Robots may get their wings with a little help from bats.
According to a new study published in the journal Physics of Fluids, researchers observed how bats flap their wings to gain inspiration for designing small flying vehicles called “micro air vehicles.” A Virginia Tech researcher studied the wing movements of fruit bats to examine the relationship between their wing motion and the flow of air around their wings.
"Bats have different wing shapes and sizes, depending on their evolutionary function," Danesh Tafti, a mechanical engineering professor and the director of the High Performance Computational Fluid Thermal Science and Engineering Lab at Virginia Tech, said in a statement. "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."
More than 1,000 species of bats have hand membrane wings, which means their fingers are webbed to create a wing. Understanding how bats manipulate their wings to make a “straight-line flapping motion” could be a difficult task. The Virginia Tech researchers used experimental measurements of the bats’ wings in real flight and analysis software to understand their movement.
The researchers were surprised to discover that bats manipulate their wing motion with correct timing to maximize the force generated by the wing. "It distorts its wing shape and size continuously during flapping," Tafti said.
In other words, a bat could increase the area of the wing by about 30 percent to maximize favorable forces during the downward movement. This ability is "about two to three times greater than a static airfoil wing used for large airplanes," Kamal Viswanath, a study co-author, said.
This technique could be used to design future robots that can imitate these efficient flapping motions, researchers said. "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," Viswanath said.
Researchers also want to study other kinds of bat wing movements to keep wing design simple, but while maintaining the same relative force production exhibited by a real bat.
"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 said.