In recent years, when booming robotics engineering has provided the world a way to traverse nearly all unbearable terrains including space, the sandy surfaces of desert dunes and beaches have often provided an unscalable feat for researchers. A granular substrate, which moves like fluid, sand is a particularly challenging terrain for most species, which is only one reason why so few species inhabit the desolate deserts. But in looking for a way to make it through the sandy slopes, researchers looked to the snake species of the deserts to create a sidewinder rattlesnake robot that could slither its way through the sand.
Developed by a team at Georgia Tech, researchers recently described their findings in this week's issue of the journal Science, which tested a robotic snake look-alike to the real thing. Running both real and robotic snakes through identical sandy obstacle slopes, the researchers were able to view the sidewinder rattlesnake's movement in an entirely new light, shedding insight on how to harness that movement to make robotics even better.
The species Crotalus cerastes, known commonly as the sidewinder rattlesnake, is a staple of northwestern Mexico and the southwestern United States. Masters of the deserts, the sidewinder is an unconventional slitherer in comparison to its other snake relatives. Rather than a fluid, straightforward slither that propogates movement forward with the contractions of the snake's outer muscles, the sidewinder pulls itself forward and over hot dunes by leverage parts of its body in a zig-zag movement.
"It's a crazy-looking gait" lead author and physicist at Georgia Institute of Technology, Daniel Goldman says. "There are field biologists who've studied these animals, and they say if you look at sidewinding too long, you'll go mad."
For quite some time now, researchers have worked on snake-like robots in hopes of potentially developing tools vital in archaeological expeditions and search & rescue missions, however, the movement of these early robots has not quite mastered replicating that of real snakes. Still mechanical in its movement, the robots have still found traversing sand dunes a challenging feat. One such robot, named Elizabeth, was developed by the roboticist and co-author of the paper Howie Choset by Carnegie Mellon University, for an archaeological mission in Egypt. Deployed with the task of searching ancient Egyptian caves, though to hold artifacts millennia old, Elizabeth was unable to surpass the sandy monoliths that lay in front of her and eventually slipped over on a sandy slope.
And in hopes of perhaps improving the robotics of these "snakes" to better replicate the movement of their organic dopplegangers, Choset decided to collaborate with Goldman and his team to try and discover what biomechanics create this unique sidewinding ability. By testing the venomous rattlesnakes' ability to move across sandy inclines as high as 20 degrees, the researchers were able to find that the sidewinders were increasing the contact length of the "zig" segments of their bodies with the sand, allowing them to propagate forward pulling their "zag" segments of the body without getting stuck in the sand. And the changes, when incorporated into the snake robot's software bodyplan movement, allowed the robotic dopplegangers to traverse sandy hills that it once found impossible to overcome.
"The work of these researchers 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" Virginia Tech researcher, not involved with the study, John Socha said in a review of the study published in the journal Science. "The drive to understand the mechanics of sidewinding has brought us one step closer to achieving lifelike locomotion in robots."
