The way bats move while in flight could serve as an the inspiration for a new generation of flying robots, according to a study recently published by Danesh Tafti and Kamal Viswanath.
Researchers have been studying how fruit bats use their wings to control the air around them. An understanding of the process behind how bats remain in flight could, in turn, help them to design a new generation of flying robots. These "micro air vehicles" would have small, motorized wings they would use to keep themselves aloft.
"Bats have different wing shapes and sizes, depending on their evolutionary function," explained Danesh Tafti, a professor in the Department of Mechanical Engineering at the High Performance Computational Fluid Thermal Science and Engineering Lab at Virginia Tech. "Typically, bats are very agile and can change their flight path very quickly - showing high maneuverability for midflight prey capture. It's of interest to know how they do this."
There are more than 1,000 species of bats, all of which sport wings composed of flexible webbed membranes connecting their 'fingers' together. Fruit bats in particular typically weigh around an ounce, with a wingspan of about seventeen centimeters, explained Tafti. In order to examine their flight techniques, Tafti and her team collected measurements of the bats in flight, using specially designed software to analyze how the animals' movements related to the motion of the airflow around their wings.
Surprisingly enough, what they discovered was that the bats are capable of changing how their wings move in order to maximize the force generated by flapping, effectively increasing the area of their wingspan by as much as thirty percent while flapping downward. Similarly, while flapping up, their wingspan decreases, in order to minimize drag.
"It distorts its wing shape and size continuously during flapping," Tafti explained.
"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," added co-author Kamal Viswanath, a research engineer at the United States Naval Research Lab's Laboratory for Computational Physics and Fluid Dynamics. Additionally, the researchers are looking to examine how the different wing motions actually impact the force the bat produces in flight.
"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?" continued Tafti. "And finally, how can we use this knowledge to control the flight of an autonomous flying vehicle?"
The full study can be found here, in the February 18 edition of the Journal Physics of Fluids.