Accurate Tracking Control Of Aerial Refueling Based On Vision

Aerial refueling can extend the range,shorten the response times,and increase the flight time of UAVs.This thesis has studied the flight-control system of UAVs,the problem of tankers’trajectory tracking,the problem of image optimization in visual navigation,the algorithm of pose estimation and the formation flight of tanker and receiver in autonomous aerial refueling process.Firstly,the specific flight process of the tanker and the receiver in the process of autonomous aerial refueling is analyzed.A six-degree-of-freedom non-linear mathematical model of the UAV is established and a visual processing scheme is proposed,which lays a foundation for the follow-up research work.Secondly,designing the control law of tanker by using traditional control method and improving the L₁ trajectory tracking guidance law.The flight control system of the tanker is designed and simulated by classical control method based on the target tracking of the tanker trajectory.The improved L₁ trajectory tracking guidance law is used to design the guidance law of the tanker tracking trajectory,and compared with the traditional L₁ trajectory tracking guidance law.Finally,the digital simulation is carried out to verify the control effect.Thirdly,preprocessing the recognition image and fusing SP algorithm with traditional pose estimation algorithm for relative pose estimation.Aiming at the problem of recognizing the position of the cone sleeve of the receiver,a visual processing scheme based on the visual recognition points is proposed.The image is optimized by using the image preprocessing scheme and the feature points are collected.For pose estimation problem,traditional pose estimation algorithm is used to estimate the position and attitude of the cone sleeve.Aiming at the shortcomings of the traditional iterative algorithm,the algorithm is improved.The performance of the algorithm is compared and analyzed by the position and attitude errors of the two algorithms.Finally,the control law of the receiver is designed by using the method of time-scale separation and the line-of-sight method is used as the guidance law for the receiver to track the tanker.Based on the relative space distance and line-of-sight angle between the receiver and the tanker,the guidance law of the receiver tracking tanker is designed based on line-of-sight method,and the flight control system of the receiver is designed by time-scale separation method.The control effect of the guidance law and the flight control system is verified by digital simulation.