Watch These Slithering Robots Climb Like a Sidewinder

Snakes on an inclined plane.

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Serpentine robots can now scale sandy slopes, an advance that could allow slithering droids to go where no bot has gone before.

The potential use for these robots "that is nearest and dearest to my heart is urban search and rescue — I want to enable rescue workers to identify survivors in collapsed structures as quickly and safely as possible," Choset says. "We're also interested in getting these robots into pipes, such as in nuclear power plants and in sewers."

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Shipping Sands

Conventional robots are good at rolling or walking across hard, flat surface. They're not so good at traversing anything else. That's why scientists have looked to limbless animals such as snakes for inspiration, since these creatures can navigate on, up, and over sand, dirt, bark, or water without getting stuck.

Roboticist Howie Choset at Carnegie Mellon University in Pittsburgh led a team that over the past two decades has developed a line of snake robots capable of sidewinding and pole-climbing. But on an archaeological mission in Egyptian Red Sea caves in 2011, one of their robots, Elizabeth, failed in its attempts to climb up a sandy slope, instead slipping and pitching over.

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Choset's team needed to study how real serpents tackle sandy slopes. So the researchers built a tiltable bed of sand in Zoo Atlanta with ready access to a variety of species of snakes. They focused on the sidewinder rattlesnake, an expert on traversing desert dunes, and even shipped in hundreds of pounds of sand from the Yuma Desert of Arizona, where these reptiles are from.

"To me, this is a beautiful illustration of how far people will go to understand something to its core," says Jake Socha, a biomechanist at Virginia Tech in Blacksburg, who did not take part in this study.

The Secrets of Sidewinding

When rattlesnakes move via sidewinding, they lifting certain parts of their bodies while keeping others in contact with the ground to minimize slip. Prior studies had investigated sidewinding on hard surfaces, but how it works on loose, flowing material is a hard problem. So Choset's team used high-speed video cameras to watch six sidewinder rattlesnakes, which did not slip even as the incline of the slope increased, and several of their pit viper relatives, which could not climb the slope.

The secret of the sidewinders lies not just in how deeply they penetrated the sand, but also how much contact they made with the underlying surface. As the incline grew steeper, the snakes increased the percentage of their body area in contact with the sand and decreased the amount of their bodies lifted in the air.

The scientists then implemented this change in a robotic snake they built that was two inches in diameter and 37 inches long, and consisted of 16 joints and 17 segments. With the change in place, the bot behaved a lot more like a real snake, able to climb slopes it previously could not.

"What's most interesting about this study to me is how we've learned something new about both animals move and how to make robots do the same thing," Socha says. "Learning from the snake enabled the researchers to tweak their robot to be able to go up slopes, and now the robot serves as a platform for new experiments that helps scientists learn more about how snakes move."

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