A new type of robot balances on a ball rather than relying on legs or wheels.

The Ballbot, as it is called, can move in tight spots, making it potentially more useful than other designs for some uses.

Carnegie Mellon University robotics Professor and inventor Ralph Hollis first started fiddling with the thing at home. Then he got funding from the National Science Foundation.

"We wanted to create a robot that can maneuver easily and is tall enough to look you in the eye," Hollis said. "Ballbot is tall and skinny, with a much higher center of gravity than traditional wheeled robots. Because it is omnidirectional, it can move easily in any direction without having to turn first."

An onboard computer reads balance information from its internal sensors, activating rollers that mobilize the urethane-coated metal sphere on which it moves. At rest, Ballbot stands on three retractable legs.

Long-legged humanoid robots are complex, expensive, and so far don't work that well. Ballbot has challenges to overcome, too. It still needs arms and a head, for instance.

"We want to make Ballbot much faster, more dynamic and graceful," he said. "But there are many hurdles to overcome, like responding to unplanned contact with its surroundings, planning motion in cluttered spaces and safety issues."

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