- Artificial muscles that should give space
robots animal-like flexibility and manipulation ability will get their
first test on a small NASA rover destined to explore an asteroid.
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- Under development by Dr. Yoseph Bar-Cohen
of NASA's Jet Propulsion Laboratory, Pasadena, CA, the artificial muscles
are based on a simple, lightweight strip of highly flexible plastic that
bends and functions similarly to human fingers when electrical voltage
is applied to it.
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- Bar-Cohen and a small team of scientists
and engineers are working to turn these strips into grippers and strings
which can grab and lift loads, among many other potential uses. These
strips and strings, known as artificial muscles or electroactive polymers
(EAPs), have the potential to greatly simplify robotic spacecraft tasks.
The technology could lead in the future to the development of insect-like
robots that emulate biological creatures.
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- Years from now, these devices could also
conceivably replace damaged human muscles, leading to partially "bionic
men" and "bionic women" of the future, according to Bar-Cohen
and his fellow researchers. "My hope is someday to see a handicapped
person jogging to the grocery store using this technology," said Bar-Cohen,
leader of JPL's Nondestructive Evaluation and Advanced Actuator Technologies
unit, although such "blue sky" medical applications, even if
proven feasible, may be decades away.
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- In the near-term, two EAP actuators are
planned for use as miniature wipers to clear dust off the viewing windows
of optical and infrared science instruments on the Mu Space Engineering
Spacecraft (MUSES-CN) nanorover. This mission, led by the Japanese space
agency ISAS, is designed to land the palm-sized rover on an asteroid following
its 2002 launch, and return a sample of the asteroid to Earth.
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- "That's just the tip of the iceberg
when it comes to space applications," Bar-Cohen added. "Electroactive
polymers are changing the paradigm about the complexity of robots. In
the future, we see the potential to emulate the resilience and fracture
tolerance of biological muscles, enabling us to build simple robots that
dig and operate cooperatively like ants, soft-land like cats or traverse
long distances like a grasshopper."
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- Unlike human hands, which move by contracting
and relaxing muscles, typical robotic arms utilize gears, hydraulics and
other expensive, heavy, power-hungry parts. In future planetary exploration
missions, where robots will need to perform tasks like collecting and manipulating
samples of soil or ice, such mass and complexity becomes a problem. To
meet these challenges, Bar-Cohen and his team have developed two types
of artificial muscles that respond quickly to small amounts of electricity
by lengthening or bending.
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- The first is a flexible polymer ribbon
constructed from chains of carbon, fluorine and oxygen molecules. When
an electric charge flows through the ribbon, charged particles in the polymer
get pushed or pulled on the ribbon's two sides, depending on the polarity.
The net result: The ribbon bends. Using four such ribbons, Bar-Cohen
has fashioned a gripper that can pick up a rock.
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- The second consists of thin sheets wrapped
into cigar-like cylinders that stretch when one side of a sheet is given
a positive charge and the other a negative charge. These charges cause
the wrapped sheet to contract toward the center of the cylinder, and this
constriction forces the cylinder to expand lengthwise. When the power
supply is turned off, the cylinder relaxes, enabling it to lift or drop
loads.
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- Eight individual researchers or groups
from around the world will demonstrate their work on artificial muscles
as part of the Society of Photo-Optical Instrumentation Engineers' (SPIE)
6th Annual International Symposium on Smart Structures and Materials in
Newport Beach, CA, in early March, with a media session planned for the
evening of March 2. Contact Pat Wright of the SPIE (360/676-3290, x609)
for further information on this event.
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- Further information about Bar-Cohen's
research and related activities is available at: http://ndeaa.jpl.nasa.gov
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- A three-page fact sheet on the MUSES-CN
rover is available at: http://www.jpl.nasa.gov/facts/muses.pdf
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