Morphology analysis of a thin elastic ring under gravity for configuration design of rolling soft robots

The rolling soft robot usually uses circular or ellipse-like configurations but the factors influencing the robot configuration have not been sufficiently investigated. This study presents a theoretical model for investigating the morphology evolution of a thin elastic ring under gravity. The ring exhibits an ellipse-like morphology under gravity, with this morphology governed by the ratio of gravity to bending stiffness. An increase in the ratio of gravity to bending stiffness results in a flatter ellipse-like structure, accompanied by an enhanced contact length with the ground and a concomitant reduction in its gravitational moment on the slope. The ellipse-like structures calculated by the theory are in good agreement with the experiment and simulation. This study provides a theoretical basis for the material selection and geometry determination of the configuration design of required rolling soft robots.