Micro Air Vehicles Design Based On Bat Flight
Micro Air Vehicles, a type of unmanned UAV that boast incredibly small sizes, are often used for observation of hazardous spaces that are normally inaccessible to ground-oriented vehicles. They can be as small as 6 inches (15 cm), and serve multiple additional purposes.
A research project from the Engineering and Physical Sciences Research Council recently led to the development of a new breed of MAVs that are not only more aerodynamic and capable of long-distance flight, but are more economical to use. The new class of MAV was inspired by bat flight, where the wings can take different shapes based on the forces experienced. They also contain no mechanical parts, making them easy to maintain, according to a news release.
The wings' unique design uses electroactive polymers that enhance performance by being capable of stiffening and relaxing the wings in response to a voltage applied to them. As the voltage input changes, the shape of the membrane that makes up the wings alters, allowing in-flight alteration of the aerodynamics. This provides an avenue to flight distances that have yet to be achieved by MAVs.
The wings were developed by teams from the University of Southampton, which provided hands-on experiements, and the Imperial College London, which did the computational research. The U.S. Air Force and the European Office of Aerospace Research and Development also provided support.
The focus from Southampton and the Imperial College teams was on the mimicking of bat physiology. Bats are the only mammals capable of natural, genuine flight, making them an interesting concept to build on. The Imperial College London team used computational models to speed up the never-before-attempted design process early on.
"No-one has tried to simulate the in-flight behavior of actuated bat-like wings before, so we had to go back to fundamentals, develop the mathematical models and build the multiphysics simulation software we needed from scratch," Rafael Palacios, of the Department of Aeronautics at Imperial College London, said. "We had to make sure it could model not only the wings themselves but also the aerodynamic flows around them and the effect of the electric field generated across them."
The Southampton team used the findings to develop a 20-inch (0.5 m) wide test MAV designed to skim over the ocean's surface. The vehicle was put through extensive wind tunnel testing, and was successfully tested at nearby coastal location.
"This is a paradigm shift in the approach to MAV design. Instead of a traditional approach of scaling down existing aircraft design methods, we constantly change the membrane shape under varying wind conditions to optimize its aerodynamic performance," Palacios said.
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