This nifty flying robot can hover, bank, and turn as deftly as a fruit fly

Ars Technica » Scientific Method 2018-09-13

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Enlarge / The Delfly Nimble robot hovers in front of its creator, Matej Karasek of Delft University Technology. (credit: Henri Werij, TU Delft)

Flying insects like bees, dragonflies, and fruit flies can perform impressive aerodynamic feats, particularly when seeking to evade predators or the swatting motion of a human hand. Now Dutch scientists have built a flying robot capable of executing similar maneuvers—despite being much larger than the average insects—that could shed light on how these creatures achieve those feats. The scientists described their work in a new paper in Science.

There was a time when scientists believed that insect wings worked a lot like airplane wings. The up and down motion of their wings would generate lift because air flowing over the wing follows its slightly tilted surface, while the downward flow lowers the air pressure above the wing, lifting it just enough to keep the body aloft. (This is a simplified, and therefore incomplete, explanation for the complicated aerodynamics of airplane lift based on Bernoulli's principle, but it will suffice for the purposes of this post.) But in the 1990s, a zoologist named Charles Ellington decided to test this theory by putting various insects in actual wind tunnels. The conventional lift they measured simply wasn't sufficient to account for their ability to fly.

Ellington's subsequent research showed that a stable leading-edge vortex is the most likely explanation for how insects stay aloft. Once the vortex forms, it spirals out along the wing toward the tip, drawing air outward so as to avoid a stall. That explains how insects generate lift to hover, but not how they manage to execute complicated maneuvers like making rapid banked turns. That's possibly due to how an insect wing can rotate to slightly get rid of the vortex for an extra bit of lift, enabling the insect to change direction. But there is still plenty of mystery remaining for scientists to explore. And that's where this new flying robot comes in.

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