Snakebot Unveils Sidewinder Secrets
Sidewinder rattlesnakes are unusual in how they quickly travel across deserts and are able to climb steep sand dunes. Observing the creatures in motion, US scientists from Pittsburgh’s Carnegie Mellon University created a robot snake, designed to mimic the movements.
However, it was found that these Snakebots – one of which was nicknamed “Elizabeth” – were only loosely based on the creatures’ movements. The robots were able to quickly travel across level ground, but weren’t able to make the ascent over steep dunes.
Elizabeth in particular was found to struggle with such dilemmas in Egypt. Part of the robot’s body would press into the sand in order to push itself up the sandy hills, only for the sand to slip away beneath it and bring the Snakebot back to where it started.
Dr Daniel Goldman, senior author of the paper, explained that originally it was thought that sidewinders were able to climb sand dunes in the manner they do by digging their bodies deeper into the sand.
To check out this theory, the team filled a mechanical bed with sand from the Arizona desert the snakes hailed from. This bed was able to tilt to simulate sand dunes of different degrees of steepness.
The snakes were placed in the makeshift desert and filmed using high-speed video cameras as the dune was tilted to create steeper and steeper climbs for the creatures.
The team noted that every time the dune was made steeper, the sidewinders were still able to ascend. To do this, the snakes would flatten their bodies so that they had more contact with the sand as they climbed. The steeper the ascent, the more smoothly the snakes would flatten themselves.
Investigating this further, the team found that the snakes’ bodies undulated both left-to-right and up-and-down, but ever so slightly out of sync.
Applying this newfound knowledge to Elizabeth, they found that allowing the robot to get just the right amount of contact with the sand enabled it to climb a sand dune to the same degree as one of the snakes.
Professor Howie Choset, Elizabeth’s creator, compared the motion of a sidewinder to the tread of a tank. As the treads are placed down in front in the direction of travel, treads at the back are being picked up. “The snake lifts some body segments while others remain on the ground,” he explained.
Using this undulation motion allows both the snakes and the robot to maintain the stability of the sand beneath them, so they have enough of a grip to ascend without the sand flowing away in their wake.
“Our initial idea was to use the robot as a physical model to learn what the snakes experienced,” Dr Goldman described. “By studying the animal and the physical model simultaneously, we learned important general principles that allowed us to not only understand the animal, but also improve the robot.”