Deformation Analysis of a Hummingbird Inspired MAV Flapping Wing using Digital Image Correlation

Abstract

Flapping wing micro air vehicles (MAVs) have the advantage of being able to fly at slow speeds and have high maneuverability. The design of a flapping wing MAV inspired by birds presents many technical challenges because birds as natural fliers exhibit higher efficiency than any man made flapping wing structure. Thus, the structure and motion of bird wings provide a starting point for the study of flapping wing MAV. In order to compare the deflections of the fabricated wings with the complex mechanism of the bird wings, it is required to quantify these deflections. Both the bird wings and the fabricated wings are very light weight and, therefore extremely light weight sensors or non-contact methods are required for the measurements of the deflections. Digital image correlation (DIC) provides one such option. DIC is an optical noncontact method used to acquire displacements. A simple two dimensional DIC code has been developed and validated in this work. Design and fabrication of wings is based on the hummingbirds. A 3D tapered wing design was developed and used for development of mold. This mold was used for fabrication of flexible polypropylene wings. For flapping motion measurements of wings, a simple slider-crank mechanism was designed to generate an oscillatory motion using brushless DC motors and Arduino Board. For modal analysis, an electrodynamic shaker was used to vibrate the wing with patterns stuck over its surface at its natural frequencies and captured the motion using a high speed camera. The captured images were analyzed using the developed DIC code and mode shapes for 1st and 2nd modes were obtained. For capturing the motion of a wing, a high speed camera mounted on a suitably designed stand was used. The validation of modal analysis was done using commercial finite element analysis software Ansys.