A News Health Technology — 05 December 2014

Robot-Control-Theory-ProstheticThe University of Texas at Dallas has reported results of a study in which the application of new and existing theorums to a prosthetic leg resulted in a robotic prosthetic leg that closely mimics the natural gait of human walking.

The study addressed some of the shortcomings of prosthetic legs.  In an article by LaKisha Ladson, of UT Dallas, Dr. Robert Gregg said, “The gait cycle is a complicated phenomenon with lots of joints and muscles working together.” Dr. Gregg  is a faculty member in the Erik Jonsson School of Engineering and Computer Science and lead author of the paper.

While a person constantly monitors and adapts to changes while walking, such as changes in terrain and speed, prosthetic legs are unable to do so. Current prostheses can only be tuned to work in one or two modes that best meet different needs for the user.  This results in a prosthetic leg with a less stable and unnatural gate than a human limb.

According to the study, Gregg applied Robot Control theory, Metro-Adusing gait cycle models of recent bipedal robots combined with a “human-inspired invariance property called effective shape” to adapt the model to human conditions such as the momentary stance periods, and changing terrain and speeds encountered when walking.

Utilizing advances such as Robot Control theory, prostheses can function much more naturally than today’s prosthetic legs, constantly shifting modes and fine-tuning as necessary, quickly enough to result in a natural human-like gait.

“Our approach unified multiple modes of operation into one and resulted in technology that could help people in the future,” he said.

Subjects in the study were able to perform on a treadmill, at varying speed levels equivalent to a fast-walking able-bodied person.

“We did not tell the prosthesis that the treadmill speed was increasing. The prosthesis responded naturally just as the biological leg would do,” said Gregg.

The study included researchers from the Rehabilitation Institute of Chicago, Northwestern University and the University of New Brunswick; and was funded by the United States Army Medical Research Acquisition Activity, the Burroughs Wellcome Fund and the National Institutes of Health through the National Institute of Child Health and Human Development.

 Video courtesy of University of Texas at Dallas, Bionic Locomotion YouTube page.

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Geoff Sims

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