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Could the Sidewinder Snake Robot Help Search and Rescue Missions?

Georgia Tech research offers new insight into making better search and rescue robots.

Meet the sidewinder rattlesnake robot! This mechanical serpent can actually move across sandy surfaces, both flat and inclined — a feat that has escaped engineers until now.

In a project described in the journal Science, a team led by Georgia Tech researchers ran snakes, both robotic and real, across a challenging sandy slope. The results offer a fresh take on how sidewinder snakes move, as well as new insight into making better search and rescue robots.

Snakes never let a lack of legs keep them down. These limbless reptiles can climb trees, swim and even glide through the air, depending on the species. But even moving on the ground comes with its challenges — particularly if it’s on sand, a granular substrate that’s made of tiny solids but moves like a fluid. (Anybody who has tried running through sand knows how difficult it can be.) Scientists are still studying how various animals move across such challenging terrain, particularly on dunes and hills.

The sidewinder, known formally as Crotalus cerastes, has clearly mastered the art of traversing the sandy deserts of the Southwestern United States and northwestern Mexico. Its zigzagging body sidles across hot deserts, using the “zig” segments of its curving body for purchase as it lifts up the “zag” segments. It looks very different from the comparatively straightforward slither of your typical snake.

"It's a crazy-looking gait," said senior author Daniel Goldman, a physicist at the Georgia Institute of Technology. "There are field biologists who've studied these animals, and they say if you look at sidewinding too long, you'll go mad."

Researchers have long worked on snake-like robots, potentially useful for traversing rough terrain or entering damaged buildings in search of survivors. One such robot built by Howie Choset, a roboticist at Carnegie Mellon University and co-author of the study, was deployed on an archaeological mission to search ancient Egyptian caves thought to hold artifacts that were thousands of years old. But the robot, called Elizabeth, slipped and pitched over on a sandy slope.

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Choset, who has spent years building robotic snakes, teamed up with Goldman to see whether they could use the robot to understand how the sidewinder was moving — and perhaps improve the robot in the process.

The researchers went to the Yuma Desert in Arizona to find sidewinder rattlesnakes to study — and they even brought back sand from the desert to make sure the animals would be traversing natural terrain. (Lead author Hamidreza Marvi, then at Georgia Tech and now at Carnegie Mellon, even dug up some of it himself.) They took the animals to a shed in the back of Zoo Atlanta and tested them on flat and slanted sandy surfaces.

"The snakes were quite venomous, and we were not allowed to bring them to Georgia Tech," Goldman said.

The scientists found that the animals managed to move across inclines as high as 20 degrees (just 7 degrees shy of when sand will start flowing downhill with any disturbance). The sidewinders were using a neat trick — they increased the contact length of the “zig” segments of their bodies with the sand, allowing them to move without getting stuck.

When they incorporated this change into the snake robot’s software, they found that the robot was much better able to handle sandy inclines that before would have left it wriggling helplessly.

And when the researchers ran 13 other closely related pit viper species through the gantlet to see whether they would be able to traverse the sand, they too writhed to no effect. They lacked the neural “software” to adopt the sidewinder’s expert gait, and unlike the robot, they couldn’t get an upgrade.

“This suggests that the evolution of sidewinding may have required a change in neuromotor control, shifting the timing of muscle activation to match the required template for sidewinding,” John Socha of Virginia Tech, who was not involved in the paper, wrote in a commentary on the study.

The researchers say they’re excited about the light that the robot sheds on how snakes move in real life, and about the insight the snakes provide into building a better, more agile robot. It’s mutually beneficial for biology and engineering, Goldman said. The robot isn’t just an end product of studying nature: It’s also a tool to better understand nature.

Socha appeared to agree.

“The work of Marvi et al. demonstrates the strength of integrating biology, engineering, and physics, providing the finest example to date of the reciprocal use of animals and robots for mutual illumination,” he wrote. “The drive to understand the mechanics of sidewinding has brought us one step closer to achieving lifelike locomotion in robots.”

©2014 the Los Angeles Times. Distributed by MCT Information Services.