US Air Force Funded Researchers Study Bats to Enhance Micro Air Vehicles

Researchers from several universities are studying how the biological attributes of flapping and flexible flight demonstrated by birds, bats and insects can improve future micro air vehicle systems. This research has led to the creation of engineering models, such as the one illustrated in this graphic. (Courtesy graphic.)

Focus on Defense:

ARLINGTON, Va., Jan. 7, 2009 -- U.S. Air Force-funded researchers from several universities are studying the flexible, flapping wings routinely used by bats and insects and mimicking their biological attributes to improve agility, speed and adaptability in micro air vehicle systems.

Air Force Office of Scientific Research officials here manage two projects on biologically-inspired flight.

Both are part of the 2007 Multidisciplinary University Research Initiative, which provides funding for topics that rely on expertise in multiple disciplines.

Dr. Kenny Breuer, a fluid mechanics professor from Brown University, and Dr. Wei Shyy, an aerospace engineering professor from the University of Michigan, each lead a Multidisciplinary University Research Initiative project. Though their respective teams focus on different biological and engineering aspects of this problem, they share the same overall goal of understanding bat flight and its potential applications to micro air vehicles.

"Future micro air vehicles will need to be agile, robust and maneuverable, and our research will provide some guidance as to how we might incorporate these features using inspiration from biology," Dr. Breuer said.

If successfully transitioned, this research could lead to small, remote controlled aircraft that can move in complex environments such as forests, interiors of buildings, caves or tunnels.

Birds, bats and insects have some highly varied mechanical properties that researchers have not incorporated in engineering, Dr. Shyy said.

"They're not only lighter, but they also have more adaptive structures," he said. "These natural flyers have outstanding capabilities to remain airborne through wind gusts, rain and snow."

Facing many of the same challenges posed by this complex, biological system, Dr. Breuer is working on a variety of efforts to unlock the mystery. One such effort involves capturing video footage of bats flying in a wind tunnel and measuring the fluid velocities in their wakes. Another involves studying flight properties in different environments and among different species of bats.

The results of these experiments and others have allowed Dr. Breuer to construct engineering models that mimic specific features found in bat flight.

His Multidisciplinary University Research Initiative partners from Oregon State University, Massachusetts Institute of Technology and the University of Maryland are also doing innovative research. They are developing computational methods for simulating complex, moving, flexible structures; mapping the neurophysiology of bat sensor and motor systems; and creating control systems that might be of use in micro air vehicle technologies.

Dr. Shyy's team, comprised of faculty and students from the University of Michigan as well as colleagues from the Universities of Florida and Maryland, is focusing on hovering and forward flight modes of micro air vehicles.

"Birds, bats and insects can fly in turbulent environments with fast, unpredictable wind gusts," Dr. Shyy said. "Yet, they can react almost instantaneously and adapt with their flexible wings."

Knowing this, his team has placed particular emphasis on learning how and why flexible wing structures affect lift and thrust generation, especially in unsteady environments.

"If handled appropriately, flexible wing structures can delay stall, enhance stability and increase thrust," Dr. Shyy said.

(Report by by Molly Lachance, U.S. Air Force Office of Scientific Research.)

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