Robot Uses Lizard Tail to Leap

Science fiction often envisions worlds populated by humanoid robots. In reality, insects, reptiles and non-human animals often serve as a more practical template for automatons. The more legs a robot has, the more easily it can navigate tough terrain. Likewise, claws are less challenging to emulate than primate-esque hands and, as a team of researchers reports this week, tails are an incredibly versatile stabilizing mechanism.

The back-ends of snakes, ants or even grasshoppers have served as such an inspiration to some roboticists. Now, Robert Full, a biologist at the University of California, Berkeley, and his students have turned to the red-headed African Agama lizard. The researchers? work, published online Thursday in advance of publication in the January 12 issue of Nature, describes how a careful study of the Agama?s approach to leaping on slippery surfaces led to improvements in robotic design. (Scientific American is part of Nature Publishing Group.)

High-speed videography and motion capture revealed how an Agama raises its tail to counteract a lack of footing on slippery surfaces when vaulting from a flat, rectangular block to a vertical surface. When the block was covered with sandpaper, the lizard required less stabilization and its tail remained in a down position during a leap.

Full and his team applied the lizard?s tail-raising schemes to a small, robotic four-wheeled vehicle dubbed Tailbot. After attaching a stabilizing tail to the rear of the vehicle and sending it off a ramp, the researchers noted that Tailbot sank nose down with its tail in the down position. When the tail was raised to a reptile-replicating degree based upon the Tailbot?s attitude coming off the ramp, it was able to land on its wheels in a more balanced position.

Full and his students are now investigating the role of the tail in controlling roll?and pitch and yaw?while running. These are just the latest developments in Full?s full-on flirtations with robots. He has worked with engineers since the mid-1990s when he helped to develop the crab-inspired Ariel, a minesweeping robot made by iRobot Corp. (famous for its Roomba robotic vacuum) that can look for buried explosives in surf zones. In 2008 Full co-founded the Center for Integrative Biomechanics in Education & Research (CiBER) at University of California, Berkeley, to further integrate the work of biologists and engineers when designing technology.

Some of Full?s work is evident in Stickybot, a mechanical collaboration with Stanford in 2006 that could walk up smooth surfaces such as windows using an adhesive inspired by that the microscopic hairs found on the feet of geckos.

Other examples of so-called biomimetic machines include Boston Dynamics?s Legged Squad Support System, which resembles a headless pack mule, and a worm-like robot under development at Harvard University.

Image of a red-headed African Agama lizard swinging its tail upward to prevent forward pitching after a slip during take-off, courtesy of Robert Full lab/UC Berkeley

Video courtesy of Robert Full lab/UC Berkeley and Nature

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