A walking, swimming salamander comes alive, inside a computer
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's central nervous system. So they built a computer simulation of a salamander's central nervous system, and superimposed it on a computer animation.
The resulting "salamander" 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. "Being able to explore by crawling in and out of the sea is not a trivial problem," says John Hallam of the artificial intelligence department at the University of Edinburgh. "There is a tremendous niche market for amphibious robots which could be used for navigation and exploration."
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-and 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. "The circuits are capable of generating trotting and swimming gaits," says Ijspeert. As the robot "sees" 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. "It's a living fossil of one of the first vertebrates that made the transition onto land," he says. He believes his research will help us learn more about our own control mechanisms.
Author: Duncan Graham-Rowe
More at: http://rana.usc.edu:8376/~ijspeert/salamander.html
New Scientist issue: 23rd September 2000
PLEASE MENTION NEW SCIENTIST AS THE SOURCE OF THIS STORY AND, IF PUBLISHING ONLINE, PLEASE CARRY A HYPERLINK TO: http://www.newscientist.com