Numerical Study on the Automatic Ballast Control of a Floating Dock

Abstract

Abstract Ballast control of a floating dock mainly relies on manual control, which requires highly skilled workers to master the ballast water system in several hours. Automatic control of the ballast water system can dramatically reduce the number of workers, improve operational efficiency, and increase safety during the vessel docking process. Motivated by this, this work studies the automatic ballast control of a floating dock and proposes a modified P-controller based on a numerical model for simulating the dynamic process of the floating dock’s operations. The numerical model includes a six-degree-of-freedom (6-DOF) model, a hydrostatic force model, a hydrodynamic force model and a hydraulic model. The hydrostatic force model is developed using the Archimedes law and a strip theory along the longitudinal direction. The hydrodynamic model is made based on the effects of added mass and dynamic damping. The hydraulic model is proposed to deal with the hydraulic calculation of the ballast water system. The present automatic ballast control is designed based on a proportional controller to control the valve opening angles when the pitch or roll angles are larger than corresponding threshold values. During the ballasting and de-ballasting operations without controllers, the roll angles of the dock reach value over 12°, which results from the asymmetric allocation of the ballast tanks. The present proportional controller can help stabilize the dock, i.e., keeping the pitch and roll angles within small allowable ranges of [−0.02°, 0.02°] and [−0.08°, 0.08°], respectively. The present automatic control will be further implemented in the vessel docking cases and can significantly improve the stability of the dock.