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DIGITAL PEOPLE

designed to replace a missing hand with one that looks real and copies natural motion and sensing abilities. This design also lends itself to bionic enhancements, as well as use in artificial beingsa prime example of the fruitful crossovers between medical applications and robotics.

Like Robonaut, the biomechatronic hand gives priority to the thumb and first two fingers, which move around an object and fit themselves to its shape to grasp it. The three digits are driven by electric motors and linkages tiny enough to be embedded in the palm and the fingers without making the hand look unnatural; however, the remaining two fingers are not motor-driven. Darios group has not yet built an entire hand, but they have made a prototype plastic finger, with two degrees of freedom corresponding to the two joints of a human finger. Despite the smallness of the motors in the artificial finger, the force it exerts as it bends is comparable to that from a real finger, and so the artificial hand seems capable of fine manipulation at least.

As far as its mechanical design goes, the biomechatronic hand in its present form could serve as a robotic appendage.But Darios project also includes efforts to link the mechanical device to the human ner- vous system to make an advanced prosthesis, and so enters the area of neurorobotics.As defined by John Chapin of the State University of New York and Karen Moxon of Drexel University,“ ‘neuroroboticsseeks to obtain motor command signals from the brain and transform them into electronic signals suitable for controlling a robotic device.Those commands could come from the cortex of the brain or from the peripheral nervous system.

The cortex is the thin, wrinkled layer of gray matterthat covers much of the brain. It performs higher intellectual functions and deals with sensory information, speech, and motor activities.The periph- eral nervous system is the part of the nerve network that carries out- side stimuli to the brain and returns appropriate responses.Even when a hand or limb has been amputated, the neural signals that once con- trolled the appendage are still generated in the cortex and sent to the appropriate nerves. The goal is to extract these neural pulses at the

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