Abstract: Earthworm-inspired soft robots hold promise for navigating complex environments, yet they are often constrained by actuator performance, biomimetic locomotion, and untethered operation. In this study, we present an untethered bionic earthworm-like robot based on Yoshimura-ori soft structure and continuous peristaltic wave gait. Firstly, two segment configurations derived from the Yoshimura-ori structure are proposed: the annular chamber configuration and the central chamber configuration, achieving excellent expansion rates of 54.32% and 78.07%, respectively. Secondly, a comparative analysis of discrete versus continuous peristaltic wave gaits is conducted on robots with these two configuration. The results reveal that the continuous peristaltic wave gait yields higher locomotion velocity than the discrete gait. Under the continuous peristaltic wave gait, the robot with the central chamber configuration exhibits outstanding performance, with a planar locomotion velocity of 12.63 mm/s and a pipeline locomotion velocity of 9.05 mm/s. Finally, a modular untethered robot prototype is constructed, and locomotion experiments confirm that the untethered robot also maintains excellent motion performance. Moreover, the untethered robot successfully traverses varied terrains, demonstrating its outstanding environmental adaptability, feasibility and practical potential.

Key words: Soft robot')">Soft robot, Yoshimura-ori actuator, Continuous peristaltic wave gait, Untethered robot