Research On The Mechanism Design And Aerodynamic Analysis Of Flapping Wing Micro Air Vehicles

Flapping-wing air vehicle is a kind of aircraft that generates lift and thrust by imitating birds and insects.Compared with rotor aircraft and fixed wing aircraft,flapping wing aircraft is advantaged in small size,high agility and high concealment.Therefore,it has become a hot research topic.In this paper,a flapping-wing mechanism is designed that can imitate the movement of insect wings from the aspect of bionics,then,we analyze its aerodynamic characteristics and set up experimental research.These researches provide a new idea and beneficial supplement for the development of new micro-flapping wing air vehicle.The main research results are as follows:Firstly,the wing structure,flight characteristics and the mechanisms of generating high lift on birds and insects are analyzed,meanwhile,the differences of flight characteristics between birds and insects are summarized.Then,the difference of wingtip trajectory on birds and insects and its aerodynamic influence are introduced,which provide biological basis for designing the flapping-wing air vehicle.Finally,the kinematic parameters of the wings are defined.Based on the analysis of existing flapping-wing mechanism,and the combination of the mechanism synthesis and bionics,a spatial RURS mechanism that can output multi-dimensional motion through a single input is proposed.Denavit-Hartenberg parameters method is used to set up the kinematic model of the spatial four-bar mechanism.Then,genetic algorithm and nonlinear programming optimization algorithm are used to optimize the mechanism,which take the multi-dimensional flapping angle as the objective function,resultly,the mechanism parameters that are beneficial to flapping wing flight are obtained.Finally,an ADAMS simulation model of the mechanism is established,and the simulation result is in good agreement with the theoretical calculation.Based on the computational fluid dynamics method,the aerodynamic characteristics of the spatial figure-of-eight wingtip trajectory are analyzed.Fluent software is used as the simulation platform.A rigid model of the insect wing and the motion equations are established,then,the three-dimensional simulation process of the flapping wing movement is completed with the dynamic grid technology.The results show that the spatial figure-of-eight wingtip trajectory can generate positive lift force continuously in the hovering flight,also,the spatial figure-of-eight movement can generate the leading edge vortex and other high lift mechanism.The influence of flapping wing frequency,flapping plane angle and wingspan on aerodynamic characteristics in the forward flight are analyzed,which provide theoretical guidance for the prototype design.Finally,the parameters of flapping-wing micro air vehicle are given based on bionic scaling,meanwhile,the driving mechanism,flexible wing and overall structure of air vehicle are designed.The prototype is fabricated by means of 3D printing and other processing methods.High-speed camera and three-dimensional force sensor are used to set up the experimental system,then we complete the experimental test.The influence of flapping wing frequency,wind speed and other parameters on the lift and thrust characteristics of the flexible wing prototype are analyzed,which provide valuable reference for the development of flapping wing air vehicle.