Structural Design And Aerodynamic Characteristics Simulation Of A Two-stage Bionic Flapping-wing Vehicle

With the emergence and rapid development of bionics,a new branch of aircraft research-bionic flapping wing aircraft has emerged.Different from previous aircraft research,bionic flapping wing aircraft has the characteristics of flexibility,high concealment and excellent aerodynamic characteristics,so it has good application prospects in battlefield reconnaissance,fixed point blasting and other fields.At present,flapping wing aircrafts with mature technology mostly have single section wings.Although the processing and manufacturing of aircrafts are relatively simple,the bionics of flight attitude is poor.In order to improve the above problems,a two-stage flapping wing aircraft with passive bending wings is developed in this project.The specific research contents are as follows.First of all,taking large birds as the research focus,this paper analyzes the ground skeleton,feathers,flight process and the movement posture of birds’ wings,comprehensively explains the posture change and force process of large two-stage birds,and comprehensively summarizes the high lift mechanism of two-stage birds in combination with the research of aerodynamics.According to the bionic scaling law formula of flying creatures,the span,aspect ratio,wing load,flapping frequency and other design parameters of the two-stage flapping wing prototype are formulated.The whole scheme design of the prototype is completed,including the design of drive,deceleration,flapping wing,tail wing and passive folding scheme.The folding mechanism,flapping wing drive mechanism and hybrid scissors V-tail mechanism of the two-stage flapping wing robot are designed,and the kinematics equations of the flapping wing robot are established.Based on ADAMS software,the kinematics simulation of the virtual prototype is carried out,and the motion characteristic curves of the key components are obtained.The simulation results are in line with expectations.The movement curve of the prototype wing conforms to the flight process of large two-stage birds,and has good bionics.CFD analysis software Fluent is used to simulate the unsteady aerodynamics of the virtual prototype at low Reynolds number,and the lift and thrust coefficient curves under different flight conditions in the flapping process of the wing are obtained.The experimental results meet the expectations and conform to the flapping wing motion law.The design scheme has good aerodynamic characteristics,and the prototype can fly.Finally,under the guidance of the above theory,the prototype of the two-stage flapping wing is completed.The prototype was tested in the open air.The test results show that its flight action is closer to the real birds,and the aerodynamic performance of the two-stage flapping wing aircraft,such as thrust lift ratio and anti-interference ability,is better than that of the single-stage flapping wing aircraft.