Bio-inspired flapping UAV design: a university perspective

Abstract

ABSTRACT Bio-inspired design to make artificial fla ppers fly does not just imitate biological systems as closely as possible, but also transferring the flappers’ own functionalities to engineering solutions. This paper summarizes some key technical issues and the states-of-art of bio-inspired design of flapping UAVs with an introduction to authors’ recent research results in this field. Keywords: Bio-inspired, Flapping-wing, Aerodynamic Model, Fluid-Structure Interaction, Flight Dynamics 1. INTRODUCTION The flapping flight of birds, bats, and insects has fascinated many researchers in various fields such as biology, zoology, aerodynamics, and electronics because of their highly efficien t maneuverability and aerodynamic benefits especially in a low Reynolds number flight regime. For many centuries, numerous efforts have been made to mimic nature’s fliers in order to make artificial flapping-wing vehicles. It is well known that most of the early trials for “flying machines” adopted flapping mechanism for generating thrust and/or lift; typical examples of the early design of flapping vehicles can be seen in the sketches of da Vinci and Cayley. It seem ed that the flapping vehicles were being forgotten with the great success of fixed wing aviation. However, we now see the rebirth of flapping flying machines in much smaller devices, namely flapping unmanned aerial vehicles (UAV). Equipped with a small video camera and various sensors, they can be used for surveillance and reconnaissance missions with quite perfect camouflage due to their inherent natural like shapes. More difficult or complicated technology issues are involved in the development of flapping UAV compared with their fixed or rotary wing type counterparts. In terms of payload carrying capacity and flight controls, the current flapping UAV need to be further improved. Birds and insects are the most efficient and outstanding flying objects, resulting from over 150 million years of evolutionary processes. However, bio-inspired design to make artificial flappers fly does not just imitate biological systems as closely as possible, but also transfers their own functionalities to engineering solutions. This paper summarizes some key technical issues and the state-of-art of bio-inspired design of flapping UAV with the introduction of the author’s recent results in this field. As with all other engineering, the development of integrated system engineering is essential for the development of successful flapping UAV, and the following items should be considered: 1.) an efficient aerodynamic model for low Reynolds number flow, 2.) design considering fluid-structure interaction, 3.) a bio-inspired design of flapping-wing motion mechanism, 4.) robust flight navigation and control, and 5.) miniaturized electronics and a micro power source. These items are in many cases tightly linked to each other. One typical example is the structural flexibility of a flapping-wing. Actually, biological flyers, especially insects, have spanwise-chordwise anisotropic flexible wings, and use complicated wing motions, such as flapping, twisting, folding, or rotating motions. The artificial flyers also have very thin and flexible wings structurally similar to those of the nature’s flyers, but they use mainly the flapping and passive twisting motions generated by the wing flexibility. The deformation of these flapping wings is strongly coupled with aerodynamic forces generated by the wing motion. At the same time, the structural deformation and the resulting flexible wing aerodynamics strongly influence the flight stability and controllability of flapping UAV.