BETTER BALANCE FOR BOTS
Trips and stumbles too often lead to falls for amputees using leg prosthetics, but a robotic leg prosthesis being
developed at Carnegie Mellon University promises to help
users recover their balance by using techniques based on
the way human legs are controlled.
Hartmut Geyer, assistant professor of Robotics, said a
control strategy devised by studying human reflexes and
other neuromuscular control systems has shown promise
in simulation and in laboratory testing, producing stable
walking gaits over uneven terrain and better recovery
from trips and shoves.
Over the next three years as part of a $900,000
National Robotics Initiative study funded through the
National Science Foundation, this technology will be
further developed and tested using volunteers with above-the-knee amputations.
Joining Geyer on the research team are Steve Collins,
associate professor of Mechanical Engineering and
Robotics, and Santiago Munoz, a certified prosthetist
orthotist and instructor in the Department of
Rehabilitation Science and Technology at the University of
“Powered prostheses can help compensate for
missing leg muscles, but if amputees are afraid of falling
down, they won’t use them,” Geyer said. “Today’s
prosthetics try to mimic natural leg motion, yet they
can’t respond like a healthy human leg would to trips,
Those principles might aid not only leg prostheses,
but also legged robots. Geyer’s latest findings applying the
neuromuscular control scheme to prosthetic legs and —
in simulation — to full-size walking robots, were
presented recently at the IEEE International Conference
on Intelligent Robots and Systems in Hamburg, Germany.
Geyer has studied the dynamics of legged walking and
motor control for the past decade. Among his
observations is the role of the leg extensor muscles,which
generally work to straighten joints. He says the force
feedback from these muscles automatically responds to
ground disturbances, quickly slowing leg movement or
extending the leg further as necessary.
The researchers found that the neuromuscular
control method can reproduce normal walking patterns
and that it effectively responds to disturbances as the leg
begins to swing forward as well as late in the swing. More
work will be necessary, he noted, because the control
scheme doesn’t yet respond effectively to disturbances at
More than a million Americans have had a leg
amputation and that number is expected to quadruple by
2050, Geyer said. About half of the amputee population
reports a fear of falling, and large numbers say the inability
to walk on uneven terrain limits their quality of life.
As witnessed at the DARPA Robotics Challenge Finals, walking isn’t easy for robots. However, the Chinese robot Xingzhe No.1 recently
walked for 54 hours straight, taking 360,000 steps that covered 83.28
miles, setting the world record for furthest distance walked by a
It did this all on a single charge. In fact, it could have walked even
further had the battery not died.
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