Self-organizing robots: Robotic construction crew needs no foreman (w/ video)

Feb 13, 2014
The TERMES robots can carry bricks, build staircases, and climb them to add bricks to a structure, following low-level rules to independently complete a construction project. Credit: Eliza Grinnell, Harvard SEAS

On the plains of Namibia, millions of tiny termites are building a mound of soil—an 8-foot-tall "lung" for their underground nest. During a year of construction, many termites will live and die, wind and rain will erode the structure, and yet the colony's life-sustaining project will continue.

Inspired by the termites' resilience and collective intelligence, a team of computer scientists and engineers at the Harvard School of Engineering and Applied Sciences (SEAS) and the Wyss Institute for Biologically Inspired Engineering at Harvard University has created an autonomous robotic construction crew. The system needs no supervisor, no eye in the sky, and no communication: just simple robots—any number of robots—that cooperate by modifying their environment.

Harvard's TERMES system demonstrates that collective systems of robots can build complex, three-dimensional structures without the need for any central command or prescribed roles. The results of the four-year project were presented this week at the AAAS 2014 Annual Meeting and published in the February 14 issue of Science.

The TERMES robots can build towers, castles, and pyramids out of foam bricks, autonomously building themselves staircases to reach the higher levels and adding bricks wherever they are needed. In the future, similar robots could lay sandbags in advance of a flood, or perform simple construction tasks on Mars.

"The key inspiration we took from termites is the idea that you can do something really complicated as a group, without a supervisor, and secondly that you can do it without everybody discussing explicitly what's going on, but just by modifying the environment," says principal investigator Radhika Nagpal, Fred Kavli Professor of Computer Science at Harvard SEAS. She is also a core faculty member at the Wyss Institute, where she co-leads the Bioinspired Robotics platform.

This video is not supported by your browser at this time.
Hardware demonstration of three robots building a branching structure (see Figure 4B for more information). Multiple different paths along the structure exist for the robots to follow from entry to exits. The total elapsed time in this clip is 31 minutes. Credit: Science/AAAS

Most human construction projects today are performed by trained workers in a hierarchical organization, explains lead author Justin Werfel, a staff scientist in bioinspired robotics at the Wyss Institute and a former SEAS postdoctoral fellow.

"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," he says. "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."

This video is not supported by your browser at this time.
Hardware demonstration of three robots working on a castle-like structure, starting from a partially complete state (see Figure 4A for more information). Robots are autonomous, independently controlled, and have strictly onboard, short-range sensing. The total elapsed time in this clip is 23 minutes. Credit: Science/AAAS

Instead, termites rely on a concept known as stigmergy, a kind of implicit communication: they observe each others' changes to the environment and act accordingly. That is what Nagpal's team has designed the robots to do, with impressive results. Supplementary videos published with the Science paper show the robots cooperating to build several kinds of structures and even recovering from unexpected changes to the structures during construction.

Each executes its building process in parallel with others, but without knowing who else is working at the same time. If one robot breaks, or has to leave, it does not affect the others. This also means that the same instructions can be executed by five robots or five hundred. The TERMES system is an important proof of concept for scalable, distributed artificial intelligence.

The TERMES robots can build themselves staircases to reach the next construction points, and they know how to add bricks that advance construction without blocking important paths. Credit: Eliza Grinnell, Harvard SEAS

Nagpal's Self-Organizing Systems Research Group specializes in distributed algorithms that allow very large groups of robots to act as a colony. Close connections between Harvard's computer scientists, electrical engineers, and biologists are key to her team's success. They created a swarm of friendly Kilobots a few years ago and are contributing artificial intelligence expertise to the ongoing RoboBees project, in collaboration with Harvard faculty members Robert J. Wood and Gu-Yeon Wei.

"When many agents get together—whether they're termites, bees, or robots—often some interesting, higher-level behavior emerges that you wouldn't predict from looking at the components by themselves," says Werfel. "Broadly speaking, we're interested in connecting what happens at the low level, with individual agent rules, to these emergent outcomes."

