Study On Visual Axis Stabilization Method Of UAV Optoelectronic System

When UAV reconnaissance and aiming at ground targets,the on-board photoelectric tracking system is usually disturbed by on-board vibration,attitude change and its own moving parts,other internal and external moments,which causes the visual axis shaking and the problem of target image shaking or unclear.In order to ensure that the visual axis stabilization platform of the photoelectric system is pointing stably in inertial space and isolating disturbance,it is necessary to take effective control methods to improve the stability performance of the system.This article around the unmanned aerial vehicle(uav)photoelectric optical axis stable platform system control method to carry out the research,focuses on the classical PID controller parameters of order and classical PID controller parameters,analyzing the setting method of fractional order PID controller is designed,respectively,and the BP neural network PID controller,meanwhile,it has a better control performance of the control algorithm for hardware implementation and performance test hardware system.The main contents of the study are as follows:(1)The structure,kinematics and dynamics of the visual-axis stabilized platform of the photoelectric system are analyzed and the system modeling is carried out.According to the performance requirements of the photoelectric system axis stabilization platform,the two-axis and two-frame stabilization structure was selected,the coordinate system among the base,pitch frame and azimuth frame was established,and the transformation matrix among the coordinate systems was deduced.Through the kinematics analysis of the stable platform structure,the dynamic models of the angular velocity,angular acceleration,moment of inertia and moment between the platform shafting systems are established.Through the analysis of the loop of the system,the mathematical model of the transfer function of each link of the loop is calculated,which lays a foundation for the design of the controller of the system.(2)The Fractional order PID control algorithm of visual axis stabilization platform of photoelectric system is studied.The order of differential and integral terms in the parameters of the classical PID controller is deeply analyzed and studied.According to the theory of fractional calculus,the fractional PID controller is designed by using Oustaloop approximate filtering method.Through the simulation experiment,it is verified that the fractional PID controller has more remarkable control performance compared with the classical PID controller.Aiming at external disturbance,the velocity-based disturbance observer(VDOB)was introduced into the visual axis stabilization loop,and a composite control method of fractional order PID and VDOB was designed.The simulation results show that VDOB can effectively isolate the disturbance of low frequency signal to the stability loop of the visual axis,and improve the control performance of the system.(3)The control algorithm of BP neural network PID for the platform stabilized by visual axis is researched.The method of parameter self-tuning of the classical PID controller is deeply analyzed and studied.The output value of the current mainstream BP neural network algorithm is taken as the parameter value of the PID controller,and the BP neural network PID controller is designed.By building a simulation experimental platform for simulation experiments,it is verified that compared with the classical PID controller,the BP neural network PID controller can realize the online automatic adjustment of parameters and improve the dynamic performance of the system.Finally,the control performance of fractional-order PID controller and BP neural network PID controller is compared through isolation degree,and the performance of fractional-order PID controller is better than that of BP neural network PID controller.(4)The Fractional-order PID control algorithm of visual axis stabilization is implemented on FPGA and the system verified by experiment.The fractional order PID control algorithm with excellent control performance is simplified,and the algorithm performance is realized on FPGA.Finally,the designed optical axis stabilized platform respectively from the hardware experiment test,swing,start-stop experiment test and stable precision test experimental verification,the experimental results show that the design of the method of fractional order PID control the stability of the accuracy of 46.1 urad,satisfies the requirement of system index,effectively improve the control performance of the visual axis stability system.