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Bioinspiration
Take design cues from the natural world.
By Martin C. Pedersen
August/September 2002
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Sprawlita
Engineered and Designed by Sean Bailey and Jonathan E. Clark Center for
Design Research, Stanford University
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SPRINGY LEGS
They push or bounce forward or backward (laterally as well)--a self-stabilizing
feature.
PREFLEXES (NOT REFLEXES)
Rather than wait for sensors, the legs' springs provide immediate feedback.
POSTURE
Sprawled legs provide stability.
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SIMPLE NERVOUS SYSTEM
The robot's internal feedback system operates as simply as a clock: movement
is its sole function.
LEG NUMBER AND GAIT
A six-legged configuration called the alternating tripod. The hind legs
are used for acceleration, the front ones are used mainly for deceleration;
the middle limbs perform both functions.
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Photo by Joe Budd
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At the Poly-PEDAL Laboratory, creatures like the cockroach, the crab, and
the gecko are placed--alive and skittering--under science's relentless gaze.
Using infrared light and high-speed video equipment, they're measured running
and climbing--clocked like thoroughbreds--all in the hope of answering questions
like, How does a cockroach achieve speeds of up to 50 body lengths per second?
And what can we learn from their extraordinary performance for practical
use?
One of the lab's major projects--done in collaboration with the Center for
Design Research at Stanford University--is a small (270 grams) six-legged
robot inspired by the cockroach. "Sprawlita," an early step in
the design of a fully autonomous robot, is being developed to do just one
thing--crawl. But by doing that it would solve two significant problems
currently plaguing the field: mobility and stability. "Think about
your conception of a robot--big, stiff, one motor, and a joint made of steel
with rotating parts," says director Robert Full, a biologist at the
University of California, Berkeley. "There's no animal in nature that
operates like that." In developing Sprawlita they rethought a basic
assumption about robot design, choosing legs over wheels or tracks. "The
use of legs is controversial because they're complicated and appear difficult
to control," Full says. "We thought if you simplified them,
then the legs could allow the robot to go anywhere."
Six-legged creatures have an arrangement called an alternating tripod that
is extremely stable and a model of efficiency. The hind legs are used
for acceleration, the front for deceleration, and the middle limbs perform
both functions. The cockroach's pliable legs push laterally too. Each set
works like a spring, bouncing from one side to the other. "By developing
this lateral leg spring in a robot, you can get incredibly stable behavior--a
robot that can negotiate very irregular terrain without a complex brain
or feedback," Full says. "In other words, the simplified
nervous system can act like a clock that sends out signals, tick, tick,
tick."
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MUSCLES
Because artificial muscle is years away, designers opted for pistons.
SENSE ORGANS
No eyes or antennae.
BRAIN
None. Only the robot's tuned skeleton computes.
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SKELETAL MATERIAL
No moulting. Insects shed their skins or shell, often dying in the process.
LONG ABDOMEN
Hinders mobility. The cockroach has learned to adapt.
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Photo by Corbis Images
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Some call the field biomimicry, but Full says mimicking nature
is a mistake. "You often hear the argument, 'Organisms have evolved
over millions of years, and they got it right,'" he says. "That's
only partly right, because evolution works on a just-good-enough principle.
Some evolved parts do well. Others don't. Instead we believe that you should
extract principles and concepts, and use them only when they're advantageous."
Bioinspiration--the term Full prefers--holds great potential for
humans: imagine quick, superstable robots capable of entering burning buildings,
or artificial muscle for prosthetic limbs. Its creative process, based
on an unlikely collaboration between biologists, mathematicians, and engineers,
is also particularly important. "We extract principles of how animals
move that allow us to build robots that nobody has built before."
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