Washington, April 2
In a world's first,
researchers from Carnegie Mellon University and North Carolina State
University have developed an unpowered ankle exoskeleton that reduces
the metabolic cost of walking by approximately seven percent - thus
helping individuals walk using less energy.
The results are
roughly the equivalent of taking off a 10-pound backpack and are
equivalent to savings from exoskeletons that use electrically-powered
devices.
The device is the result of eight years of patient and
incremental work, mapped out on a whiteboard by Steve Collins and Greg
Sawicki when they were graduate students together at the University of
Michigan in 2007.
"Walking is more complicated than you might
think. Everyone knows how to walk but you do not actually know how you
walk," said Collins, assistant professor of mechanical engineering at
Carnegie Mellon in a paper that appeared in the journal Nature.
For
the innovation, the team performed careful analyses of the biomechanics
of human walking and then designing a simple, ultra-light-weight device
that relieved the calf muscle of its efforts when it was not doing any
productive work.
The calf muscle exerts energy not only when
propelling the body forward, but also when it performs a clutch-like
action, holding the Achilles tendon taut.
With this insight in
mind, the team created an ankle exoskeleton that offloads some of the
clutching muscle forces of the calf, reducing the overall metabolic
rate.
A mechanical clutch engages when the foot is on the ground
and disengages when the foot is in the air, to avoid interfering with
toe clearance.
This clutch takes over the effort of the calf,
producing force without using consuming any energy and thereby reducing
the overall metabolic rate.
Over several years and many iterative
designs, the team developed a carbon-fiber design that is ultra-light,
yet rugged and functional.
The entire device weighs approximately one pound per leg or less than a work boot.
According
to experts, the device is a triumph of elegance, simplicity and
bio-specific interventions over complex, over-engineered designs.
"It
is a real exciting milestone for the field of assistive devices. They
have taken an assistive device and lowered the cost of human walking,"
reacted Thomas Roberts, expert in the biomechanics of locomotion from
Brown University.
One of the long-term goals of Collins and
Sawicki's project is to use lightweight, energy-efficient exoskeletons
to assist individuals with mobility issues.
In the future, the
team intends to test the current device with individuals who have a
variety of mobility issues to determine what designs might work best for
different populations.
They are also interested in developing
exoskeleton components for the knee and the hip, where they believe they
may be able to garner even larger benefits.
