RoboticsCockroaches gait informs search-and-rescue robot design

Published 25 February 2013

More than 70 percent of Earth’s land surface is not navigable by wheeled or tracked vehicles, so legged robots could potentially bridge the gap for ground-based operations like search and rescue and defense. New insights on how cockroaches stabilize could help engineers design steadier robots for operating on difficult terrain.

Running cockroaches start to recover from being shoved sideways before their dawdling nervous system kicks in to tell their legs what to do, researchers have found. These new insights on how biological systems stabilize could one day help engineers design steadier robots and improve doctors’ understanding of human gait abnormalities.

In experiments, the roaches were able to maintain their footing mechanically — using their momentum and the spring-like architecture of their legs, rather than neurologically, relying on impulses sent from their central nervous system to their muscles.

The response time we observed is more than three times longer than you’d expect,” said Shai Revzen, an assistant professor of electrical engineering and computer science, as well as ecology and evolutionary biology, at the University of Michigan. Revzen is the lead author of a paper on the findings published online in Biological Cybernetics. It will appear in a forthcoming print edition.

What we see is that the animals’ nervous system is working at a substantial delay,” he said. “It could potentially act a lot sooner, within about a thirtieth of a second, but instead, it kicks in after about a step and a half or two steps — about a tenth of a second. For some reason, the nervous system is waiting and seeing how it shapes out.”

A University of Michigan release reportsthat to arrive at their findings, the researchers sent fifteen cockroaches (one-by-one, in forty-one trials) running across a small bridge onto a placemat-sized cart on wheels. The cart was attached to an elastic cord that was pulled tight like a loaded slingshot and held in place with a strong magnet on the other side. Once a roach was about a body length onto the cart, the researchers released the magnet, sending the cart hurling sideways.

The force was equivalent to a sumo wrestler hitting a jogger with a flying tackle, said Revzen, adding that cockroaches are much more stable than humans.

To gather detailed information about the roaches’ gait, the researchers utilized a technique Revzen developed several years ago called kinematic phase analysis. It involves using a high-speed camera to constantly measure the position of each of the insects’ six feet as well as the ends of its body. A computer program then merges the continuous data from all these points into an accurate estimate of where the roach is in its gait cycle at all times. The approach gives scientists a more

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