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

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

Methods A multi-objective optimization framework is proposed for a ship pipeline inspection robot. The robot’s envelope-size parameters 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 configuration on drag and flow-separation characteristics. Finally, waterproof tests in water-filled pipelines, 90° elbow passability tests, and visual inspection experiments in a real water-supply pipeline are performed for validation.

Results Numerical simulations indicate that the proposed configuration achieves an overall drag coefficient of 0.45 under a representative inflow condition. Experiments demonstrate stable operation in a water-filled pipeline and successful passage through a 90° elbow. The robot covers a pipe-diameter range of 100–400 mm, reaches a maximum traveling speed of 0.5 m/s. In the real water-supply pipeline test, the robot streams real-time first-person images, enabling visual identification of internal features such as joints, wear marks, and suspected cracks.

Conclusions The proposed three-sphere waterproof robot configuration effectively enhance propulsion efficiency and turning stability in water-filled elbowed pipelines, while maintaining sensor integration and sealing reliability, thereby providing a practical reference for the design and engineering application of shipboard pipeline condition-monitoring devices.