Getting small drones and other miniature craft to take flight has been fairly elementary work for designers in the past several years, but the really tricky parts--as any amateur drone pilot can tell you--have always involved the work of keeping those machines in the air and ensuring safe landings. Announced this week, however, a team of Harvard roboticists has taken a major step toward giving robots some of the flight advantages enjoyed by birds and bees--perhaps also paving the way for a truly terrifying, high-tech re-creation of Hitchcockian horror--by giving them the ability to perch.
Published in the latest issue of Science, the team's work demonstrates that their new microrobots or "RoboBees" are able to use static electricity to perch on leaves or similar services mid-flight in order to save energy. The study's first author Moritz Graule, who conducted the research with the Harvard Microbiotics Lab while studying at the School of Engineering and Applied Sciences (SEAS) and Wyss Institute for Biologically Inspired Engineering, explained in a press release,
Many applications for small drones require them to stay in the air for extended periods ... Unfortunately, smaller drones run out of energy quickly. We want to keep them aloft longer without requiring too much additional energy.
The team took inspiration from the countless flying birds and insects that perch to save energy during flight, which necessarily expends energy stores quickly. Co-author Kevin Ma noted, though, that translating animals' methods of sticking or clasping to high-up rest areas would involve complicated machinery and/or the kind of detaching force that is ultimately "inappropriate for a paperclip-[sized] microrobot."
Instead, the team outfitted the microbots with foam pads to protect them against the impact of landing on a chosen spot and harnessed static electricity as the means for getting robots to stick to their perches. That simple 'sticking' method takes advantage of the same principles that allow us to rub a balloon against wool and then attach it to the wall, make our little brother's hair stand straight up, or cause other low-impact, short-lived mischief: namely, the attraction of oppositely charged surfaces to one another.
“In the case of the balloon, however, the charges dissipate over time, and the balloon will eventually fall down,” Graule said. “In our system, a small amount of energy is constantly supplied to maintain the attraction.” That flow of energy comes from an electrode patch affixed to each RoboBee, which turns off to let bots release their grip on surfaces and which can keep them snugly attached to leaves, glass, and wood, among other things, when supplied with a charge.
Of course, the equipment that allows a bee-sized bot to rest under a leaf won't afford the same luxury to a meatier surveillance drone, but Ma explained that this innovative answer to the problem of how to let robots perch for a spell may impact future methods for perching and landing. “There are more challenges to making a robust, robotic landing system," he said, "but this experimental result demonstrates a very versatile solution to the problem of keeping flying microrobots operating longer without quickly draining power."
