A proposal of the maneuvering motion model for low-speed operations in harbor

Accurately predicting low-speed maneuvering behavior before ship construction is essential for designing ships that enable safe and efficient harbor operations and for developing automatic berthing and unberthing systems. One of the typical methods for estimating maneuvering motions is simulation using a maneuvering motion model. However, the conventional maneuvering motion models have limitations in representing low-speed hydrodynamic forces, failing to capture specific maneuvering phenomena and reducing simulation accuracy. This study proposes an improved maneuvering motion model to address these limitations. The model formulates hydrodynamic forces acting on the hull and rudder for arbitrary inflow directions, allowing for the consideration of large drift angles caused by side thruster usage. Additionally, it accounts for propeller operations in all four quadrants, which significantly influence rudder forces, thereby improving prediction accuracy. The model was developed based on captive model tests (CMTs) and validated through free-running model tests (FRMTs). The validation results demonstrate that the proposed model can accurately capture the low-speed maneuvering motions. By utilizing this model, low-speed maneuvering performance can be evaluated during the design phase, contributing to the development of safer ships. Furthermore, employing simulations before ship construction can optimize control parameters for automatic berthing and unberthing systems, reduce the need for extensive real-world testing and enhance overall system reliability. • A new mathematical model for low-speed maneuvering is proposed to address limitations of conventional MMG models. • The model incorporates hydrodynamic forces associated with low-speed maneuvering, including large drift-angle motions from side thruster operation and astern movements due to propeller reversal. • Hydrodynamic forces are formulated under arbitrary inflow conditions for the hull and rudder, and across all four propeller quadrants for the propeller and rudder. • The model is validated through free-running model tests, confirming its ability to reproduce low-speed maneuvering behavior. • The proposed model is expected to be used for evaluating low-speed maneuvering performance during the ship design stage and for optimizing control parameters of automatic berthing and unberthing systems.