Advanced Biologically-Inspired Flapping Wing Structure Development

Abstract

This study examines the possibility to develop a manufacturing method to build a complicated composite structure comparable to insect wings. Stimulated by the research in flapping wing micro air vehicles, a wing structure that can be controlled with stiffness and mass distribution during manufacturing can enable complicated kinematics and efficient aerodynamics. Insects demonstrate superior flight performance and therefore their wings are good examples for building an artificial counterpart. Cicada wings are selected in this work for emulation. An artificial composite wing is built with computer numerical controlled tooling and manual fabrication, with similar vein pattern. The wings are compared with measurements of mass distribution in the spanwise direction. The results show that the composite reinforcement topology and cross section variation allow the two wings to have very similar property trends. Several difficulties are overcome in this work: replicating the cicada wing vein pattern, fabricating small composite structure components and measuring their weight distribution. I. IntroductionIn flapping wing aircraft research, researchers have paid much attention to understanding the mechanisms that govern flapping flight. Some researchers think that the wing flapping kinematics is a dominant factor in the lift generation [1], and others believe that the wing geometry and mechanical prosperities are critical [2][3]. The natural insect wing structure can be measured down to the minutest detail by a three dimensional curve-shaped measuring system [4], this provides a very good reference for the biologically inspired flapping wing fabrication process presented in this work.The deformation of the flapping wing is a key factor in flight performance since it affects airflow around the wing and the consequent aerodynamic forces. Fabricating a biologically-inspired artificial flapping wing can be an effective way to understand the morphological function of the insect wing [5].Flying insects in nature are the best example for a high performance artificial aircraft with flapping wings. A natural insect wing has very complex vein patterns, such as the cicada wing shown in Figure 1.If the vein of flapping wing skeleton is considered as a beam, its mechanical property would be dominated by the cross-section profile. The height variation of the cross-section determines the area moment of inertia, which consequently affect the bending/torsional performance of the wing. The area variation of the cross-section also results in non-uniform mass distribution across the wing. During flapping motion, therefore, this mass distribution would affect the wing deformation caused by inertia. In order to optimize the flapping wing aerodynamic performance, a method for creating an artificial flapping wing with complex vein pattern and variable cross-section needs to be developed.