Robot bat wing gives flight insights

US researchers say they've built a robotic bat wing that will allow them to learn more about how the real thing works in nature. Scientists at Brown University say they want to know more about how bat wings work because the strong, flapping flight of bats offers great possibilities for the design of small aircraft, among other applications. The researchers report their robot version has allowed them to uncovered many flight secrets of real bats: the function of ligaments, the elasticity of skin, the structural support of musculature, skeletal flexibility, upstroke and downstroke. The robot, mimicking the wing shape and motion of the lesser dog-faced fruit bat, has been tested in a wind tunnel and has provided data that could never be collected directly from live animals, they said. "We can't ask a bat to flap at a frequency of eight hertz then raise it to nine hertz so we can see what difference that makes," graduate student Joseph Bahlman said. "They don't really cooperate that way." The model, on the other hand, can do exactly what the researchers want it to do. They can control each of its movement capabilities individually, they said, adjusting one parameter while keeping the rest constant to isolate the effects. "We can answer questions like, 'Does increasing wing beat frequency improve lift and what's the energetic cost of doing that?'" Bahlman said. "We can directly measure the relationship between these kinematic parameters, aerodynamic forces, and energetics." While the robot can't match the complexity of a real bat's wing, which has 25 joints and 34 degrees of freedom, it has provided valuable data, he said. "We learned a lot about how bats work from trying to duplicate them and having things go wrong," he said.