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

To improve the waterproof reliability, locomotion efficiency and elbow maneuverability of robots for shipboard water-filled pipeline inspection, a novel pipeline inspection robot with high waterproof reliability, low-power propulsion and excellent elbow passability is proposed.

A multi-objective optimization framework is established for the shipboard pipeline inspection robot. The envelope dimensions of the robot are optimized with comprehensive consideration of hydrodynamic drag, internal space requirements and layout constraints of sensors and actuators. The Pareto-optimal solutions are solved by the NSGA-II algorithm. A hydrodynamic model of the robot is built, and CFD simulations are performed under typical inflow conditions to analyze the velocity field, vortex structures and pressure coefficient distributions. The influences of the robot configuration on drag and flow separation characteristics are evaluated accordingly. Finally, waterproof tests in water-filled pipelines, 90° elbow passability tests and visual inspection experiments in actual water-supply pipelines are implemented to verify the proposed design.

Numerical simulation results show that the overall drag coefficient of the proposed configuration is 0.45 under typical inflow conditions. Experiments prove that the robot can operate stably in water-filled pipelines and realize smooth passage through a 90° elbow. It is suitable for pipelines with diameters of 100 mm to 400 mm, and its maximum moving speed reaches 0.5 m/s. In the test of actual water-supply pipelines, the robot can transmit real-time first-person-view images, which supports the visual identification of pipeline inner wall features including joints, wear marks and potential cracks.

The proposed three-spherical waterproof robot configuration can effectively enhance the propulsion efficiency and turning stability in water-filled pipelines with elbows, while ensuring reliable sensor integration and sealing performance. This design provides a valuable reference for the structural design and engineering application of condition monitoring devices for shipboard pipelines.