With an actively controlled tail even robots can leap and remain upright

University of California, Berkeley, Scientists and students studied how lizards manage to leap successfully even when they slip and stumble, and found that swinging the tail upward is the key to preventing a forward pitch that could send them head-over-heels into a tree. The study is published in Nature today (Jan 5).

The scientists subsequently added a tail to a robotic car they named Tailbot and discovered that it's not as simple as throwing your tail in the air.

Robots and lizards have to adjust the angle of their tail just right to counteract the effect of the stumble. Given an actively controlled tail, even robots can make a leap and remain upright, according to a University of California, Berkeley press release.

“We showed for the first time that lizards swing their tail up or down to counteract the rotation of their body, keeping them stable,” said team leader Robert J. Full, UC Berkeley professor of integrative biology. “Inspiration from lizard tails will likely lead to far more agile search-and-rescue robots, as well as ones having greater capability to more rapidly detect chemical, biological or nuclear hazards.”

Full and his team used high-speed videography and motion capture to record how a red-headed African Agama lizard handled leaps from a platform with different degrees of traction, from slippery to easily gripped sandpaper.

They coaxed the lizards to run down a track, vault off an obstacle and land on a vertical surface with a shelter on top. When the friction on the obstacle was reduced, lizards slipped, potentially causing their body to spin out of control.

When the researchers saw how the lizard used its tail to counteract the spin, they created a mathematical model as well as Tailbot to better understand the animal's skills. With a tail but no feedback from sensors about body position, Tailbot took a nose dive when driven off a ramp, which mimicked a lizard's take-off. Tailbot was able to stabilize its body in midairwhen body attitude was sensed and fed back to the tail motor sent. The actively controlled tail redirected the angular momentum of the body into the swing of the tail, just as with leaping lizards, Full said.