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A ROBOT that can both walk and swim has been simulated in California.
Understanding the complex behaviour involved in switching from trotting to
swimming could lead to a new generation of amphibious robots, say
researchers.

Auke Ijspeert and Michael Arbib of the Brain Simulation Laboratory at the
University of Southern California in Los Angeles wanted to investigate how
behaviour emerges from simple signals in a creature鈥檚 central nervous system. So
they built a computer simulation of a salamander鈥檚 central nervous system, and
superimposed it on a computer animation.

The resulting 鈥渟alamander鈥� exists in a simulated world of flat ground and
water. Gravity pulls it down, frictional forces act on its feet as it walks, and
swirling inertial forces affect it when it is swimming. 鈥淏eing able to explore
by crawling in and out of the sea is not a trivial problem,鈥� says John Hallam of
the artificial intelligence department at the University of Edinburgh. 鈥淭here is
a tremendous niche market for amphibious robots which could be used for
navigation and exploration.鈥�

Moving from water to land, or vice versa, is a tough problem for a robot,
because it has to completely change its gait and adapt to the new environment,
without stopping. Robotic designers have traditionally tried to solve this by
breaking down the problem into parts and solving them individually. But this
approach is too inflexible, says Ijspeert.

Animals deal with this problem by using sensory inputs as switches that turn
different neural control mechanisms on or off. These in turn are transformed
into complex and coordinated movements in the body. Through studying
salamanders, Ijspeert and Arbib were able to test various ideas about how
different neural mechanisms worked鈥攁nd see how vertebrates control their
bodies.

By copying natural oscillators in the brain that produce rhythmic signals for
various types of movement, the researchers were able to produce quite complex
behaviours. 鈥淭he circuits are capable of generating trotting and swimming
gaits,鈥� says Ijspeert. As the robot 鈥渟ees鈥� water approaching, or feels it, a
series of neurological switches make it change from the trotting oscillator to
the undulating swimming oscillator.

According to Ijspeert, the salamander was an ideal choice because it has many
similarities with humans, but on a simpler scale. 鈥淚t鈥檚 a living fossil of one
of the first vertebrates that made the transition onto land,鈥� he says. He
believes his research will help us learn more about our own control mechanisms.