Design Of UAV Visual Axis Stability Control System

In the process of performing tasks unmanned aerial vehicle(UAV)photoelectric target detection and tracking system is easily affected by the attitude change of the carrier and the disturbance of the platform itself,which results in the vibration of the line-of-sight and blurred image,thus affecting the accuracy of the acquisition,aiming and tracking of the target by the photoelectric target detection system.Therefore,it is necessary to take effective control algorithm to improve the stability of the line of sight of the system.In this paper,the design and control circuit implementation of the optical axis stabilization controller for UAV are studied.The main contents of the study are as follows:(1)According to the optical mechanical structure of the photoelectric target tracking system,the coordinate systems of the base,pitch frame and azimuth frame of the system platform are established.The transformation matrix between coordinate systems is deduced and the kinematic and dynamic models of two frame photoelectric systems are established,to obtain the relationship between angular velocity,angular acceleration,moment of inertia and moment of shaft system.This lays the foundation for the design of the line-of-sight stabilization controller.(2)The transfer function of each link in the line-of-sight stabilization loop is established,and the structure of fuzzy PID stabilization controller with self-tuning parameters is designed.The simulation comparison verifies that the fuzzy PID controller has better control performance than the classical PID controller.Considering the factor that the carrier rate disturbance affects the stability accuracy,the rate disturbance observer(VDOB)is introduced into the line-of-sight stability loop,and construct a composite controller with parameter self-tuning fuzzy PID and VDOB.The simulation results verify that the introduction of VDOB into the stability control system can significantly improve the isolation effect of the control system to low frequency disturbance signals and the performance of the control system.(3)To solve the problem that the output signal noise of the optic axis stabilization loop micro electro mechanical systems(MEMS)gyroscope is large and affects the accuracy of the optic axis stabilization,the method of de-noising of the MEMS gyroscope is studied.The reason of the gyro temperature drift is analyzed,and the Kalman-AR model of the gyro signal filtering is established to reduce the noise of the gyro signal,and the temperature drift of the MEMS gyroscope is compensated by using the compensation method of the optimized BP network with particle swarm optimization(PSO).The control precision of the line-of-sight stabilization system is improved.(4)The hardware circuit of the visual axis stabilization controller based on the FPGA is designed and implemented.Includes: power module,communication module,driver module and data acquisition module.The control system software is designed.(5)The control system is verified by simulation and experimentally.The simulation results show that the performance of the control system is improved effectively by the composite controller built by the combination of parameter self-tuning fuzzy PID and VDOB.The stability control system experimental results show that the stability accuracy of the line-of-sight stabilization control system is 46.1μrad,to satisfies system index requirements.