| The Four-rotor UAV,which integrates computer vision technology,microprocessor technology and VLSI technology,has the advantages of low cost,vertical takeoff and landing,and good maneuverability.It has been widely used and deeply studied in civil fields such as aerial photography,plant protection,logistics,Power Patrol and so on.The landmark-free landing method based on vision has become a research hotspot of Four-rotor UAV because of its better adaptability.Aiming at landmark-free landing method of Four-rotor UAV,this paper focuses on the construction of visual landing unit,landform image detection method and safe landing strategy of UAV.The main research contents are as follows:(1)The visual landing unit is constructed,the characteristics of UAV aerial photography image are studied,the structure and optical path settings of the visual landing unit are analyzed,the overall scheme of the visual system is put forward,the hardware parameters and selection of the visual system are determined,which paves the way for the following chapters to study UAV landing without landmarks based on visual image processing.(2)The image detection method is studied.The UAV landing scene is briefly analyzed.The detection methods of water and vegetation in the detection process of large-scale safety zone are studied.At the same time,the surface obstacles in the detection of small-scale safety zone are mainly studied.The detection method provides theoretical support for the study of landmark-free landing methods.(3)The safe landing strategy of UAV is studied.According to the analysis of Chapter 23,the conditions of safe landing are established.The transformation between the pixel coordinate system and the world coordinate system is introduced.The strategy of safe landing is analyzed from two aspects: the location of obstacle area and the selection of safe area.(4)Using the visual aided UAV platform,relevant test experiments and landing experiments are carried out,which verify the feasibility of this method. |
