Design Of A Small Tail-sitter UAV With Foldable Wings

In recent years,vertical take-off and landing(VTOL)fixed-wing unmanned aerial vehicles(UAV)has become a research hotspot in the field of UAV.As a kind of vertical take-off and landing fixed-wing UAV,tail-sitter UAV integrates the advantages of both fixed-wing UAVs and rotary UAVs,which can take off and land vertically and cruise at high speed.It has a wide application prospect in military and civil fields.To solve the problems of the traditional tail-sitter UAV,such as poor wind resistance during take-off and landing and poor wing size and portability,a tail-sitter UAV with foldable wings has been designed in this thesis.Firstly,according to the design requirements,the overall layout of the tail-sitter UAV has been come up with,which consists of the joined-wing aerodynamic layout and coaxial twin-propeller vector dynamic system.In addition,the genetic algorithm was used to optimize the size of the joined-wing.The overall parameters of the UAV have been designed step by step,and the overall design scheme was completed.Then,the ANSYS-Fluent software was applied to carry out aerodynamic simulation of the tail-sitter UAV,and the lift-drag characteristics and pitch characteristics of the UAV in fixed-wing flight mode were analyzed.The horizontal flight performance indexes were obtained through calculation,and the coupling forces of the wings and aerodynamics were calculated.Afterwards,the folding-wing mechanism,fuselage structure and tail structure were designed in detail.Finally,this thesis analyzed the cruise flight mode and the transition flight mode.And the flight dynamics model was established by deriving the kinematic and dynamic equations of the tail-sitter UAV.The control modes of the vertical take-off and landing(VTOL)flight mode,transition flight mode and fixed-wing flight mode were analyzed,which laid a foundation for the design of flight control system.