Journal of Bionic Engineering (2025) 22:1071–1084https://doi.org/10.1007/s42235-025-00682-z

Untethered Soft Crawling Robot Based on Origami Inspired Soft-rigid Hybrid Actuator

Jianbin Liu1  · Guoyu Ma1  · Tianyu Zhang1  · Xianlei Shan1  · Rongjie Kang1  · Rencheng Zheng1  · Haitao Liu1

1 Key Laboratory of Mechanism Theory and Equipment Design of Ministry of Education, Tianjin University, Tianjin 300072, China

Abstract 

This paper presents an untethered pneumatic soft robot which can crawl both in horizontal and vertical pipes with different sizes and cross sections. This robot uses modular origami inspired soft-rigid hybrid actuator to produce telescoping and anchoring movements powered by vacuum pressure. The introduction of grooves to valley crease significantly lowers the full contraction vacuum pressure and improves the response, allowing the system can be driven by an onboard micro vacuum pump, enabling the possibility of miniaturization, integration, and untethered operation of the robot. A series of crawling experiments in pipes with different sizes and cross sections constructed by acrylic are conducted to validate the crawling performance of the robot. Within square cross-section pipes, the robot can achieve a velocity of 9.4 mm/s in horizontal crawling and 7.7 mm/s in vertical upward crawling. For horizontal crawling in circular pipes, it can reach a velocity of 8.0 mm/s. When fully charged, the robot can crawl for 40 min with a mileage of 16.649 m, which is sufficient for most drainage and industrial pipelines detection tasks. The robot demonstrates excellent endurance and speed performance that exceed most existing untethered soft pipe crawling robots. 

Keywords Crawling robot · Soft-rigid hybrid actuator · Untethered · Origami actuator · Pipe detection