Simple guidelines keep machines hauling and placing bricks
Courtesy of Eliza Grinnell/Harvard School of Engineering and Applied Sciences
Human construction crews, meet RoboTermites. Like the mound-building insects, these squat little robots can erect complicated structures without an instruction manual.
Using just a few preprogrammed rules, some traffic laws and a stack of foam bricks, the bots get busy building towers, pyramids and fortresslike walls, Harvard computer scientist Justin Werfel and colleagues report in the Feb. 14 Science.
One day, such robotic builders might be able to take on risky human jobs, such as building sandbag levees during floods. And like a termite or ant colony that gets stepped on, Werfel says, “it doesn’t matter if some of the robots are lost — the rest will keep going.”
Termites are architects of the insect world. The itty bitty animals paste together dirt and chewed-up bits of wood to build mansion-style mounds, with open chimneys and labyrinths of snaking tunnels.
But perhaps most impressive, Werfel says, is the fact that termites can build at all. “It’s frankly amazing,” he says. “There’s no central brain assigning them tasks, no one coordinating what they do.” Instead, millions of insects working side by side each decide their next moves for themselves(SN: 5/9/09, p.16).
Werfel and colleagues created computer programs that let robot construction crews act like independent insects. One program converted a building’s blueprints into “traffic laws” for roaming robots to follow. The laws told the robots where they could travel at any spot within the construction site, a checkerboard-like grid.
Another program gave the bots some basic guidelines to prevent gridlock: Always cruise counterclockwise around the structure, for example, and lay bricks one after another along a row, instead of skipping around. With these rules and traffic laws, the builder bots could construct complicated structures without a plan of action and without knowing what the other robots were up to.
Each machine, about the size of a tissue box, scoops up square bricks one-by-one with a forklift-style arm. As the bots haul bricks through the construction site, they use infrared sensors on their bellies to detect navigation cues. Lines on the ground tell the bots where to start, and crosses on the bricks help the little builders figure out their location.
Scientists have created multirobot building teams before but relied on navigational aids similar to GPS to track the robots’ positions. Werfel’s team’s robots navigate on their own, says Vijay Kumar, a robotics engineer at the University of Pennsylvania in Philadelphia, who has assembled swarms of robot helicopters. “That’s a lot more complicated,” he says.
Stéphane Magnenat, a robotics researcher at ETH Zürich, is impressed that termite-inspired programming of robots could function in real life. “That’s what makes this work great,” he says. “It’s not easy to combine everything and have it actually work.”
CONSTRUCTION CREW With just a few simple rules and a stack of foam bricks, a construction team of little robots can erect complicated structures, such as pyramids and fortresslike walls. But instead of using a detailed plan of action, the bots rely on basic building instructions and some traffic laws for getting around the construction site. Credit: J. Werfel et. al/Science 2014; Harvard University; adapted by Ashley Yeager
J. Werfel, K. Petersen and R. Nagpal. Designing collective behavior in a termite-inspired robot construction team. Science. Vol. 343, February 14, 2014, p. 754. doi:10.1126/science.1245842.