Kevin Fite has been working on the development of prosthetic limbs
for more than three years. Now with a $350,000 grant from the United States Army, Fite is ready to carry his research even further. In conjunction with the College of Nanoscale Science and Engineering’s Smart System Technology and Commercialization Center (STC), a Canandaigua, N.Y.-based company, Fite will be developing sensors that will enable prosthetic legs to better interface with the residual limb.
Legs are one of the hardest prosthetics to work on because of their inherent stature. To begin with, legs are fundamentally load-bearing structures. Also, because the prosthetic is under the patient’s body, sweat gathers there faster than in a prosthetic arm. These interface conditions introduce significant challenges to control the limb using external biosensors.
Fite, a mechanical engineering professor whose specialty is electromechanical systems, will be developing electromyogram (EMG) sensors and the computer programs that take the EMG signals and translate them into a reliable stream of information for moving the limb. An EMG is a small electrical sensor placed on the skin that can perceive the voltage changes attributed to muscle contraction. “It is a very noninvasive way to get neuromuscular commands from the user to the artificial limb,” Fite says. These sensors may also be useful in future exoskeletons, such as those being developed by Raytheon Sarcos, which augment the human body rather than replacing a part of it.
Fite’s research will tackle several problems: the actual command and control of the prosthesis, the algorithms to translate the electrical impulses into robotic movement, and ways of filtering extraneous signals from the sensors. For example, perspiration can provide false positives in EMGs, as well as cross signals. If the socket containing the sensors moves relative to the skin, the EMGs will be measuring incorrect signals, which could result in erratic movement by the prosthesis. “What we’re looking for is a good, clean, robust EMG signal in
the face of all these disturbances,” Fite says.
In the laboratory, several graduate students are aiding him in his research into prosthetic limbs, as will several undergrads who help out in the summer. STC will be manufacturing the sensors as Fite’s research progresses, as well as producing the sensors that monitor the condition of the prosthesis itself, all of which must be durable and flexible. Monitoring pressure, sheer and temperature are important to keeping the prosthesis in optimal working order.
The end goal for Fite’s research is to produce a powered leg prosthesis with output and appearance similar to that of an intact human leg and to demonstrate it to the Army. With the increasing frequency of improvised explosive devices (IEDs) in combat, and resulting amputations, the need for near-human prostheses is at an all-time high.