A time-domain method for analyzing the ship roll stabilization based on active fin control

Abstract

The present work focuses on the development of a numerical body nonlinear time-domain method for estimating the effect of active roll fin stabilizers on ship roll motion in both regular and irregular seaway. The time-domain analysis aims at providing fast and accurate ship responses that will be useful during the design process through accurate estimation of the environmental loads. A strip theory-based approach is followed where the Froude-Krylov and hydrostatic forces are calculated for the exact wetted surface area for every time step. The equations of motions are formulated in the body frame and consider the six degrees of coupled motions. The active fin, rudder, and propeller modules are included in the simulation. This leads to accurate modeling of the system dynamics. The numerical unstabilized roll motion is validated with experimental seakeeping simulations conducted on a Coastal Research Vessel (CRV). The phenomena of Parametric Rolling (PR) is identified during the numerical investigation of the candidate vessel. Besides, a nonlinear PID (NPID) control technique and LQR method is implemented for active roll motion control and its performance is observed in regular as well as irregular waves. The proposed numerical approach proves to be an effective and realistic method in evaluating the 6-DoF coupled ship motion responses.