Theoretical And Experimental Research On Biomimetic Flapping-wing Robot Aerodynamic Characteristic

Flapping wing flight is the common used flight mode by flying creatures of nature.Compared with the fixed-wing and rotary-wing flight mode, flapping-wing flight can generatelift and thrust simultaneously just relying on the wing’s flapp motion, but has the uniqueadvantages of high flight efficiency, high maneuverability and compact structure. Biomimeticflapping-wing robot is a new kind of micro air vehicle which imitates the flapping wing flightmode of flying creature, with integrating of micro electro mechanical system, micro powersystem, micro control system and other advanced technologies. It becomes the researchhotspot in recent years with the wide application prospects military or civilian field. However,to achieve a micro biomimetic flapping-wing flying robot with full flight performance offlying creatures is still unavailable, not only in terms of miniaturization of manufacturingtechnology, lightweight high-strength materials, new energy technology, the most important isthat the aerodynamics characteristics of flapping-wing flight are quite different. Flappingwing flow field is a low Reynolds number unsteady viscous flow, so the traditional steadyaerodynamics for fixed-wing or rotary-wing can no longer be used directly.Aimed to reveal flapping-wing flight unsteady aerodynamic theory, and apply it to thebiomimetic flapping-wing robot, the fundamental issues of flapping wing flight, airfoilaerodynamic characteristics and flapping-wing mechanism are studied systematically in thepaper. The main contributions of the paper are as follows:The aerodynamic performance for flapping wing flying creatures in nature is studied. Inbirds, as an example, from the body structure, feather structure, motion posture, drag control,and energy utilization, this paper comprehensively expounded the bird flying high liftperformance. The weight control, lift improvement, drag reduction and energy conservationare key issues in biomimetic flapping-wing flying robots design.Incompressible unsteady viscous flow equations for flapping wing are established, andthe discrete solution methods in spatial domain and time domain are given based on the finitevolume method. According to the solution methods, several typical flapping wing airfoil flowfields with different shapes and motion parameters, such as pitch angle, flight speed, flapfrequency, are calculated in detail. In order to obtain high flight performance, differentparameters and their combination are given according to different flight condition or attitude.Kinematic model and aerodynamic model for a biomimetic flapping wing robot imitatingbird are built up, and the improved strip theory is proposed to solve the aerodynamic force forflapping wing robot. The results of experiments and simulations coincide to each other basically and show the similar tendency of aerodynamics forces during downstroke andupstroke. The larger size flapping-wing flying robot flight tests also give the similarconclusion.According to the different movements of flapping wings of insects and birds, twoflapping wing mechanisms are designed. One is with the "8"-shaped tip trajectory imitatingsmall birds or insects. The other is a foldable flapping wing mechanisim during upstroke.Three-dimensional model simulation and motion analysis results show that the twomechanisms can produce high efficient flapping-wing movement.