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ROBOT EXOSKELETONS
by Tom Carroll
Arobotic exoskeleton utilizes an external shell of appendages to
support and move mass. Sometimes
called walking machines, wearable
robots, or robot suits, these devices
serve to augment physical capabilities
to either assist or protect a person
from certain conditions. The key factor
of this device is that it provides physical
capabilities in excess of its human
operator. We think of exoskeletons as
being a fairly new technology when,
in fact, they are several years old. For
example, insects and crabs have lived
quite happily with an external shell
structure with internal muscles to
move the different shell parts.
Robots are built with this same
type of construction — an internal
moving structure with an external
shell for aesthetics and/or to hide the
internal mechanisms and wiring.
These days, experimenters look to
exoskeleton technology to assist
humans in everything from daily living
and simple walking, to
lifting and carrying very
heavy loads.
over uneven terrain. However,
imagining what such a device can do
and then actually designing and
building one is quite different — as
many companies, universities, and
experimenters have found out. Just
having an exoskeleton balance in
place without falling is a major
accomplishment, not to mention
walking or carrying a heavy load.
a compressed air cylinder driving
pneumatic cylinders acting as
‘muscles.’ Lifesuit 15 can stand and
balance itself without a person
attached. Monty and his crew are
looking at future Lifesuits that use
biosynthetic muscle fibers and
lightweight batteries for power.
Power Requirements
Monty Reed’s Lifesuit
76 SERVO 11.2009
What’s In a
Design?
Just what is required
to design and build an
exoskeleton to augment
the capabilities of a
human? The military for
example, has long been
interested in exoskeleton
‘suits’ to allow soldiers to
carry heavy loads quickly
One might think that building an
exoskeleton to allow a disabled person
to walk would be easy, but that
design goal has proven quite difficult
to achieve by many groups. One
person who has worked diligently to
acheive success in this area is Monty
Reed. He has been working on a
robotic exoskeleton to assist persons
who have difficulty walking or who
are unable to walk due to an injury or
disease. Monty’s “They Shall Walk”
research program is
based in the Seattle
area. He is presently
developing Lifesuit
15 and 16 and has
appeared on several
national news and
scientific shows.
Prototype 14 shown
in Figure 1 weighs
about 75 pounds and
allows the wearer
to walk up to about
2. 5 miles per hour, and
ascend and descend
stairs. It is powered by
FIGURE 1. Monty Reed
and his Lifesuit.
Speaking of that, delivering
power to a human-sized exoskeleton
suit has always been one of the
biggest challenges for developers. Just
as human-size humanoid robots have
exhibited short ‘battery life’ due to
the large motors required, an
exoskeleton designed for a human
must use large motors or pneumatic
cylinders to move appendages with
even the smallest loads.
Developers of these suits have
long discarded lead-acid and nickel-cadmium batteries in favor of the
newer lithium and NiMH technologies
which provide far greater power
density per pound. Even pneumatic
systems require substantial battery
power to drive control systems.
Some of us will remember the
“Six Million Dollar Man” from the 70s.
Though Steve Austin had a partial
robotic endoskeleton and not an
exoskeleton, Austin nonetheless
required a unique power system to
run 60 miles per hour and jump over
20 foot walls.
Of course, he was ‘nuclear
powered,’ but that is far beyond what
was available in the 70s, and even
