Animal locomotion
as high science
Future robots will learn their moves from cockroaches, crabs and centipedes
By Robert
Sanders, Public Affairs
Posted May 10, 2000
At San Diego's Sea World, Rodger Kram videotapes penguins waddling across a force-measuring platform to rate the energy efficiency of their distinctive gait. Meanwhile, at Berkeley, Claire Farley tapes bright dots to the legs of students and videotapes them running across a similar platform to determine the relationship between muscle stiffness and springy legs.
Across campus, Robert Full tests cockroaches, crabs and centipedes to discover how springy legs provide stability, while down the hall, Steven Lehman stretches rabbit muscle fibers to find out how they work as brakes and springs as well as motors.
Michael Dickinson tracks blowflies in a test chamber to determine how feedback from their eyes affects the flight muscles and ultimately allows spectacular maneuverability. And Mimi Koehl builds foot-long models of lobster antennules to learn how these crustacean noses pluck odor molecules from the water swirling around them.
These half-dozen Berkeley professors in the Department of Integrative Biology comprise the largest and most diverse group in the country studying how animals -- including humans -- move.
What has emerged from the comparative biomechanics group and from their associates around the world are a set of principles that apply to animal locomotion of all kinds, whether it's running, swimming, flying or wriggling. As Koehl has found, these principles even apply to movement not associated with locomotion -- with sampling the environment, capturing food or just trying to stay put in the face of wind or water currents.
Last month, the Berkeley team summarized key findings from more than a decade of research at Berkeley and elsewhere in a review article titled "How animals move: an integrative approach," published in the journal Science.
Such principles are not merely academic. Full, Koehl and Dickinson, for example, regularly share information with engineers eager to learn the secrets of animals' amazing speed, control and mechanical stability so that they can adapt the principles to the design of robots. Lehman has found that his work on muscle fatigue is of interest to ergonomics specialists trying to deal with an epidemic of repetitive stress problems.
Kram, an assistant professor, recently hosted computer animators from Pixar Animation Studios to give them tips on creating more realistic animal movement for their next blockbuster movie. Full consulted with Pixar earlier on "A Bug's Life."
"In classic locomotion research, everyone focused on the force pushing an animal forward. Power and efficiency became central," said Dickinson. "That emphasis has really shifted, because the way animals execute motion is very, very complex and dynamic. Animals throw force out in all directions, seemingly out of control and not optimized for moving in one direction. We've found that these forces help produce stability and maneuverability."
One of the key recent findings in the field of biomechanics, Full added, is "that it's not how much power animals can produce, but how they stabilize and control themselves."
Full has demonstrated this with numerous creatures. He has shown that these animals run by bouncing along like pogo sticks with the same patterns seen in humans. The difference lies in the squat stance, where splayed, springy legs are superb in providing passive stability. This frees the brain to deal with navigation rather than tedious, instant-by-instant corrections at all the joints.
"The control is built into the structure, their sprawling stance," he said. "It's a self-stabilizing system that can simplify immensely how we think about animal motion, and help in the design of robots no one has seen before."
A major strength of the group is collaboration. This often emerges from weekly meetings where faculty, students and postdocs assemble to hear about new work and, as the seminar winds down, throw out silly ideas that often lead to great insight.
Kram noted how one student mentored by Koehl and Full used his findings on how humans move in reduced gravity -- he had suspended human volunteers from a harness while running -- to predict how crabs move underwater. When the student videotaped real crabs, she found the predictions to be amazingly accurate. These data led to the design of Ariel, the first legged amphibious robot.
Many of the principles discovered are now being co-opted by engineers to design robots. Dickinson is working with Berkeley engineer Ron Fearing to design a robotic fly, while Full is collaborating with various robotics labs to create robots that use principles employed by cockroaches, crabs and even geckos.
"With the invention of artificial muscles and novel techniques to manufacture flexible body parts," said Full, "we are on the verge of a revolution in biologically inspired robotics.
"Nature can now be a good teacher of engineers. But you don't want to copy, you want to extract principles," he said. "Nature has all kinds of screw-ups. Evolution is based on the principle of just good enough, it's not perfect at all. I think we can build robots today better than any one organism. We can do that now."
May 10 - June 6,
2000 (Volume 28, Number 33)
Copyright 2000, The Regents of the University of
California.
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