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WALTER REED AND ARIZONA STATE CREATE PROSTHESIS
OF THE FUTURE -- Researchers are teaming up to
create
the next generation of powered prosthetic
devices
based on lightweight energy storing springs.
Story here...
http://www.poly.asu.edu/
news/2007/04/30/
Story below:
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ASU, Walter Reed researchers create prosthesis
of the future
MESA, Ariz. — Researchers at Arizona State University’s Polytechnic
campus and the Military Amputee Research Program at Walter Reed Army
Medical Center are teaming up to create the next generation of powered
prosthetic devices based on lightweight energy storing springs.
The device, nicknamed SPARKy, short for Spring Ankle with Regenerative
Kinetics, will be the first-of-its-kind smart, active and energy-storing
transtibial or below-the-knee prosthesis.
Existing technology in prosthetic devices is largely passive and
requires the amputee to use 20 to 30 percent more energy to propel
themselves forward when walking compared to an able-bodied person,
according to Thomas Sugar, ASU assistant professor of engineering at the
Polytechnic campus.
Once complete, SPARKy is expected to provide functionality with enhanced
ankle motion and push-off power comparable to the gait of an able-bodied
individual.
“A gait cycle describes the natural motion of walking starting with the
heel strike of one foot and ending with the heel strike of the same
foot,” says Sugar. “The cycle can be split into two phases — stance and
swing. We are concerned with storing energy and releasing energy
(regenerative kinetics) in the stance phase.”
When you look at the mechanics of walking, it can be described as
catching a series of falls, explains Sugar. In the team’s device, a
tuned spring brakes falls and stores energy as the leg rolls over the
ankle during the stance phase, similar to the Achilles tendon.
Sugar’s team, made up of doctoral students Joseph Hitt and Matthew
Holgate, and Barrett Honors College student Ryan Bellman, have coined
SPARKy a robotic tendon because of its bionic properties.
“What we hope to create is a robotic tendon that actively stretches
springs when the ankle rolls over the foot, thus allowing the springs to
thrust or propel the artificial foot forward for the next step,” says
Sugar. “Because energy is stored, a lightweight motor can be used to
adjust the position of a uniquely tuned spring that provides most of the
power required for gait. Thus less energy is required from the
individual.”
The team is the first to apply regenerative kinetics to design a
lightweight prosthetic device. Others are using large motors combined
with harmonic drives, a monopropellant or extremely high pressure oil.
Sugar’s team already has proof that SPARKy is working. In recent
experiments with able-bodied subjects outfitted with a robotic ankle
orthosis, or a powered assist device, the researchers found that the
spring and motor combination was able to amplify the motor power by
three-fold. This significant finding allows SPARKy to be downsized from
a 6-7 kg motor system to a 1 kg (2 lb) system which is significant
weight savings for those who wear a prosthetic.
“We expect this device to revolutionize prosthetics and will be
especially helpful for military personnel wounded in active duty,” says
Hitt.
The project is a multi-phased effort led by ASU’s Human Machine
Integration Lab, Arise Prosthetics and Robotics Group, Inc. Arise
Prosthetics is helping in the fitting of the device and Robotics Group,
Inc. is designing embedded processors and motor amplifiers.
The first phase of SPARKy featuring the robotic tendon is expected to be
ready for demonstration in December 2007. “I will know it is successful
when a wounded solider is able to walk using the device on a treadmill,”
says Sugar about this phase.
The project will culminate with the functionality to support walking in
a daily environment, which is expected in 2009.
About Dr. Thomas Sugar
Dr. Thomas Sugar has built a large research program in medical robotics,
as a co-investigator on a National Institutes of Health (NIH) contract
for stroke rehabilitation, the principal investigator on an NIH grant on
robotic spring ankles for gait assistance, and principal investigator on
the three-year Department of Defense grant to build SPARKy.
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Larry Scott --