Harvard graduate student Kirstin Petersen and staff scientist Justin Werfel admire a termite mound in Namibia. Credit: Self-Organizing Systems Research Group, Harvard SEAS

Coauthor Kirstin Petersen, a graduate student at Harvard SEAS with a fellowship from the Wyss Institute, spearheaded the design and construction of the TERMES robots and bricks. These robots can perform all the necessary tasks—carrying blocks, climbing the structure, attaching the blocks, and so on—with only four simple types of sensors and three actuators.

"We co-designed robots and bricks in an effort to make the system as minimalist and reliable as possible," Petersen says. "Not only does this help to make the system more robust; it also greatly simplifies the amount of computing required of the onboard processor. The idea is not just to reduce the number of small-scale errors, but more so to detect and correct them before they propagate into errors that can be fatal to the entire system."

In contrast to the TERMES system, 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. These approaches can improve group efficiency and help the system recover from problems quickly, 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.

"It may be that in the end you want something in between the centralized and the decentralized system—but we've proven the extreme end of the scale: that it could be just like the termites," says Nagpal. "And from the termites' point of view, it's working out great."

Explore further: Programming smart molecules: Machine-learning algorithms could make chemical reactions intelligent

More information: "Designing Collective Behavior in a Termite-Inspired Robot Construction Team," by J. Werfel et al. Science, 2014.

Related Stories

Kilobots bring us one step closer to a robot swarm

Jun 17, 2011

(PhysOrg.com) -- When you think about robots, the odds are that you think about something that is fairly large. Maybe you picture a robot arms bolted to the floor of a factory or if you are feeling particularly ...

Robots learn from each other on 'Wiki for robots'

Jan 13, 2014

Now it's not just people – robots are also connected by internet thanks to RoboEarth. Next week, after four years of research, scientists at Eindhoven University of Technology (TU/e), Philips and four other ...

Recommended for you

FIXD tells car drivers via smartphone what is wrong

13 hours ago

A key source of anxiety while driving solo, when even a bothersome back-seat driver's comments would have made you listen: the "check engine" light is on but you do not feel, smell or see anything wrong. ...

Watching others play video games is the new spectator sport

19 hours ago

As the UK's largest gaming festival, Insomnia, wrapped up its latest event on August 25, I watched a short piece of BBC Breakfast news reporting from the festival. The reporter and some of the interviewees appeared baff ...

User comments : 5

Adjust slider to filter visible comments by rank

Display comments: newest first

grondilu
4 / 5 (1) Feb 13, 2014
Could this algorithm be used with the cubic robots that were developed lately? You know, those that move and jump with a reaction wheel?
antialias_physorg
4 / 5 (1) Feb 14, 2014
Could this algorithm be used with the cubic robots that were developed lately? You know, those that move and jump with a reaction wheel?


Sure, but they'd be very inefficient at moving bricks around (if they land on the bricks that might not be a good idea, either)

Using these cubes as building blocks themselves would be neat, but a terrible waste of electronics, magnets, batteries, ... )

The robots they show are neat, but it would be hard for them to build upwards unless a LOT of extra space was available for stairways.

For any kind of building (whether it be planar or highrise) I think these gizmos are the future:
http://www.youtub...Z3UnnS_0
SiBorg
4 / 5 (1) Feb 14, 2014
It's a fascinating proof of concept for emergent behaviour that is just as applicable to a quadcopter as it is to the bots they've demonstrated with. I can imagine this is going to be of a lot of use to any autonomous platform where the need for mobility is putting real constraints on the amount of processing power that can be carried about.
bearly
not rated yet Feb 14, 2014
I hope they figure out how to infect congress with this algorithm.
mosahlah
not rated yet Feb 15, 2014
This would be a critical capability for autonomous land combat systems, parcularly in a non-permissive electronic environment. An unmanned vehicle will have to deal with combat much like a person. That means reacting individually to OCOKA, ACE status, fuel, and MET-TC. Simply advancing, shooting forward, and waiting for orders may work a few times, but once the enemy recognizes the capabilities of your system, they can overcome it rather easily, such as the Iranian countermeasure against US stealth drones a few years ago. If a system can self organize its own countermeasure, such as quickly filling a gap in observation, or defeating enemy IDF capacity, we will be within reach of reducing our own battlefield casualties to zero.