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Caterpillar robot's recoil too quick to see

Tufts University creates a silicone caterpillar, GoQBot, that can curl into a wheel to escape danger.

Video screenshot by Tim Hornyak/CNET

Ever notice how some caterpillars can recoil violently when bothered? Researchers at Tufts University are intrigued by this behavior, and have built a lightning-fast robot that replicates it.

GoQBot, described in a study in the journal Bioinspiraton & Biomimetics, emulates the "ballistic rolling" escape tactic employed by some Crambidae caterpillars. The bugs curl into a wheel when threatened and leap to safety.

The recoil happens within 100 milliseconds, which the Tufts researchers led by Huai-Ti Lin, describe as "one of the fastest self-propelled wheeling behaviors in nature."

Exactly how the caterpillars achieve this is a bit of a mystery. GoQBot is a 4-inch-long, soft-bodied robot devised to understand the forces at play. When it jumps, as seen in the video below, it goes through roughly 1G of acceleration and over 200 rpm of angular velocity, as measured by a force plate under the robot.

GoQBot is made of silicone rubber which flexes when the embedded shape memory alloy coils trigger the rolling action (see another vid here). It has five infrared emitters on its side so the researchers can see how it moves with a 3D motion-tracking system.

In the study, the researchers state that caterpillars don't use ballistic rolling more often because it requires a lot of power, and the results are unpredictable, as seen when the bug thrashes around in midair.

Still, ballistic rolling might be a useful technique for limbless rescue robots working in disaster zones. It would allow them to both crawl into small spaces and travel quickly when necessary, something snake-like robots can't do very well.

"Due to the increased speed and range, limbless crawling robots with ballistic rolling capability could be deployed more generally at a disaster site such as a tsunami aftermath," Lin said in a release. "The robot can wheel to a debris field and wiggle into the danger for us."

That's a neat concept, but having seen the aftermath of the March 11 tsunami in northern Japan, I think GoQBot would have to be impervious to jagged debris, water, and mud to do an effective job. But the faster it could move, the faster it could find victims.