Journal of Bionic Engineering (2024) 21:694–706 https://doi.org/10.1007/s42235-024-00487-6 

Modular Soft Robotic Crawlers Based on Fluidic Prestressed Composite Actuators 

Zefeng Xu1  · Linkai Hu2  · Longya Xiao1  · Hongjie Jiang1  · Yitong Zhou1 

1 Shien-Ming Wu School of Intelligent Engineering, South China University of Technology, Guangzhou 511442, China 2 School of Mechanical and Electrical Engineering, Guangzhou University, Guangzhou 510006, China

AbstractSoft robotic crawlers have limited payload capacity and crawling speed. This study proposes a high-performance inchwormlike modular robotic crawler based on fuidic prestressed composite (FPC) actuators. The FPC actuator is precurved and a pneumatic source is used to fatten it, requiring no energy cost to maintain the equilibrium curved shape. Pressurizing and depressurizing the actuators generate alternating stretching and bending motions of the actuators, achieving the crawling motion of the robotic crawler. Multi-modal locomotion (crawling, turning, and pipe climbing) is achieved by modular reconfguration and gait design. An analytical kinematic model is proposed to characterize the quasi-static curvature and step size of a single-module crawler. Multiple confgurations of robotic crawlers are fabricated to demonstrate the crawling ability of the proposed design. A set of systematic experiments are set up and conducted to understand how crawler responses vary as a function of FPC prestrains, input pressures, and actuation frequencies. As per the experiments, the maximum carrying load ratio (carrying load divided by robot weight) is found to be 22.32, and the highest crawling velocity is 3.02 body length (BL) per second (392 mm/s). Multi-modal capabilities are demonstrated by reconfguring three soft crawlers, including a matrix crawler robot crawling in amphibious environments, and an inching crawler turning at an angular velocity of 2? /s, as well as earthworm-like crawling robots climbing a 20?  inclination slope and pipe. 

Keywords Soft robot · Soft crawler · Fluidic prestressed composite · Kinematic model · Enhanced loading · Multi-modal capability