Robots borrow tail design from jumping lizards
Tails used to stabilize and maintain balance during jumps
We can build it. We have the technology. Research into unmanned robotics has received ample attention lately. This is mostly due to the military’s increased use of drones to fight remotely without endangering human life. However, unmanned robots are also receiving attention from engineers who wish to use them not for waging war but for performing rescues in the aftermath of disasters. When the terrain is treacherous, the air is toxic or when hazardous chemicals pervade the environment, robots need to be able to navigate and do their job in the most effective way possible.
Researchers at the UC Berkeley Center for Interdisciplinary Bio-inspiration in Education and Research (CiBER) lab are working on a robotic design that uses a tail derived from lizards and dinosaurs to provide unsurpassed stability even when the robots lose their balance.
“Inspiration from lizards will likely lead to far more agile search-and-rescue robots,” said Robert Full, team leader and a professor of integrative biology at UC Berkeley.
The research team, consisting of graduate and undergraduate students in biology and engineering, has discovered that lizards use their tails as a counterbalance to prevent them from falling head-over-heels when they jump. The team added a tail to a robotic car called Tailbot and found that landing safely after losing balance is strongly dependant on the angle of the tail relative to the body.
The team used high-speed cameras to film lizards as they jumped.
“To see whether the lizards used their tails to stabilize themselves, we had them run down a track and jump up to a wall,” said Thomas Libby, an integrative biology graduate student and co-author of the study. “We used a slippery patch to make them slip during the jump and If they couldn’t stabilize themselves, they would crash headfirst into the wall.”
The researchers found that the lizards swung their tails up or down to keep their body perfectly oriented for an accurate landing. The swinging motion of the tail transfers angular momentum away from their body, which reduces rotation during jumps and fast movement.
“It’s analogous to how a human might swing their arms when they slip on ice, but lizards are much more effective at it because their tails are so large,” Libby said.
As Libby pointed out, directly copying a lizard’s tail for a mechanical design is a bad idea. The live lizard uses its tail for many functions that include maintaining balance, storing fat, communication and defense. The mechanical version will not have to satisfy all of these requirements. Their research shows that the tail from a velociraptor would have much more effective stabilizing properties, but there just is not enough data available to know if velociraptors had the same amount of tail articulation (range of motion) that the lizards do.
“The biological form is not the target. If other technologies were better we would [use them], for example, a small flywheel,” said Evan Chang-Siu, a mechanical engineering graduate student on the Berkeley team. “We analyzed the trade-offs and have come to the conclusion that tails are uniquely suited to this task.”
To undertake a project of this complexity and magnitude requires a remarkable level of interdisciplinary cooperation. Biologists had to work with engineers, who had to work with programmers and all of these groups had to work cohesively to make a working final product.
“The interdisciplinary team was the key to the whole project,” said Libby. “Not only did the lizards inspire the robot, but the robot was then used as a physical model to shape our hypothesis for the animals.”
The robots are not yet ready for large-scale use, but as researchers refine the design, the robots come closer and closer to real-life use in the field.