US researchers say they have built a robotic bat with life-like wing flaps, offering possibilities for the design of small aircraft.
Brown University researchers uncovered the flight secrets of real bats: the function of ligaments, the elasticity of skin, the structural support of musculature, skeletal flexibility, upstroke, downstroke.
The robot, which mimics the wing shape and motion of the lesser dog-faced fruit bat, is designed to flap while attached to a force transducer in a wind tunnel.
As the lifelike wing flaps, the force transducer records the aerodynamic forces generated by the moving wing. By measuring the power output of the three servo motors that control the robot's seven movable joints, researchers can evaluate the energy required to execute wing movements.
Testing showed the robot can match the basic flight parameters of bats, producing enough thrust to overcome drag and enough lift to carry the weight of the model species.
The work was done in labs of Brown professors Kenneth Breuer and Sharon Swartz, who are the senior study authors.
The faux flapper generates data that could never be collected directly from live animals, said Joseph Bahlman, a graduate student at Brown who led the project.
Bats cannot fly when connected to instruments that record aerodynamic forces directly, so that isn't an option - and bats don't take requests.
"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. They don't really cooperate that way," Bahlman said.
But the model does exactly what the researchers want it to do. They can control each of its movement capabilities - kinematic parameters - individually. That way they can adjust 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 in a statement.
"We can directly measure the relationship between these kinematic parameters, aerodynamic forces, and energetics," he said.
