Research On Wide-Bandwidth And High-Precision Control Method For Line Of Sight Stabilization Of Airborne Photoelectric Payload

The airborne photoelectric payload(APP)has strong maneuverability,good time?liness and high resolution.It can carry out reconnaissance and detection,aiming and tracking,target positioning and radiation measurement of targets,and has a wide range of military applications.The APP obtains the image or video of the target through optical imaging,and the stable accuracy and bandwidth of line of sight(LOS)of the APP are conducive to clear imaging.In recent years,with the faster and faster flight speed of the aircraft,the detection distance of the APP is getting farther and farther,and the requirements for the stability accuracy and bandwidth of LOS of the APP are also getting higher and higher.Therefore,it has important engineering application value to study the LOS stability control method.This thesis takes strapdown APP of inertial sensors(hereafter referred to as strap-down APP,SAPP)as the object,studies the inertial stability control method of LOS in depth,aims to improve the accuracy and bandwidth of LOS stability of the APP,and expands the application of APPs in advanced airborne equipment.For the photoelectric payload control system with coarse-fine two-stage stability,the coarse stability based on frame servo and the fine stability based on piezoelectric micro-motion stage are studied,respectively,and the research is carried out from the following four aspects:(1)In order to effectively expand the bandwidth of the LOS stabilization control system of the APP and utilize the inertial motion information of the base,this paper takes the frame servo system of the SAPP as the research object,and establishes the SAPP model based on the multi-rigid body dynamics theory.Aiming at the problem that the vibration of strapdown inertial stabilization control system is easily caused by the base mounting structure effect and the coupling effect of base and load,the limitation that the conventional electromechanical model without considering the dynamic characteristics of the base is analyzed.Then,the effectiveness of the proposed model is verified by the simulation experiments combined with the dynamic model.(2)To effectively compensate for the disturbance of the frame servo system,the multi-source disturbance and the necessity of anti-disturbance of the APP is analyzed The friction torque and the coupling torque between the base and the load are regarded as a kind of friction-like torque,and its model is established through equivalent transfor-mation.According to the friction-like model,three disturbance compensation methods based on the feedforward of disturbance model,the feedback of disturbance model and disturbance observer are designed.Finally,the experiments verified the parameter iden-tification steps and verification procedures of the friction-like torque model.Under the conditions of different frequency commands,the angular velocity errors of various dis-turbance compensation methods are compared,and the characteristics of each method are summarized(3)In order to achieve a controller with oscillation suppression and disturbance compensation,a strapdown inertial stabilization controller is designed based on the three-step method for the friction-like torque and combined with the dynamics model of the SAPP.It includes an improved feedback controller,a feedforward controller based on angular velocity and angular acceleration of the base,and a compound disturbance compensation controller.The improved feedback controller is designed to suppress the possible oscillation of the strapdown inertial stabilization control system.The feed-forward controller based on the angular velocity and angular acceleration of the base effectively improves the dynamic performance of the control system.The compound disturbance observer adopts the method of friction-like model feedforward compensa-tion combined with the nonlinear disturbance observer,which makes the control system have strong disturbance suppression ability.Furthermore,the stability and convergence of the controller are proved.The comparative experiments results show the effectiveness and superiority of the proposed method in terms of command tracking performance and disturbance suppression performance(4)After the first stage stabilization of the APP frame as a coarse stabilization channel,the system still has a certain residual error.To achieve higher accuracy and bandwidth of the LOS stabilization control,a two-stage stabilization system based on piezoelectric micro-motion stage is added to the frame stabilization.To describe the hysteresis nonlinearity of piezoelectric micro-motion stage,a second-order dynamic hysteresis model of piezoelectric micro-motion stage is established based on the Bouc-Wen model and second-order linear system.And on this basis,an adaptive sliding mode control method is proposed,and the states of the control system is convergence by the finite time.An adaptive controller is added to the sliding mode controller,which is a switching function with adaptive gain.The switching gain is adjusted in real time to remove the uncertainty of model and parameters and external disturbance Finally,the experiments verified that the dynamic hysteresis model in describing the nonlinear characteristics of piezoelectric micro-motion stage is effective.Compared with proportional-integral control and sliding mode control algorithm,the results show that the proposed algorithm can achieve the smallest position tracking error under multiple frequencies command inputsThe proposed control method in this paper has been verified in the embedded platform,which provides theoretical support and design reference for the application of advanced control algorithm in the LOS inertia stabilization of the APP.