Human construction projects are generally
centrally planned, with people in leadership roles supervising how
everything is put together, and builders aware of the overall progress.
But termites and other
animals go about building in a different way, working independently.
Each termite reacts directly to what it encounters, rather than having a
preconceived notion of what to do. Collectively, the insects can create
a mound much larger than themselves.
"They do all of their coordination indirectly, by changing their shared environment," says Justin Werfel of the Wyss Institute for Biologically Inspired Engineering at Harvard University.
Werfel and colleagues
used this model of decentralized, reactive building to create robots
operating under those principles. Robots that behave this way could be
useful for construction projects that would be too dangerous for humans,
such as underwater research stations or in outer space. Another
possible application would be building levees out of sandbags in flood
zones, Werfel said.
"If you had a robot
system to handle that kind of building automatically, that would let you
keep people out of harm's way," Werfel said.
The findings are published in the journal Science and presented at the American Association for the Advancement of Science meeting this week.
These robots are small --
4.7 inches high, with a footprint of about 4 x 7 inches. The "bricks"
that they can manipulate, made of expanded urethane foam, are bigger
than these critters: 8.5 x 8.5 x 2 inches.
Researchers created
algorithms governing the behavior of the robots, so that they know what
to do when they encounter specific situations. It's not the blueprint
that guides the robots, but rather these predefined simple rules.
The construction begins with a single "seed" brick in a particular location.
The robots can move
forward, backward and turn in place. They were designed to be able to
climb up or down a step that is the height of one brick and build
staircases with the bricks to get themselves higher up.
Importantly, these
robots only detect bricks and other robots that are in their immediate
area; they have no idea how far along the overall structure is or what
more distant robots are doing.
"Robots obtain information about where bricks have been attached only through direct inspection," researchers wrote.
The design of the robots
in this research wasn't intended to be "cute," although they may appear
that way -- some researchers call them "frog-bots" or "squirrel-bots,"
said Kirsten Peterson, a co-author on the study. They have rounded
features for the sake of simplicity and using less material.
The robots have four
types of sensors, Peterson said. A pattern-recognition system, composed
of seven infrared sensors, can detect black and white patterns on the
bricks and helps with navigation.
In addition to tactile
sensing, the robots have a pattern recognition system, an accelerometer
to sense tilt, and five ultrasound sonar units to detect other robots
and help maintain distance from the perimeter of the structure.
To move around, the robots have wheel-legs called "whegs."
This study did not
optimize the robots for speed. It took three robots half an hour to
build a "trident" structure with eight blocks, Peterson said.
A decentralized system
of robots has some advantages over a centrally planned method of
building. If individuals perish, the plan doesn't fall apart, because it
doesn't depend on how many builders there are.
When everything is
planned out, you'd have to go back to the drawing board if some of the
robot builders bit the dust. But a decentralized system readily adapts
to the loss of participants, Werfel said, just like what happens in
nature with termites.
"If half the colony gets eaten by an aardvark, the rest can carry on," he said.
There are still some
engineering challenges that would need to be solved to ramp this up to
large-scale projects on Earth, the study said, but Werfel said it's
conceivable that designing robot systems such as these for disaster
zones would in the realm of years away, Werfel said.
For more extreme
environments such as other planets, scaling these kinds of robots up to
the task might take decades, Werfel said. But conceivably the principle
of this study could be applied to send robots to build a base on Mars.
If they build it, maybe we will come.
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