"Bionic" leg anticipates the wearer's moves
By Vincent Rice
October 24, 2011
It was not a good day for 16 year old Craig Hutto. On June 27, 2005, wading in crystal clear waters off a near-deserted beach 50 miles south of Panama City, Craig was attacked by an 8-foot bull shark and lost his right leg from above the knee. Today Hutto is a 6-foot 4-inch 23 year old studying Nursing at Middle Tennessee State. Fortunately for him, Nashville is also the home of Vanderbilt University where its Center for Intelligent Mechatronics has for seven years been developing an advanced prosthetic limb. They also happened to need a Lab Assistant to help them test it.
Professor Michael Goldfarb and his team are on the seventh iteration of a limb that combines a low weight (9lbs / 4 kg) aluminum alloy construction with embedded processors and powerful motorized knee and ankle joints. A rechargeable battery provides enough power for three days or 8 miles (14 km). A wide array of sensors monitor the leg's position and movement and the on-board software tries to anticipate the wearer's needs when sitting, standing, walking etc. A "stumble" routine for instance will try to lift the leg high to clear the obstacle and then plant it for stability. This anticipation means the leg operates much more like a real limb which allows the wearer to walk with a normal gait, even up and down stairs or across uneven terrain. See the video below.
"Going up and down slopes is one of the hardest things to do with a conventional leg," said Hutto. "So I have to be conscious of where I go because I can get very tired walking up and down slopes. But that won't be a problem with the powered leg because it goes up and down slopes almost like a natural leg."
Getting the Assistant position at Vanderbilt helped Hutto to pay his way through college but also allowed him to contribute to the development of an intelligent prosthetic limb that will greatly help many people that find themselves in his predicament.
"Craig deserves a lot of credit for his contributions to this," said Professor Goldfarb. "He tells us when there is something that is not going to work, or when there is some function that an amputee will not tolerate. We are always getting Craig to push it hard and see what needs to be better. When he really likes a behavior or there is something that surprises him, those are rewarding moments for us."
Freedom Innovations, a manufacturer of lower limb prosthetics. hopes to bring the licensed design to market soon at a price close to that of a standard passive device.
The Vanderbuilt University Center for Intelligent Mechatronics is also developing an anthropomorphic prosthetic arm project and an advanced exoskeleton to aid in physical therapy.