Nonlinear hydrodynamic model based course control and roll stabilization by taking rudder and propeller actions

The aim of this study is to control the course and roll motion for ships advancing in a seaway through taking the rudder and propeller actions. A high-fidelity model of the container ship is adopted and validated by using the data of the free-running model test. The full-scale sea trial data are analyzed to improve the simulation characteristics of the actuator to avoid the severe wear problem caused by overusing of the steering machine. In the present study, the adaptive robust controllers are designed for the nonlinear hydrodynamic model to achieve the overall optimal control performances of the course and roll motion. Results show that the course performance can be tuned quantitatively to satisfy the different engineering requirements. For the combined system of the course and roll motion, it is found that the course control and roll stabilization performances conflict with each other due to their coupling. The adaptive robustness controllers can easily make a tradeoff between them due to a controller only with an adjustable parameter. Simulation shows that under the premise of the good course performance, the roll reduction rate (RRR) can decrease by nearly 32% through taking the rudder and propeller actions.