Earthworm-inspired multimodal pneumatic continuous soft robot enhanced by winding transmission

A research paper by scientists at Tianjin University presented an earthworm-inspired multimodal pneumatic continuous soft robot enhanced by wire-winding transmission.

The research paper, published on Mar. 19, 2025 in the journal Cyborg and Bionic Systems, proposes an earthworm-inspired multimodal pneumatic continuous soft robot to simultaneously achieve multimodal motion and good motion performance. Using the derived overlapped continuous control law (DOCCL) and wire-winding transmission, the robot can achieve a maximum planar crawling speed that surpasses that of other robots of the same type by an order of magnitude.

With the increasing demand for robots in irregular and complex environments, traditional rigid robots have limitations in adapting to complex environments, while soft robots have become a hot research topic due to their flexibility and good environmental interaction capabilities. Inspired by the efficient peristaltic movement of reptiles such as earthworms, researchers have been committed to developing soft robots that can perform multimodal movements in pipelines, soil, and even within the human body. “However, existing earthworm inspired soft robots often adopt a single motion mode, which limits their applicability and motion efficiency.” said the author Jianbin Liu, a professor at Tianjin University, “Therefore, we aim to break through the existing technological bottlenecks and propose a new strategy for multimodal motion to enhance the overall motion performance and environmental adaptability of soft robots.”

First, the study introduces a continuous control strategy (DOCCL) based on the superposition of multiple peristaltic waves to accurately emulate earthworm locomotion; then, it presents an innovative wire-winding transmission mechanism that converts the extension of one segment into the synchronized contraction of others, thereby significantly enhancing movement efficiency; next, the authors design and fabricate a soft robot employing silicone materials that integrates both actuation and steering functionalities; subsequently, an autonomous obstacle-avoidance control strategy, grounded in piezoelectric sensor-based contact force detection, is developed to enable real-time navigation adjustments; finally, the multimodal locomotion capabilities of the robot are rigorously validated through comprehensive experiments—including planar, pipeline, and cross-plane crawling tests—which collectively demonstrate substantial improvements in both speed and overall performance.

This continuous control strategy based on the superposition of multiple peristaltic waves (DOCCL) proposed in this study, combined with the innovative wire-winding transmission mechanism, significantly enhances the locomotion efficiency of the soft robot. Experimental results demonstrate that the robot achieves an average planar crawling speed of 6.65 mm/s and a pipeline crawling speed of 1.66 mm/s, with notable improvements of 249.5% and 38.9% respectively compared to configurations without wire-winding. Moreover, the autonomous obstacle-avoidance strategy based on piezoelectric sensor-based contact force detection effectively enables real-time navigation adjustments, further contributing to its superior overall performance. “In conclusion, Our robot’s multimodal capabilities and enhanced motion efficiency demonstrate superior overall performance, and this robot has good potential for medical and industrial applications.” said Jianbin Liu.

Authors of the paper include Jianbin Liu, Pengcheng Li, Zhihan Huang, Haitao Liu, and Tian Huang.

This work was supported in part by the National Natural Science Foundation of China under grant nos. 52475067, 52325501, and 91948301.

The paper, “Earthworm-Inspired Multimodal Pneumatic Continuous Soft Robot Enhanced by Winding Transmission” was published in the journal Cyborg and Bionic Systems on Mar. 19, 2025, at DOI: 10.34133/cbsystems.0204.

END