SIMPLIFIED MODELING AND SIMULATION OF RUDDER CONTROL FOR PARAMETRIC ROLLING REDUCTION IN SHIPS

Parametric rolling is a resonance phenomenon affecting the safety and operational performance of ships, especially in head or following seas. This paper investigates the possibility of attenuation of parametric roll oscillations by using rudder-based stabilization. To this goal, the ship is represented as a single-degree of freedom oscillator with nonlinear damping and time-varying nonlinear stiffness, subjected to a proportional-derivative (PD) control applied via the rudder. Numerical simulations are performed to measure the influence of the main model parameters, including control gains, initial conditions, encounter wave frequency, on the ship response in roll. Results demonstrate that PD rudder control are able to reduce substantially roll amplitudes for an extensive range of operating conditions. The findings provide insight into the effectiveness of rudder-based control of ship rolling and can be used as a foundation for future research using more complex ship models. Key words: parametric roll, rudder-based control.