Scientists and their students in a UC Berkeley lab have learned how African lizards use their tails to leap from predators - a discovery that allowed them to create a tiny robot with a tail that uses the same acrobatics for unprecedented maneuverability.
Similar robots could eventually be used, the scientists say, to search for bodies buried underneath earthquake rubble, or to land a spacecraft on low-gravity asteroids, or - as the Army suggests - to sneak inside buildings where enemy combatants lurk.
In today's edition of the journal Nature, UC Berkeley biologist Robert J. Full and Thomas Libby, his mechanical engineering graduate student, describe a series of experiments observing the leaping African rainbow lizards. The lizards swing their tails upright to balance themselves in midair and keep them from tumbling head over heels as they leap.
After detailed studies of the lizards' physiology, the team developed mathematical models of their tail motions. They used that information to build a movable tail for a four-wheeled, mini-robot that mimics the lizards' flights.
The inch-long robot, named "Tailbot," can take off from a ramp at a yard per second and land safely, tail-up, across a void several inches wide. Without the tail to balance and stabilize it, Tailbot crashed.
In Full's lab, biologists and engineers work together on how animal motions can be used to design robots with more useful legs or wheels.
"The science of robotics is just beginning," Full said. "We build our robots to behave the same way that our little animals, like crabs or geckos or cockroaches, have evolved to confront obstacles in their environment."
Full's lab also has created a six-legged robot named Ariel that mimics a crab's scuttle, allowing it to walk on sandy beaches, rock piles, underwater and in ocean surf.
Another six-legged robot named RHex moves with the persistence of a sniffing terrier, Full said, but is modeled after the way a cockroach speeds into the hidden cracks of a cupboard.
And then there's Mecho-Gecko, a robot whose three legs are tipped with pressure-sensitive adhesive, enabling it to climb vertical walls much the way geckos do.
Stanford robotics engineer Mark Cutkosky, who has worked with Full in the past, said the new report on leaping lizards and the Tailbot robot's performance "provides valuable insights for the next generation of mobile robots.
"In the past, robots haven't moved fast enough to take advantage of acrobatic maneuvers that involve dynamic effects such as rapidly rotating or flicking a tail, or rapidly rotating the limbs, as human jumpers or pole vaulters do."
But Full's report, Cutkosky said, "shows us how a tail and a flexible spine can be used to increase mobility and maneuverability at high speeds when robots can jump, spin and glide across the terrain."
There were also side benefits of the lizard research, Full said.
The models his team created confirmed a hypothesis about how swift dinosaurs moved - a theory developed more than 40 years ago by John Ostrom, a Yale paleontologist.
Ostrom studied the vicious racing and slashing theropods like deinonychus, and velociraptor, the evil co-star of the later movie "Jurassic Park."
Their leaping attacks, Full said, followed the "dynamic stabilizer" models of his team's research.
He said the movie appropriately captured how the velociraptor moved. Without knowing the mathematics of the leaping African lizards, the movie creators still "got it right!" Full said.
Full's team's research was supported by grants from the National Science Foundation and MAST, the U.S. Army's Micro Autonomous Systems Technologies Alliance.
