200220 robot snake

Snakes in the lab, but all is well

Ophiophobes might suggest we have enough real snakes in the world without creating artificial ones.

A robot snake in the Terradynamics Lab at Johns Hopkins University. Credit: JHU/Will Kirk

On the other hand, engineers (presumably those who aren’t ophiophobes) see it as an important stage in the development of robots that can operate in tricky terrain, and thus potentially do search and rescue work.

Now a team from Johns Hopkins University in the US says it has taken the next step by creating a snake robot that can nimbly climb large steps.

Chen Li, senior author of a paper published in the Journal of Experimental Biology and Royal Society Open Science, says previous studies have mainly observed snake movements on flat surfaces, which doesn’t take account of obstacles such as rubble and debris.

He and his team decided to study the variable kingsnake (Lampropeltis Mexicana Thayeri), which lives in both deserts and pine-oak forests and moves easily and frequently over large boulders and fallen trees.

They let a few snakes loose in the lab and ran a series of experiments, changing step height and surface friction to observe how they contorted their bodies in response to the barriers.

They found that the snakes partitioned their bodies into three sections: the front and rear wriggled back and forth on the horizontal steps, like a wave, while the middle remained stiff, hovering to bridge the large step. The wriggling portions provided stability to keep the snake from tipping over.

As the snakes got closer and onto the step, the three body sections travelled down each body segment. As more and more of the snake reached the step, its front body section would get longer and its rear section would get shorter while the middle body section remained roughly the same length, suspended vertically above the two steps.

If the steps got taller and more slippery, the snakes would move more slowly and wriggle their front and rear body less to maintain stability.

After analysing their videos and noting how snakes climbed steps in the lab, graduate student Qiyuan Fu created a robot to mimic the animals’ movements.

At first, it had difficulty staying stable on large steps, so the researchers inserted a suspension system into each body segment so it could compress against the surface when needed. The only downside was this required more electricity.

Li says the resulting snake robot was faster and more stable than others he is aware of, and even came close to mimicking a real snake’s speed.

CREDIT: Patrick Ridgely, Dave Schmelick, Len Turner/Johns Hopkins University Office of Communications.