Model Predictive Control of Vessels with Azimuth Drives in Maneuvering Situations

Due to the worldwide increase in shipping traffic, the effort put in automation of ship motion control is also increasing. Despite great success in this area during the last decades, the maneuvering of ships with azimuth drives continues to be one of the most challenging tasks in ship motion control. To tackle this challenge, this paper presents a MPC (Model Predictive Control) based concept for controlling body-fixed velocities. To do so, a mathematical model is designed to describe the dynamics of a ship in a standardized form. Thereafter, a model predictive controller to control body-fixed velocities is developed. In order to deal with non-linearities resulting from the physical properties of the ships and their actuators, especially the azimuth drives, two configurations containing different restrictions are proposed. Thus, linear MPC techniques can be applied and input constraints are explicitly taken into account. Subsequently the controller is validated with simulations of different scenarios leaned on real maneuvers. The results obtained from the simulations show, that the designed concept leads to a functioning MPC approach for controlling body-fixed velocities. They also indicate that there are still some changes that have to be applied and research that has to be done before going about a real-life implementation.