Experimental Mechanics of a Highly Articulated Backbone for Soft Snake Robots

Backbones are a critical component of bioinspired snake robots, providing structural support and actuator attachment points. Current soft snake robots overwhelmingly rely on continuum backbones, which are continuous strips or rods. Continuum backbones are straightforward to manufacture and integrate, but also tie torsional stiffness, bending stiffness, buckling load and maximum curvature, e.g., increasing cross-section size to raise buckling load must increase bending stiffness in at least one direction. Biological snakes, in contrast, have highly articulated backbones that break these scalings but also have complex vertebra geometry and musculature to manage the articulation. In this work, we develop and test a concept for a highly articulated, snake-inspired backbone and a corresponding actuator layout with two actuator types. The artificial vertebrae and actuator layout include versions of key features identified in biology literature, such as articulation points and motion limiters. We experimentally identify bending range of motion in two planes, note emergent twist, and demonstrate locomotion. While only a first step, this work demonstrates a potential alternative approach to soft snake robot design, and suggests that increasing mechanical complexity of soft robots may be more tolerable than previously assumed. Emergent behaviors suggest a path forward for producing complex movements from simple actuation inputs, but further work is needed to model robot mechanics.