Fruit Bat Inspired Flying Robot Designed by Virginia Tech Researchers

Researchers are planning on developing small flying machines inspired by the unique aerodynamic features of a fruit bat and other flying creatures.

Close observations on how fruit bats flap their wings to manipulate the air around them, inspired researchers at Virginia Tech to design small flying robots, complete with flapping wings.

More than 1000 species of bats have wings made of webbed flexible membranes, which connect their fingers. To study wing movements, researchers collected measurements of flying bats and analyzed them with the help of a software to determine the relationship between wing motion and airflow.

"Bats have different wing shapes and sizes, depending on their evolutionary function. Typically, bats are very agile and can change their flight path very quickly -- showing high maneuverability for midflight prey capture, so it's of interest to know how they do this," said Danesh Tafti, director of the High Performance Computational Fluid Thermal Science and Engineering Lab at Virginia Tech.

Fruit bats, Cynopterus brachyotis, have a straight-line flapping motion. A typical fruit bat weighs nearly 30 grams with their extended wing reaching nearly 17-19 centimeters in length. The researchers were surprised to see that despite its small size, the creature manipulates wing motions according to the force needed to move upwards or downwards.

The scientists noticed that while moving down, the bat increases the area of the wing by almost 30 percent in order to maximize favorable force. However, it reduces the area of its wing by 30 percent on its way up to lower unfavorable force.

"The force coefficients generated by the wing are "about two to three times greater than a static airfoil wing used for large airplanes," said Kamal Viswanath, a co-author who was a graduate research assistant working with Tafti.

This finding is the first step towards making micro air vehicles. The researchers now plan to deconstruct the complex motion of the bat wings and convert them into simpler motions to make bat inspired flying bots.

"We'd also like to explore other bat wing motions, such as a bat in level flight or a bat trying to maneuver quickly to answer questions, including: What are the differences in wing motion and how do they translate to air movement and forces that the bat generates? And finally, how can we use this knowledge to control the flight of an autonomous flying vehicle?" added Tafti who is also a professor in the Department of Mechanical Engineering.

The finding was reported in the journal Physics of Fluids.