Researchers have found that fruit flies can rapidly compensate for catastrophic wing damage, maintaining their previous stability after losing up to 40% of the wing. This finding could help in the design of versatile robots that face a similar challenge of quickly adapting to failures in the field.
The Penn State-led team released its results today (November 18) at the Achievements of science.
To conduct the experiment, the researchers changed the wing length of anesthetized fruit flies, simulating the trauma that flying insects can suffer. They then hung the flies on a virtual reality ring. To mimic what flies see in flight, the researchers played virtual images on tiny screens inside the ring, making the flies move as if they were flying.
“We found that flies compensate for their injuries by flapping the damaged wing harder and reducing the speed of the healthy wing,” said corresponding author Jean-Michel Mangeau, associate professor of mechanical engineering at Penn State. “They achieve this by modulating signals in their nervous system, which allows them to fine-tune their flight even after injury.”
By flapping the damaged wing harder, fruit flies trade off some performance, which is only slightly reduced, to maintain stability by actively increasing damping.
“When you’re driving on a paved road, there’s friction between the tires and the surface, and the car is stable,” Mangeau said, comparing cushioning to friction. “But on an icy road, the friction between the road and the tires is reduced, which causes instability. In this case, the fruit fly, as a driver, actively increases damping with its nervous system in an attempt to increase stability.’
Co-author Bo Cheng, Penn State’s Kenneth K. and Olivia J., associate professor of mechanical engineering. Kuo noted early in his career that stability was more important than power for flight performance.
“When a wing is damaged, both performance and stability are usually impaired; however, flies use an ‘internal handle’ that increases damping to maintain the desired stability, even if this results in further reduced performance,” Cheng said. “In fact, it has been shown that it is stability, not the required power, that limits the maneuverability of flies.”
The researchers’ work suggests that fruit flies, with only 200,000 neurons compared to 100 billion in humans, use a complex, flexible movement control system that allows them to adapt and survive injury.
“The complexity of the flies we discovered here is unmatched by any existing engineered system; the complexity of the fly is more complex than that of existing flying robots,” Mangeau said. “We’re still a long way from engineering to replicate what we see in nature, and this is another example of how far we have to go.”
In an increasingly complex environment, engineers are challenged to develop robots that can quickly adapt to malfunctions and accidents.
“Flying insects may inspire the design of flying robots and drones that can intelligently respond to physical damage and maintain performance,” said co-author Wael Salem, a PhD candidate in mechanical engineering at Penn State. “For example, designing a drone that can compensate for a faulty engine in flight, or a robot with legs that can lean on other legs when one of them gives way.”
To study the mechanism by which flies compensate for wing damage during flight, collaborators at the University of Colorado Boulder created a robotic prototype of a mechanical wing similar in size and function to that of a fruit fly. The researchers carved out a mechanical wing, replicating the Penn State experiments, and tested the interaction between the wings and the air.
“With only a mathematical model, we need to make simplifying assumptions about the wing structure, wing motion, and wing-air interactions to make our calculations comfortable,” said co-author Kaushik Jayaram, associate professor of mechanical engineering. at the University of Colorado Boulder. “But with a physical model, our prototype robot interacts with the natural world just like a fly, obeying the laws of physics. Thus, this installation captures the subtleties of the complex interaction between the wing and the air, which we do not yet fully understand. “
In addition to Mongeau, Cheng, Salem and Jayaram, co-authors include Benjamin Cellini, Penn State Department of Mechanical Engineering; and Heiko Kabutz and Hari Krishna Hari Prasad, University of Colorado Boulder.
The Air Force Office of Scientific Research and the Alfred P. Sloan Research Fellowship supported this work.