Modal analysis of an artificial wing mimicking an Allomyrina dichotoma beetle's hind wing for flapping-wing micro air vehicles by noncontact measurement techniques

Abstract

Recently, the development of flapping-wing micro air vehicles (FW-MAV) for operation in extreme environmental conditions has demanded properly designed, biologically inspired wings that can produce enough lift force to keep the vehicles aloft. The structural analysis of an artificial wing is carried out in the design of an FW-MAV. In this study, the dynamic characteristics of an artificial wing mimicking an Allomyrina dichotoma beetle's hind wing were investigated by a non-contact measurement method. The natural frequencies, mode shapes, and damping ratios of the first three basic vibration modes in the operating frequency range were determined using a Bruel & Kjaer (B&K) fast Fourier transform analyzer, along with a laser sensor. The laser sensor was used to obtain the displacement history of the marked points on the wing to calculate the frequency response function. To confirm the results, a three-dimensional digital image correlation (3D-DIC) method, as well as high speed digital cameras, were employed to construct the mode shapes of the wing when it was vibrated at a pre-determined natural frequency. The mode shapes by the DIC method showed good agreement with those by the laser displacement sensor. These results provide a method for the modal analysis of a light weight structure like an insect wing as well as for the construction of the mode shapes using DIC. The high speed 3D-DIC method, used successfully in mode shape measurements, can also be used to study the wing deformation of an insect during flight, which is challenging in an insect study.