Modeling ship movements under automatic mooring system with consideration of harbor oscillations

Abstract

As vessel sizes increase, conventional mooring systems struggle to provide the stability and safety required for modern loading operations. Automatic mooring systems offer a viable alternative and have been successfully implemented in ports worldwide. However, current research lacks sufficient understanding of their operational performance under different sea conditions, particularly under severe scenarios such as long-period waves and harbor oscillations. This study presents a numerical model for an automatic mooring system based on a Proportional-Derivative (PD) controller. The research examines the vessel's response under various control settings and assesses the system's efficacy during harbor oscillations.

The numerical results demonstrate that the proportional and derivative parameters play a crucial role in the response amplitude and resonant frequency of the moored vessel: an increased proportional parameter results in a higher resonant frequency but at the expense of a larger motion amplitude, whereas the derivative parameter exhibits the converse effect. Furthermore, compared with the traditional mooring system, the automatic mooring system based on a PD controller can effectively suppress the vessel's horizontal motion under harbor oscillation conditions, which is significant for enhancing the safety and operational efficiency of ports in extreme sea states.