller based on fast power reaching law and linear active disturbance rejection controller is designed,and simulation experiments are carried out,and the experimental results are analyzed,which provides a theoretical basis for the improvement of the control strategy.In order to improve the robustness and stability accuracy of airborne photoelectric stabilized platform in working environment,a sliding mode active disturbance rejection control strategy based on fast power reaching law is proposed based on the analysis of disturbance estimation principle and limitation of linear extended state observer.Firstly,in order to achieve chattering suppression,the fast power reaching law is adopted in the design controller.Secondly,considering that the measurement noise of the system sensor is inevitable in the engineering field,the bandwidth of the linear extended state observer will be limited.When the frequency of external disturbance increases,the bandwidth limitation will lead to the increase of the total disturbance estimation error and interference stability boundary,and the stability accuracy of the system’s apparent axis will be reduced.Therefore,the fast power reaching law is modified in this paper.When the error increases,the coefficient of the power term also changes with the error,so the system can always maintain a high accuracy.Then,using Lyapunov method to analyze the stability of the system.Finally,the simulation results verify the superiority of the sliding mode active disturbance rejection control strategy based on the fast power reaching law.When the linear sliding mode surface is used to establish the controller,the system state cannot converge to the equilibrium point in the sliding stage.For accelerating the convergence rate of the system state in the sliding stage,a fuzzy fast non-singular terminal sliding mode active disturbance rejection control strategy is proposed.Firstly,a fast non-singular terminal sliding mode surface is designed,and on this basis,fuzzy logic is introduced to improve the fast power reaching law,so that the controller parameters can adjust themselves according to the system error changes.Then,the Lyapunov method is used for analyzing the stability of the system.Finally,the simulation results demonstrate the superiority of the method proposed by this thesis.For solving the defect of low state estimation efficiency of linear extended observer,a variable gain extended state observer is proposed and its stability is analyzed.A saturation function is introduced in the design of variable gain extended state observer.Since the gain of variable gain extended state observer can decrease rapidly when the error of state estimation converges,the estimation efficiency of each state can be improved without increasing the degree of noise influence of the state estimate.The effectiveness of the proposed variable gain extended state observer is verified by simulation experiments.