A Versatile and Robust Soft Rolling Robot Driven by Shape Memory Alloy

We present a soft rolling robot that is capable of fast locomotion on different terrains at over 1 body length per second. The palm-sized robot can endure falls from elevated heights and retain functionality after 40% compression of its body size. This highly deformable structure is composed of seven thermal actuators arranged in a star-shaped configuration. Tribological interactions with the ground are controlled by placing silicone rubber “shoes” at the tip of each vertex. Actuators are fabricated out of shape memory alloy wires that are sandwiched between two layers of silicone-coated thermally conductive rubber. One of the layers is pre-stretched resulting in a curved shape of the actuator. As the actuator is activated, it straightens and this deformation shifts the center mass leading to a rolling motion. Additionally, we developed a simulation tool based on the Discrete Elastic Rods modeling environment to inform the design and predict the locomotion of the robot. We vary the geometric and material parameters of the robot in the simulation and quantify its locomotion, with the aim of developing a more general-purpose, computationally-driven tool for designing soft robots.