The findings could inform the design of fault-tolerant robots, the researchers say

Fruit flies can quickly compensate for catastrophic wing damage, researchers found, maintaining the same stability after losing up to 40% of a wing. This finding could inform the design of versatile robots, which face the similar challenge of quickly adapting to disasters in the field.

The Penn State-led team released its results today (November 18) at Scientific advances.

To conduct the experiment, the researchers changed the length of the wings of anesthetized fruit flies, mimicking an injury flying insects might suffer. They then suspended the flies in a virtual reality ring. Mimicking what the flies would see in flight, the researchers sent virtual images to tiny screens on the ring, making the flies move as if they were flying.

“We found that flies compensate for their injuries by beating the damaged arm harder and reducing the speed of the healthy arm,” said corresponding author Jean-Michel Mongeau, assistant professor of mechanical engineering at Penn State. “They achieve this by modulating signals in their nervous system, allowing them to adjust their flight even after injury. »

By flapping their damaged wing harder, fruit flies trade some performance – which decreases only slightly – to maintain stability by actively increasing damping.

“If you drive on a paved road, friction is maintained between the tires and the surface, and the car is stable,” Mongeau said, comparing damping to friction. “But on an icy road, the friction between the road and the tires is reduced, which causes instability. In this case, a fruit fly, like a driver, is actively increasing damping with its nervous system in an attempt to increase stability. »

Co-author Bo Cheng, Penn State Kenneth K. and Early Career Associate Professor of Mechanical Engineering Olivia J. Kuo noted that stability is more important than power for flight performance.

“In case of arm damage, performance and stability would generally suffer; however, the flies use an ‘internal knob’ that increases damping to maintain the desired stability, although this results in a further decrease in performance,” Cheng said. “In fact, it has been shown to be the stability, not the power requirement , that which 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 sophisticated and flexible motor control system, allowing them to adapt and survive injury.

“The complexity we’ve discovered here in flies is unmatched by any existing engineering system; the fly’s sophistication is more complex than that of existing flying robots,” Mongeau said. “We’re still a long way from the engineering side of trying to replicate what we see in nature, and this is just another example of how far we have to go . »

With increasingly complex environments, engineers are challenged to design robots that can quickly adapt to breakdowns or accidents.

“Flying insects can inspire the design of flying robots and drones that can intelligently respond to physical damage and maintain operations,” said co-author Wael Salem, a doctoral candidate in mechanical engineering at Penn State. “For example, designing a drone that can compensate for a broken motor in flight, or a legged robot that can rely on its other legs when you give up. »

To study the mechanism by which flies compensate for wing damage during flight, collaborators at the University of Colorado at Boulder created a prototype mechanical arm robot, similar in size and function to that of a fruit fly. The researchers cut the mechanical wing, repeating the experiments at Penn State and testing the interactions between the wings and the air.

“With only a mathematical model, we have to make simplifying assumptions about wing structure, wing motion and wing-air interactions to make our calculations feasible,” said co-author Kaushik Jayaram, assistant professor of mechanical engineering. . at the University of Colorado at Boulder. “But with a physical model, our prototype robot interacts with the natural world much like a fly, obeying the laws of physics. Thus, this configuration captures the intricacies of complex wing-air interactions that 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 at Boulder.

The Air Force Office of Scientific Research and the Alfred P. Sloan Fellowship supported this work.

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