One of the more challenging issues in the field of robotics is the development of stability. Whether a machine is on two legs, four legs, one wheel, or eight wheels, it isn’t easy to keep a body stable and viable when rolling over mountains, hills, creeks, discarded Chipotle burritos, and other humongous obstacles. To try to counteract these hurdles, scientists often try to develop better feedback systems that allow robots to respond instantaneously to changes in their terrain.
However, one of the most common and hardy critters on the planet is challenging this methodology. What if building inherent stability into the system is the most important component, and the computing system should only make changes on an incremental basis?
Meet the cockroach, that adorable lover of the insect world capable of remaining on-balance even with a severed head. In a recent experiment, researchers from the University of Michigan used a high-speed camera to constantly measure the position of each of the insects’ six feet as well as the ends of the body. They then set the cuddly critters on a doomed path.
The cockroaches crossed a bridge and landed on a wheeled cart attached to an elastic cord pulled taught by strong magnets. Once on said cart, the magnet was released, and the cart jerked sideways. In one of my favorite quotes of all-time from a researcher, the cockroach experienced forces, “equivalent to a sumo wrestler hitting a jogger with a flying tackle.”
Being much more stable than the common jogger, the cockroaches remained upright. But it wasn’t their brains that kept them so.
Based on the analysis of the motion of the insect’s legs and body, the central nervous system didn’t help make any adjustments for a period substantially longer than expected. It wasn’t that the brain was built for sloth, either; it’s that it chose not to send any commands until things played out for a bit. It adjusted the gait only at whole-step intervals rather that at any single point in a step.
The implications are that cockroaches use their momentum and the spring-like architecture of their legs to stay balanced rather than their brains.
“What we see is that the animals’ nervous system is working at a substantial delay,” said Shai Revzen, assistant professor of electrical engineering and computer science at the University of Michigan. “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.”
“The animals obviously have much better mechanical designs than anything we know how to build. But if we could learn how they do it, we might be able to reproduce it.”
The paper, “Instantaneous kinematic phase reflects neuromechanical response to lateral perturbations of running cockroaches,” was published in Biological Cybernetics by Revzen, as well as Samuel Burden, Talia Moore, Jean-Michael Mongeau, and Robert Full of the University of California – Berkeley.