Baltimore—Imagine a computer mouse that pushes back against your fingers, providing tactile prompts to guide you through complex programs; more precise and flexible robotic joints that use fewer parts; or conveyor systems that move objects not only forward, but also in other directions. That's just a short list of potential applications for a new spherical motor design that achieves a much wider range of motion than any of its predecessors.
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Rather than rotate on a single axis as conventional motors do, this spherical motor uses 80 permanent magnets and 16 circular electromagnets to achieve omnidirectional motion.
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According to inventor Gregory S. Chirikjian, associate professor in the department of mechanical engineering at Johns Hopkins University, the idea of a spherical motor isn't new. "But this is the first to achieve such a great range of motion," he says.
The device resembles a baseball resting on the rim of an open soup can, only much larger. The ball is the rotor, or rotating part of the motor. The top half of the ball is exposed, and the bottom half nests in the fixed part of the motor, or stator.
Johns Hopkins graduate student David Stein helped Chirikjian build the motor. To make the motor prototype, the team split a 1-ft diameter plastic globe in half. After gluing permanent magnets at precise positions inside, they put it back together to form the rotor. The concave stator assembly contains a hemispherical array of computer-controlled electromagnets.
Moving the ball is one thing, it's another to know its precise orientation once you've done so. Edward Scheinerman, chairman of the mathematical sciences department at the university, developed the orientation measuring technique of the globe on a National Science Foundation grant.
For more information, e-mail prs@jhu.edu or call (410) 516-7127.
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