Inspired by the collective intelligence of termites, researchers have created an autonomous robotic construction crew -- no supervisor, no communication, no advanced planning needed -- an important proof of concept for scalable, distributed artificial intelligence.
"Normally, at the beginning, you have a blueprint and a detailed plan of how to execute it, and the foreman goes out and directs his crew, supervising them as they do it," Harvard’s Justin Werfelsays in a press release. "In insect colonies, it’s not as if the queen is giving them all individual instructions. Each termite doesn’t know what the others are doing or what the current overall state of the mound is."
In Namibia, for example, millions of termites working for over a year have built an 8-foot-tall mound of soil -- a "lung" for their nest underground. Without a coordinated strategy, they rely on a kind of implicit communication called "stigmergy" -- observing each others’ changes to the environment and acting accordingly.
So Werfel and colleagues leveraged stigmergy to design algorithms that reflect termite behavior, and then implemented these algorithms in a set of construction robots. With their TERMES system, an assemblage of simple robots can build complex, 3D structures -- towers, castles, and pyramids -- without any central command, prescribed roles, or detailed plans. They just need the ability to sense a brick or bot nearby to make their next move.
Each robot in the construction team is equipped with just four sensors and three actuators. Here are the things TERMES robots can do:
Move forward, backward, and turn in place along a grid, while obeying predetermined traffic rules. "Traffic can only flow in one direction between any two adjacent sites, which keeps a flow of robots and material moving through the structure," Werfel explains.
Keep track of its own location with respect to the first "seed" brick.
Pick up a brick, carry it, and deposit it directly in front of itself. If it senses a brick in its path, it just takes it over to the next open space.
Detect other bricks and robots in the immediate vicinity. "Each is just reacting to what it encounters," Werfel explains.
Climb up or down a step the height of one brick.
Build themselves staircases out of foam bricks to reach the higher levels, adding bricks wherever they are needed.
Although each one follows just simple rules, together they exhibit intelligent behavior, doing "something really complicated as a group, without a supervisor," Harvard’s Radhika Nagpalsays, "without everybody discussing explicitly what’s going on." If one robot breaks, or has to leave, it doesn’t affect the others. Despite the loss (or not knowing about it), they keep working by following the cues of those robots that remain. This means the same instructions can be executed by five robots or 500. According to a Harvard press release:
It is currently more common for robotic systems to depend on a central controller. These systems typically rely on an “eye in the sky” that can see the whole process or on all of the robots being able to talk to each other frequently... but as the numbers of robots and the size of their territory increase, these systems become harder to operate. In dangerous or remote environments, a central controller presents a single failure point that could bring down the whole system.
In the future, these sorts of termite-inspired robots -- which are expendable and especially useful in places we might find "dirty, dangerous and dull," as Werfel says -- could lay sandbags before a flood and build shelters after an earthquake, and even perform simple construction tasks underwater or on Mars. "If you could send a team of robots to go build the habitat as the first step -- that's the really long-term vision," Werfel adds.
Here’s a nifty video of the termite robots at work:
Janet Fang has written for Nature, Discover and the Point Reyes Light. She is currently a lab technician at Lamont-Doherty Earth Observatory. She holds degrees from the University of California, Berkeley and Columbia University. She is based in New York.
Follow her on Twitter.