A soft pipeline robot inspired by inchworm locomotion with layer-interference variable stiffness

Abstract Pipeline robots made from rigid materials have limited adaptability, making it difficult for them to navigate flexibly in complex, small-diameter pipes. In contrast, soft pipeline robots, constructed from flexible materials, can adapt to various pipe structures, making them well-suited for non-destructive testing. However, their lack of sufficient rigidity prevents them from achieving normal operational states under certain conditions. To address this issue, this paper presents the design of a soft pipeline robot using interlayer interference variable-stiffness technology. It includes a detailed kinematic analysis of the robot's bending deformation characteristics and stiffness variations under different air pressure conditions, chamber inflation states, and interlayer interference effects. Comprehensive in-pipe motion experiments were conducted to validate the findings. Both experimental and simulation results confirmed the effectiveness of the design, demonstrating the robot's superior performance and high operational efficiency in pipeline tasks. This research provides valuable insights into the application of soft robots for inspecting small-diameter, complex pipelines.