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Robert Full

VIDEO: Robert Full describes what's different about these robots.

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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.

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)


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.


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.

VIDEO: Sprawlita can bounce over anything.
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Stanford engineer Mark Cutkosky (left) and students Sean Bailey and Jorge Cham with Sprawlita.


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.

VIDEO: Mecho-Gecko won't be outrunning real lizards — yet.

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The Mecho-Gecko from iRobot, with the lizard that inspired its clinging method.


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.