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Meet
the Robots: Ariel, Rhex, Sprawl, and Mecho-Gecko
The
PolyPEDAL Lab's research into the motion of many-legged
creatures has inspired significant advances in robotics.
Collaborating with numerous faculty from other UC Berkeley
departments and universities around the country, Full
has helped build robots that are faster, more stable,
more maneuverable and far less complicated than the
machines of the past.
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VIDEO:
Watch Ariel go for a swim.
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Crab-like
Ariel heads into the surf. All robot photos on this page
©2000 Peter
Menzel, from Robo
sapiens: Evolution of a New Species
(MIT Press) |
Ariel
Moving
just like a crab, this autonomous robot built by iRobot (formerly
IS Robotics) is the first legged platform capable of walking
either on land or underwater in the turbulent surf zone. Ariel's
streamlined body shape and leg design minimize drag. Able
to climb over obstacles and crevices that would block traditional
wheeled vehicles, the robot also can resist the impact of
waves. Ariel is also completely invertible — if flipped
over by the waves, its legs simply reorient so that the "top"
of the body becomes the bottom. In addition to insight into
leg design (minimizing the degrees of freedom to simplify
control), stance width and actuator placement, Full's research
illuminated useful behaviors such as "pitching"
(changing the angle of attack for negative lift), grasping,
burrowing, climbing and righting. Ariel is funded by the Defense
Advanced Research Projects Agency (DARPA) and the Office of
Naval Research. Ariel has been outfitted with a new brain
and sensors. It is undergoing tests in which it locates mines
in the surf zone.
VIDEO: RHex takes a walk.
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Above,
former University of Michigan graduate student Ulu Saranli
puts an early version of RHex through its paces over an
obstacle course.
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RHex
The
Robot Hexapod, RHex (pronounced "rex") for short,
is the most maneuverable robot ever built. A collaboration
by Daniel Kodistchek of the University of Michigan, Martin
Buehler at Canada's McGill University and Full, the latest
version of RHex is about as big as a shoebox. It can bump
along at up to 3 meters per second and last close to two hours
on one battery charge.
With
its snub-nosed, squat form and dogged persistence over rocks
and obstacles, RHex resembles a hyperactive terrier, but in
locomotion it's closer to a cockroach. It has six legs oriented
in the horizontal plane, like those of crabs, lizards and
cockroaches; each leg turns clockwise around its central axis,
giving it purchase even on uneven steps.
"Basically,
it has six springy legs and six motors, and that's it,"
says Full. "It may look different from a cockroach, because
we didn't copy it, but the critical principles have transferred
completely." RHex has self-correcting reflexes —
"preflexes," Full calls them — like springs
and shock absorbers that help it overcome obstacles. The robot
simply bounces along, whirling legs finding a purchase on
uneven surfaces. Full and the other researchers are in discussions
with the Jet Propulsion Lab about sending RHex on the 2007
mission to Mars, where legged robots will be needed to navigate
the rough terrain.
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VIDEO:
Sprawlita can bounce over anything.
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Stanford
engineer Mark Cutkosky (left) and students Sean Bailey
and Jorge Cham with Sprawlita.
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Sprawl
The
SPRAWL family of six-legged robots — developed by Stanford
University's Center for Design Research in conjunction with
Full — represents a leap forward in robotic materials.
Using a new engineering technique called shape deposition
manufacturing, the researchers can not only form limbs in
the right shape, but also build desired material properties
(like stiffness or bendability at certain points) right into
them.
Sprawlita's
entire body is manufactured as one piece: servomotors and
wiring are embedded in the body's plastic, while the servo
attachment, compliant hip joint and pneumatic piston are all
embedded in the same plastic leg "unit." SPRAWL
is modeled on the cockroach; its piston-driven legs act as
springs, bouncing over any object in its path without requiring
feedback from the environment. The latest version of SPRAWL
can reach speeds of up to five body-lengths per second and
is very close to matching the force pattern exerted by a running
cockroach.
Mecho-Gecko
While
Full and Berkeley engineering professor Ron Fearing study
geckos' setae, the tiny hairs on its feet, for clues to replicating
nature's miraculous dry adhesive, iRobot has built two gecko-inspired
robots with Full's help. The Mecho-Gecko's three legs are
tipped with a pressure-sensitive adhesive (think Post-Its)
to mimic the unroll-and-peel-off manner in which geckos climb,
while the Bull-Gecko uses the same adhesive on bulldozer-like
treads instead of legs. The next design will be a legged version
with a flexible spine.
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