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The Rise Of Insect Drones

Five years ago, Richard Guiler and Tom Vaneck were sitting at a bar a few blocks from their office, trying to take their minds off work. For nearly a year, the two engineers had been struggling to develop a durable drone that could dodge objects, navigate inside buildings, and fly in stormy weather. They’d tried fixed-wing models, but adding enough sensors to effectively detect obstacles made them too heavy to fly. They’d tried helicopters, but the rotors kept getting tangled in branches and electrical wires. They’d even built a motorized balloon; all it took was a gentle gust of wind to blow it off course.

As they sat nursing their beers, Guiler and Vaneck watched as a fly appeared to slam into a window. Instead of breaking apart on contact as their drones did, the insect bounced off the glass and recovered. Then it did it again. 

It was an epiphany, says Vaneck, who works for the Massachusetts research and development company Physical Sciences Inc. (PSI). We realized if we could make a manmade system that could hit things, recover, and continue on, that’s a revolution.

The idea of borrowing designs from nature is far from new, particularly when it comes to flight. The ancient Greeks dreamed up Daedalus, who fashioned wings for his son (which unfortunately worked a little too well). Leonardo da Vinci sketched a human-powered ornithopter. But until recently, inventors lacked the aerodynamics expertise to turn diagrams into mechanical versions of something as quotidian as a fly or a bee. As technology has advanced, scientists have decoded many of nature’s secrets. And engineers have developed the first flying, insect-inspired vehicles, opening the door to an entirely new class of machine: the microdrone.

“Nature has a several-hundred-million-year lead time on us when it comes to great design,” says Peter Singer, a fellow at the Washington, D.C.–based Brookings Institution. “The robots you know tomorrow are going to look like nothing you know today. More likely, they will look like the animals around you.”

Unraveling The Mystery Of Flight

Although insects and their relatives represent roughly 80 percent of the world’s animal species—some 900,000 known types—the mechanics of their flight had long been an enigma. Traditional fixed-wing aircraft rely on a steady flow of air over the wings. The same is true of helicopters and rotors. But as the wings of insects flap back and forth, the air around them is constantly changing. And the stubby wings of bees and other insects lift far more weight than can be explained using conventional steady-state aerodynamics principles.

Before scientists could understand flapping flight, they first had to see it in the minutest of detail. In the 1970s, Torkel Weis-Fogh, a Danish zoologist at the University of Cambridge, used high-speed photography to analyze the exact wing motions of hovering insects and compare them to the insects’ morphological features. From this, he formulated a general theory of insect flight, which included what he called the “clap-and-fling effect.” When insect wings clap together and then peel apart between the up and down strokes, the motion flings air away and creates a low-pressure pocket. Air then rushes back into the pocket, forming a swirling vortex. This vortex creates the force necessary to lift the insect between wing flaps. Similar vortices might be generated by the angle and rotation of the wings, Weis-Fogh posited, providing additional lift. 

Two decades later, computational techniques caught up with theory, and scientists began to apply these principles to manmade systems. Charles Ellington, a Cambridge zoologist and former Weis-Fogh student, built a robotic wing that could precisely mimic the movements of a hawk moth. He placed it in a wind tunnel filled with smoke so that as it flapped, he could analyze the fluid dynamics. At the University of California at Berkeley, neurobiologist Michael Dickinson built a robotic fruit-fly wing that likewise mimicked a fly’s natural motion, and he submerged it in a two-ton tank of mineral oil. Working independently, the researchers
characterized the aerodynamics of flight with unprecedented specificity.

Dickinson and electrical engineer Ron Fearing won a $2.5-million DARPA grant in 1998 to apply these principles to a fly-size robot. They assigned a graduate student named Rob Wood, among others, to help develop techniques to fabricate the tiny parts and painstakingly assemble them with a pair of tweezers. Dickinson and Fearing also communicated which aerodynamics insights the students should try to reproduce. “Flies have really complex wing trajectories. There are a whole bunch of subtle things that happen,” Wood says. “Michael told us the most important features to generate vortices and other aerodynamic effects.”

By the time Wood graduated in 2004 and opened his own lab at Harvard University, he had helped pioneer a way to use extremely energy-efficient, exotic materials to replicate the motion of a fly’s wing; he had built a gyroscope that could mimic the sensors insects use to detect body rotation; and he had invented methods to manufacture complicated systems on a miniature scale. What remained was to put it all together into a working insect-size flying machine.

Turning Insights Into Robots

On a freezing day in 2006, Wood arrived at his Oxford Street laboratory at Harvard. On the workbench sat a 60-milligram robot with a three-centimeter wingspan and a thorax roughly the size of a housefly. It was tethered to a six-foot-tall computer rack crammed full of high-voltage amplifiers and data-acquisition equipment. Wood carefully checked the connections and signals.

Then he flipped on the power and watched as the wings of his tiny creation began to vibrate, lifting the robot into the air for several seconds. Wood jumped in jubilation. It had taken him seven years to get to this point, and it would take another five to reach his next breakthrough: sustained flight along a preprogrammed path. An e-mail with proof of that milestone arrived in his inbox at 3 a.m. in the summer of 2012. An ecstatic graduate student had sent a video update on the lab’s latest prototype, now named RoboBee. It showed the delicate machine rising into the air and demonstrating, for the first time, stable hovering and controlled flight maneuvers in an insect-scale vehicle.

“I didn’t end up sleeping the rest of that night,” Wood says. “The next morning, we had champagne and all that, but it was more of a relief. If we couldn’t do this, we would have realized we were doing something wrong the whole time.”

Wood has pioneered microscale robotic flight; other researchers have used flapping-wing dynamics to reduce the size of aerial vehicles capable of carrying payloads. In 2011, California-based AeroVironment demoed its Nano Hummingbird. The aircraft has a 16.5-centimeter wingspan; it can fly vertically and horizontally and hover in place against gusting wind. It weighs 19 grams—lighter than some AA batteries—but it carries a camera, communications systems, and an energy source.

By Adam Piore.
This article originally appeared in the January 2014 issue of Popular Science.
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