Design of the roll and heel reduction controller on ship's turning motion

When the ship turns, it will heel and exacerbate the roll triggered by the sea waves, ultimately impacting the safe navigation of the ship. A study was conducted on a design method for a roll and heel reduction controller based on nonlinear feedback to mitigate the ship's roll and heel during turning motion. A mathematical model was established for a ship with four degrees of freedom. Subsequently, a systematic analysis was conducted on the hydrodynamic force, rudder force, fin force and wave disturbance force of the ship. The ship's roll and heel motion are reduced by controlling the roll reduction force generated by the fin. The roll and heel reduction controller uses a nonlinear PID controller with parameters that vary with the feedback signal. This effectively enhances the dynamic response characteristics of the system. Simulations were performed to analyze the effect of different rudder angles and different fin angles on the performance of the ship's turning motion. The nonlinear feedback technique is employed to decrease the output of the fin angle, minimize the mechanical wear of fin stabilizer and save energy without compromising the control performance. The study analyzed the effect of a nonlinear feedback based controller in reducing roll and heel during turning motions of a ship. Simulations were conducted and compared with the classical PID controller method. The results indicated that the nonlinear feedback controller had a better performance in reducing roll and heel, validating the effectiveness of the designed method.