Design and optimization of a novel multi-sphere hose-linked robot configuration for pipeline inspection

Objectives To improve the waterproof reliability, locomotion efficiency, and elbow maneuverability of robots used for shipboard water-filled pipeline inspection, a novel pipeline inspection robot featuring high waterproof integrity, low-energy-consumption propulsion, and strong elbow-passing capability is proposed.

Methods A multi-objective optimization framework is developed for the shipboard pipeline inspection robot. The robot's envelope dimensions are optimized by jointly considering hydrodynamic drag, internal space requirements, and layout constraints of sensors/actuators. The Pareto-optimal solutions are obtained using the NSGA-II algorithm. A hydrodynamic model of the robot is then established, and CFD simulations are conducted under representative inflow conditions to analyze the velocity field, vortex structures, and pressure-coefficient distributions, thereby evaluating the effects of the robot configuration on drag and flow-separation characteristics. Finally, waterproof tests in water-filled pipelines, 90° elbow passability tests, and visual inspection experiments in an actual water-supply pipeline are carried out to validate the proposed design.

Results Numerical simulation results indicate that the proposed configuration achieves an overall drag coefficient of 0.45 under representative inflow conditions. Experimental results demonstrate stable operation in water-filled pipelines and successful traversal of a 90° elbow. The robot is applicable to pipelines with diameters ranging from 100 mm to 400 mm and achieves a maximum traveling speed of 0.5 m/s. In the real water-supply pipeline test, the robot is capable of transmitting real-time first-person-view images, enabling visual identification of internal pipeline features such as joints, wear marks, and suspected cracks.

Conclusions The proposed three-sphere waterproof robot configuration effectively improves propulsion efficiency and turning stability in water-filled pipelines with elbow sections while maintaining reliable sensor integration and sealing performance. The proposed design therefore provides a practical reference for the development and engineering application of shipboard pipeline condition-monitoring devices.