Sidewinding with minimal slip: Snake and robot ascent of sandy slopes

TL;DR

This study investigates how sidewinder rattlesnakes and a robotic model adapt their contact length to effectively ascend sandy slopes, revealing strategies to mitigate slipping on granular media.

Contribution

It uncovers the mechanism of contact-length control in sidewinding snakes and implements it in a robot to improve ascent on sandy slopes.

Findings

Snakes increase body contact length on steeper slopes.

Robotic model successfully ascends near maximum slope stability.

Granular yield stress decreases with incline angle.

Abstract

Limbless organisms such as snakes can navigate nearly all terrain. In particular, desert-dwelling sidewinder rattlesnakes (Crotalus cerastes) operate effectively on inclined granular media (such as sand dunes) that induce failure in field-tested limbless robots through slipping and pitching. Our laboratory experiments reveal that as granular incline angle increases, sidewinder rattlesnakes increase the length of their body in contact with the sand. Implementing this strategy in a physical robot model of the snake enables the device to ascend sandy slopes close to the angle of maximum slope stability. Plate drag experiments demonstrate that granular yield stresses decrease with increasing incline angle. Together, these three approaches demonstrate how sidewinding with contact-length control mitigates failure on granular media.