Motion Pattern Analysis of a Rolling Locomotion Robot Featuring Dual Rimless Wheels and Elastic Connectors

Abstract

Rimless wheel, one of the simplest walking models, has been widely studied as a theoretical framework for bipedal locomotion. This study introduces a dual rimless wheel (DRW) connected by elastic elements for maintaining the body shape and investigates its passive locomotion capability through numerical simulations. Simulation results reveal that as the stiffness of the elastic elements increases, the walking behavior approaches that of a rigid rimless wheel, resulting in higher forward velocity. Conversely, lower stiffness enhances body flexibility and enables the generation of low-speed gaits with remarkably small energy loss. These findings suggest that the DRW may be advantageous in environments where collisions have strong impacts, such as compliant terrains. Furthermore, through comparative simulations with several other models, including the rigid rimless wheel, we demonstrate that the low-stiffness DRW model can generate clearly slower passive locomotion while maintaining a feasible walking region. On the other hand, basic prototype experiment indicates that the low-stiffness DRW model achieves more stable and faster walking than the high-stiffness DRW model in low-angle slopes. While the results do not imply that the DRW is universally optimal, they provide new insights into generating soft and stable gaits and underline the usefulness of tensegrity mechanisms.