Rolling mechanism and performance of a soft robot driven by local curvature loading

Previous rolling soft robots are usually hard to achieve balanced rolling performance (terrain adaptability, rolling velocity and energy efficiency). This paper proposes a rolling soft robot driven by local curvature loading, which demonstrates good rolling velocity, small deformation rate, good energy efficiency and excellent terrain adaptability. A theory based on the energy method is established to analyze the rolling mechanism of the soft robot and to determine the critical loading curvature, which is validated by experiments. The local curvature loading causes the deformation of the entire robot configuration and results in the shift of the gravity center, which generates a gravity torque to drive the rolling of the soft robot when the critical loading curvature is reached. The proposed soft robot has good average rolling velocity (182.9 mm/s or 0.938 body length per second, BL/s) and can adapt to a variety of complex terrains such as the stairs (stair height 15 mm), the slope (slope angle 12.4 °) and the wide broken bridge (gap length 100 mm or 0.526 BL). The study in this work demonstrates broad application prospect in the fields of biomedical therapy, exploration, searching and rescuing, which provides a new idea for the structural design and performance improvement of rolling soft robots.