Leaping Lizards!

Blog has been neglected. Sorry blog. In return, I give you a news story! I’m taking a science journalism course, and a recent assignment was to write a news story about a new scientific finding. So without further ado.


Leaping Lizards Inspire Jumping Robots
Researchers at the University of California Berkeley have built a tailed robot that can safely leap through the air using observations the scientists made about how tails stabilize the acrobatics of jumping lizards.

This achievement could lead to the development of highly mobile search-and-rescue robots in rough terrain where remaining upright is a crucial challenge, according to the researchers, who published their findings in Nature last month.

The most advanced walking robots today all have one thing in common: they fall over. “The most interesting aspect of robots is using them in places that people don’t want to go or can’t go,” said Tom Libby, the study’s primary author. “And some of these terrains are not able to be traversed by modern robots.” The goal, according to Libby, was to understand how millions of years of biology corrected the problem of something falling, and then to apply that understanding to an engineering design.

The Berkeley scientists first examined jumping lizards as they leaped off a small platform. The team encouraged the reptiles to run off a small platform similar to a gymnastic vault coated in a smooth slippery material. As they jumped, the lizards slipped on the surface and were forced off balance. Using a high-speed camera to capture the lizards’ motion, the scientists measured how their tail movements helped correct their slip during the leap.

The physics of this balancing act turns out to be related to how an object’s weight is distributed when it falls off balance. If there is more weight farther from the object’s center, it can be used to correct the imbalance. High-wire acrobats take advantage of this idea by using long flexible poles to maintain their balance. Small slips can easily be fixed by just a slight shift of the pole. Likewise, the researchers found that shifts in the position of the lizards’ tails help them maintain balance while jumping, even if they slipped on the slick vault during takeoff.

The key is flexibility. As the lizards were thrown off balance in one direction, they moved their tails in the opposite direction. By shifting their weight, the lizards remained upright and facing their intended landing zone. If the lizards had no tail, the scientists found through computer models, they would veer wildly off course after slipping since they could not correct their imbalance. The same computer models showed that a stiff, inflexible passive tail would help only slightly in keeping the jumpers upright. The ability to move their tails in response to slipping let the lizards stay consistently on target.

With this knowledge in hand, the scientists built a robot with a responsive tail to see if they could mimic the lizards’ airborne stability. In a setup similar to the slippery vault, the robots sped over a large ramp and into the air, where their stability could then be measured by a camera. The motor-controlled robot tails automatically responded to imbalance by mimicking the observed motion of the lizard tails. Like the lizards, the robots with tails were more capable of remaining upright in the air than robots without tails.

“This is a beautiful, simple experiment that many roboticists have wanted to try, so it was great to see it done,” commented Dr. Rod Grupen, professor of computer science at the University of Massachusetts Amherst and co-editor-in-chief of the Journal of Robotics and Autonomous Systems.

Surprisingly, the tailed robots were even more efficient than the lizards at correcting slip-ups. The reason, the scientists found, was that a tail with more of its weight located toward the tip is much better at correcting an unstable jumper. Such a finding has potentially important implications for the design of agile machines such as those needed in search-and-rescue operations or prosthetics for athletes.

While both Libby and Dr. Grupen agree that it will be long time before tailed robots find their way into everyday life, Dr. Grupen thinks the findings are immediately useful in general strategies for designing robots. “We’re getting more and more interesting robots, which is clearly the advantage of these experiments.”