[LINK] On termites as models for construction robots

[rfmcdonald]

Wired's Nadia Blake pointed towards the latest development in applied swarm intelligence.

Termites normally inspire thoughts of insect invasions, obnoxiously colored house-tents, or the Orkin man. But for a group of scientists at Harvard University, the cooperative insects inspired a whole new army of robots, described in Science.

These robots, each about the size of your head, follow a minimal set of rules when building a structure. Instead of detailed plans, they rely on environmental cues to accomplish their task — a minimalist strategy that’s based on a principle called “stigmergy.” Conceived in 1959 by a French biologist, the term describes how termite colonies cooperate and self-organize to build massive, intricate mounds. In some places, these mounds can be 8 feet tall; they’re also air-conditioned by a network of internal tunnels, and are often oriented along the Earth’s north-south magnetic axis.

But unlike humans, termites don’t follow blueprints or plans while constructing their homes. All they know is what the finished product is supposed to be, and what to pay attention to along the way. As each termite scoops up mudballs and deposits them in various places, it leaves a trail of chemical cues for other builders. Based on these cues, the other termites modify their building behaviors and deposit their own mudballs where the stuff is needed. Boom. Termite mound.

The fleet of Harvard robots follows this strategy, too. Their minimal programming includes the ability to move forward, backward, and rotate; they can also climb, sense, pick up and deposit bricks. Where they lay those bricks depends on what the other bots are doing and what the final structure is supposed to be.

Meeri Kim's Washington Post article goes into much more detail.

“Around here, you hear about termites destroying buildings,” said Justin Werfel, a Harvard University computer scientist and author of a study in the current issue of the journal Science. “But in Africa and Australia, they are known for building enormous, complicated mounds of soil.”

[. . .]

Each termite is an organism of fairly low complexity, but, using stigmergy, a colony can build a highly complex structure. So the team started with this simple framework: Each robot must have its own basic brain and sensors, and be programmed with certain “traffic rules” it must obey.

The sensors enable them to see bricks and robots next to them, and the traffic rules depend on the final structure. They prevent robots from placing bricks in places where they might easily collapse, or constructing a scenario in which a brick would have to be squished in between two others.

Each robot, about eight inches long, consists of internal metal gears and hardware as well as 3-D printed parts. The bricks themselves are also made in a way that helps the robots climb and align them better.

“In our system, each robot doesn’t know what others are doing or how many others there are — and it doesn’t matter,” Werfel said.

The main difference from the real-life insect is that termites don’t have a desired end product. Rather, there is a random component involved; given the same starting place, a colony will build a slightly different structure every time. But for constructing a house, for instance, the robots would need to follow a specific blueprint. So Werfel created the option for a user to input a picture of a predefined structure, and the robots will go to town on building it.

The paper in question is here.