Dynamic Design And Optimization Of Bionic Flapping-wing Aircraft For Multi-Attitude

The bionic flapping wing aircraft is a new concept aircraft which integrates multidisciplinary design.It has the characteristics of light weight,strong concealment,flexible flight and good stability.At the same time,flapping wing aircraft has broad application prospects in civil and national defense fields.Therefore,it is of great significance to promote the development of flapping wing aircraft.In flapping wing aircraft,the most important thing is the design of wing shape and driving mechanism.Aiming at the shortcomings of the existing multi-degree-of-freedom flapping wing mechanism,such as simple structure,too much driving motors and poor bionic performance,this paper proposes a three-section flapping wing model,and designs a multi-link flapping-wing mechanism which can simultaneously achieve flapping and double folding motions.Kinematics and dynamics of multi-link mechanism are analyzed.The main research contents of this paper include the following parts:First,on the basis of biomimetic research on birds,the wing movement characteristics and high lift mechanism of birds are expounded from the aspects of body structure,flight modes and wing movement modes.Based on this,the scheme of bionic flapping-wing mechanism is designed,and a bionic three-section flapping-wing model with better flight performance is proposed.A multi-link flapping-wing mechanism is designed,which can realize flapping and double-folding motions.Kinematics and dynamics of the multi-link mechanism are analyzed.Second,a three-section flapping wing model is constructed according to the shape of birds,and a three-section multi-degree-of-freedom motion model is established to realize "flapping-pitching-double folding".On this basis,the three-dimensional numerical simulation of flapping wing aircraft is carried out under the condition of low Reynolds number unsteady flow field by using simulation software,and the aerodynamic characteristics are analyzed.The flapping-wing aircraft is simulated from the view of flow field nephogram and the wing flow field.The influence of the flapping process on the flow field around the flapping wing is analyzed from the aspects of the spanwise pressure nephogram,the spanwise velocity nephogram,the whole-body isovorticity nephogram and the fuselage static pressure nephogram.The influence of the attack angle,the flapping frequency and the inflow velocity,the maximum flapping angle,the first folding angle and the second folding angle on the lift and thrust coefficients of the flow field is also analyzed.The law is explained theoretically.Finally,the flapping wing model is optimized in three typical flight states: climbing,cruising and diving,and the theoretical optimal solutions of aerodynamic parameters in different flight states are obtained.The theoretical optimal solutions are substituted for the corresponding simulation parameters in three-dimensional numerical simulation to verify the reliability of the optimal solution calculation.The design of bionic three-section flapping wing mechanism and its kinematics and aerodynamic characteristics analysis have important theoretical and practical significance for adapting to various flight postures and improving the overall performance of aircraft.