Fruit flies use corrective movements to maintain stability after injury

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

The Penn State-led team published their findings today (November 18) in Science Advances.

To conduct the experiment, the researchers altered the wing length of anesthetized fruit flies, mimicking an injury that flying insects can sustain. They then suspended the flies in a virtual reality ring. Mimicking what flies would see in flight, the researchers beamed virtual images onto tiny screens in the ring, making the flies move as if they were flying.

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

By beating 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, the 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 there is less friction between the road and the tyres, which causes instability. In this case, a fruit fly, as 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.

“Under wing damage, performance and stability would generally suffer; however, the flies use an ‘inner knob’ that increases damping to maintain the desired stability, even if this results in a further drop in performance,” said Cheng: “In fact, it has been shown that it is the stability, not the power requirement, that limits fly maneuverability.”

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 after injury.

“The complexity we’ve discovered here in flies is unmatched by any existing engineering systems; the sophistication of the fly is more complex than 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 adapt quickly 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 Penn State mechanical engineering PhD candidate. “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 in.”

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

“With a mathematical model alone, we have to make simplifying assumptions about wing structure, wing motion, and wing-air interactions to make our calculations tractable,” said co-author Kaushik Jayaram, professor mechanical engineering assistant. at the University of Colorado at Boulder. “But with a physical model, our prototype robot interacts with the natural world much like a fly would, subject to 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.