OPTIMIZED SYSTEMS

Bionic Man Says: Better than Original

R. Colin Johnson | Date: 02-06-12 | Comments

The teenage fisherman who made national headlines when a shark attacked him in shallow water back in 2005, now claims his new smart prosthetic leg is better than the original.

A smart prosthetic leg from Vanderbilt University reacts like the real thing, according to its first recipient, Craig Hutto whose real leg was damaged beyond repair in a shark attack. Now Hutto says his biggest problem is getting his real leg to hustle enough to keep up with the smart prosthetic limb.

In shorts, Hutto�s bionic leg is obvious, but with long pants the natural gate enabled by its smart algorithms makes him indistinguishable from other pedestrians.

After a shark attacked Hutto during a trip to the Gulf Coast in Florida, the 16 year old fisherman�s life was saved by three nurses whose heroic efforts saved him from bleeding to death. Unfortunately, he lost his leg in the process. Hutto feared he would never walk again, but today he is walking tall on a smart bionic leg that his pioneering efforts helped make a reality. Now Hutto is studying to become a nurse like those who saved his life.

The key to Hutto�s change of fortune is the lightweight design and lifelike algorithms built into his smart prosthetic leg designed by Vanderbilt University mechanical engineer, Michael Goldfarb. The smart prosthetic reacts to the cues of walking like a real person, thanks to algorithms designed to mimic how people walk by anticipating the next step.

Two years ago, Goldfarb invited Hutto to become a test pilot for his smart prosthetic project, whose original mechanical design was funded by the National Science Foundation (NSF) and whose latest iteration--including the smart bionic algorithms--was funded by the National Institute of Biomedical Imaging and Bioengineering, at the National Institutes of Health (NIH).

Unlike traditional prosthetics which restrict motion, Goldfarb�s computer-controlled joints enjoy a range of motion comparable to that of real legs. The battery powered motors--one driving the knee joint and one driving the ankle joint--respond to signals from the computer which is tracking their motion with micro-electro-mechanical system (MEMS) sensors.

The team of Goldfarb, Hutto, and Brian Lawson, another Vanderbilt mechanical engineer, worked together to make the prosthetic leg�s programming responsive to cues given to it by the wearer. As a result, the prosthetic achieves the bionic moniker by virtue of the life-like algorithms instilled into it which infer what the wearer is trying to do.

For example, a �climbing stairs� action is triggered in the bionic leg by a backward kick gesture which signals the computer to switch to the stair-climbing algorithms that lifts its knee joint high enough that the foot clears the lower step landing on the higher one.

Hutto claims it takes less effort to walk with the prosthetic leg than his real leg, because once triggered, the smart prosthetic takes over, powering the leg through its range of motion without any further effort from Hutto. As a consequence, he has to hustle with his real leg to keep up.

To help Hutto keep up, Goldfarb's team has intentionally programmed delays into the leg's motion algorithms, so that the wearer can synergistically stay in perfect step.

Goldfarb�s group recently licensed their technology to an undisclosed prosthetic manufacturer who is currently building commercial prototypes which it will test market next year.