An Air-Jet Continuum Robot for Industrial Integrated Fluidic Circuit Inspection

Industrial fluidic circuits operating under long-term extreme conditions are prone to defects such as cavitation, corrosion, and cracks, raising a critical demand for in-situ robotic inspection. Traditional manual disassembly-based methods are inefficient, while existing robots lack the ability to simultaneously adapt to complex geometries and maintain stable adsorption on surfaces of varying curvature. This study proposes an air-jet continuum robot (AJCR) that integrates three core modules: air-jet modules, a unit flexible continuum skeleton (UFCS), and stiffness-adjustable flexible suction cups (FSCs), enabling effective crawling and inspection inside integrated industrial fluid circuits. The UFCS provides omnidirectional bending capability of up to 196° enabling navigation through complex channels including abrupt turns of 120° inside stop valves. Under an input pressure of 0.8 MPa, the AJCR generates a maximum air-jet counter-thrust of 4.72 N for adsorption and 4.16 N for driving, ensuring reliable locomotion on unstructured, slippery, and discontinuous surfaces. Based on the sliding suction strategy, the FSC offers a maximum static adsorption force of 35.1 N, reduces sliding friction to 2.25 N on stainless steel, and adapts to curved surfaces with radii as small as 125 mm, facilitating stable sliding adsorption even across welded seams. Experimental results demonstrate that the AJCR smoothly navigates pipeline systems, enters stop valves, mixed-flow pumps and pressure vessels, and operates in liquid-filled environments, significantly improving inspection coverage and operational safety in fluidic delivery systems.