Soon, bat-inspired flying robots

Scientists, including one of Indian-origin, are planning to develop small flying vehicles with flapping wings inspired by wing motions of a bat.
Researchers at Virginia Tech in US are studying how bats are able to fly by flapping their wings and will apply that knowledge toward designing small flying vehicles known as "micro air vehicles".
More than 1,000 species of bats have hand membrane wings, meaning that their fingers are essentially "webbed" and connected by a flexible membrane.
But understanding how bats use their wings to manipulate the air around them is extremely challenging - primarily because both experimental measurements on live creatures and the related computer analysis are quite complex.

In the study of fruit bat wings, researchers used experimental measurements of the movements of the bats' wings in real flight, and then used analysis software to see the direct relationship between wing motion and airflow around the bat wing.
"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, the William S Cross professor in the Department of Mechanical Engineering and director of the High Performance Computational Fluid Thermal Science and Engineering Lab at Virginia Tech.

Researchers found bats manipulated the wing motion with correct timing to maximise the forces generated by the wing.

"It distorts its wing shape and size continuously during flapping," Tafti noted.
For example, it increases the area of the wing by about 30 per cent to maximise favourable forces during the downward movement of the wing, and it decreases the area by a similar amount on the way up to minimise unfavourable forces.
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, co-author of the study.

"Next, we'd like to explore deconstructing the seemingly complex motion of the bat wing into simpler motions, which is necessary to make a bat-inspired flying robot," he said.
"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?" Tafti added.
The findings are published in the journal Physics of Fluids.