Kinematics-constrained Path Planning of Multiple Underwater Robots for Ship-bottom Fishing-net Removal

This study proposes a three-dimensional multi-robot path-planning framework that enables multiple remotely operated vehicle (ROV)-based work robots to reach designated work points for ship-bottom fishing-net removal simultaneously while avoiding collisions. The motion of the target platform is represented by a finite set of motion primitives covering cruise, acceleration and deceleration, yaw turning, lateral (sway) and vertical (heave) motion, and hovering. A kinematics-constrained extension of Safe Interval Path Planning (SIPP) uses these primitives as low-level state transitions, so that each trajectory satisfies the position, heading, and velocity constraints of the platform while avoiding static structures during its safe time intervals. Continuous Conflict-Based Search (CCBS) then detects inter-robot conflicts in continuous time and resolves them by adding spatiotemporal constraints and replanning for only the affected robot. In three work scenarios built from a ship CAD model, the minimum inter-robot distance remained above the required ROV separation distance of 2.40 m in every case, with a minimum observed value of 2.718 m across all three scenarios, and the detected conflicts were resolved by inserting 7.5 s and 15.0 s of hovering. Furthermore, the proposed path-planning framework was evaluated for its applicability to other underwater robotic platforms beyond ROVs. With only the platform-dependent primitives replaced by those of an autonomous underwater vehicle (AUV) model, 250 simulation runs across five seabed terrains involving 2 to 10 AUVs maintained the required AUV separation distance of 2.668 m, with a minimum observed inter-AUV distance of 2.7031 m, suggesting that the same SIPP-CCBS structure applies to platforms with different motion constraints.