The Design Technologies Of Biomimetic Wings For Flapping-Wing MAVs

Flapping-wing micro air vehicle (Flapping-wing MAV) is a new conceptualaircraft which mimic the flying modes of birds and insects, and can be widely used inthe fields of military and civil applications. It has small sizes, light weights, low costs,good stealth abilities and high maneuverability. Because of these advantages, it willbe researched more and more widely in the future. In this work, some keytechnologies and problems on the bionic wings design of flapping-wing MAV werestudied and discussed.From the point of view of bionics, the flying mechanism, flyingmode and theprinciple about flapping flight of birds and insects were studied respectively.The equations of motion for flapping-wing MAV, which have indicated thechanges of the moment and products of inertia for independent parts (such as bodyand wings), and the location changes of the center of mass for the total vehicle, wereestablished. Besides, a micro flapping-wing mechanism driven by 2 linear drivers wasdeveloped in terms of the configuration of insectile thorax. And the driving forcecurves, which are suitable meet all kinds of wingtip trajectorys, can be simulated bysolve the equations.Based on the equations of rigid wings, the equations of motion for flexibleflapping-wings were derived. Bend and torsion will appear clearly when the insectsflap their wings. These flexible deformation are important for aerodynamic force plus,energy saving and higher stability. Therefore, an idea that increase flapping angle andproduce torsion angle of wing by the flexible wing deformation under inertial forceand aerodynamic force, was conceived. With the help of finite element method (FEM),the idea was carried out by choosing proper flapping frequency when the figuration ofwing and layout of nervure is determined.A theory of flapping mechanism by sympathetic vibration was developed forflapping-wing, and the biomimetic wings design and modal optimization approachesassociated with this flapping" mechanisms were studied using FEM. The vibrationcharacteristics of some insect wings were determined by modeling these wings aslinearly elastic structures using finite elements. Then the characteristics of geometric shapes and the nervure position of biomimetic wings were sum up to support thesympathetic vibrated flapping mechanisms. In the foundation of the Biomimeticwing's model, the modal optimization method was studied, considering differentparameters such as asPect ratio and key node coordinates of wing's nervure.The unsteady aerodynamics associated with flapping flight modes offlapping-wing MAV was studied using method of computational fluid dynamics(CFD). A three dimensional moving wing model was built for the flapping MAV,which mimics biological locomotion. The Arbitrary Lagrangian Eulerian (ALE)method with ANSYS/CFD was used to solve the Navier-Stokes equations numerically.The solution provided the leading-edge vortices could generate enough lift to suppo.rta typical flapping MAV. In the foundation of the numerical simulation, the variationsof different parameters of the flapping MAV were studied, such as flapping amplitude,pitch amplitude and flapping frequency.The Fluid-Structure coupling mechanics for flexible flapping-wing had beenpreliminarily studied and discussed. According to the practically developed MAV, a2-D model for flexible flapping-wing had been established. Fluid-Structure couplingdeformation and the effects of this model on the aero dynamic performance wereanalyzed, which have offered a theoretical basis for design of the aerocraft withflexible flapping-wing.Based on the assumption of geometric similarity among birds and insects, thebionic design method for rigid and flexible flapping-wings was studied and alightweight flapping-wing MAV was build which can successful fly in the sky. Thenaerodynamic performance tests have been conducted for the manufactured rigid andflexible flapping-wings in a low turbulence and low Reynolds number wind tunnel ofNPU (Northwestern Polyechnical University). The test results proved that the liftperformance of flexible wing is better than rigid wing. The influence of flappingfrequency, wind velocity and angle of attack on aerodynamic characteristics wasinvestigated. In the foundation of the wind tunnel test, the compositive parts offlapping lift and their relations between each other were discussed. The test wassuccessful and the results could be helpful for the design of.flapping-wing MAV.