Micro Air Vehicles are a class of extremely miniature unmanned aerial vehicles (UAV) that can be small enough to be held in the palm of a hand. Because of their size, MAV designers often try to mimic the flight of small birds or insects. For the first time, an MAV design is using wings inspired by bats.
Wind tunnel tests using high-speed video cameras have finally unlocked the secrets of the unusual wing movements that give bats flight. Flexible skin membranes are stretched over multi-jointed limbs, giving bats wings that shift shapes with the wind, resulting in greater lift, lesser drag, increased maneuverability and superior efficiency to birds, not to mention man-made aircraft.
So how do you turn bat wings into MAV wings? According to their press release, Professor Bharath Ganapathisubramani of Southampton’s Aerodynamics and Flight Mechanics Group and his team used the wind tunnel videos to develop computer models of the bat wing movements. To make the wing shift shapes, it’s made from electro-active polymers that shrink or stretch when specific voltages are applied, allowing them to strengthen or relax during flight. Dr. Rafael Palacios, a team member from Imperial College London, describes how it works.
Instead of a traditional approach of scaling down existing aircraft design methods, we constantly change the membrane shape under varying wind conditions to optimise its aerodynamic performance.
While the wings mimic a bat, the MAV itself looks nothing like the flying creature. The 0.5m-wide (20 inches) vehicle is more like a hovercraft. In fact, it takes off and lands on water rather than on land. The test was just to prove that the wing works. The next step will be to modify it for more conventional MAVs.
So it’s not so much the shape of a bat’s wing but the way it shape-shifts that has made what Professor Ganapathisubramani calls a “paradigm shift in the approach to MAV design.”
We've successfully demonstrated the fundamental feasibility of MAVs incorporating wings that respond to their environment, just like those of the bats that have fueled our thinking. We've also shown in laboratory trials that active wings can dramatically alter the performance. The combined computational and experimental approach that characterized the project is unique in the field of bio-inspired MAV design.
If they can figure out a way for the bat-inspired MAVs to eat as many insects as the real thing, they’ll sell millions of them.