Sunday, February 05, 2006


H.A.L (Hybrid Assistive Limb)

Two control systems interact to help the wearer stand, walk and climb stairs. A "bio-cybernic" system uses bioelectric sensors attached to the skin on the legs to monitor signals transmitted from the brain to the muscles. It can do this because when someone intends to stand or walk, the nerve signal to the muscles generates a detectable electric current on the skin's surface. These currents are picked up by the sensors and sent to the computer, which translates the nerve signals into signals of its own for controlling electric motors at the hips and knees of the exoskeleton. It takes a fraction of a second for the motors to respond accordingly, and in fact they respond fractionally faster to the original signal from the brain than the wearer's muscles do.

The motors respond faster to signals from the wearer's brain than their own muscles

While the bio-cybernic system moves individual elements of the exoskeleton, a second system provides autonomous robotic control of the motors to coordinate these movements and make a task easier overall, helping someone to walk, for instance. The system activates itself automatically once the user starts to move. The first time they walk, its sensors record posture and pattern of motion, and this information is stored in an onboard database for later use. When the user walks again, sensors alert the computer, which recognises the movement and regenerates the stored pattern to provide power-assisted movement. The actions of both systems can be calibrated according to a particular user's needs, for instance to give extra assistance to a weaker limb.


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