An auto weather-vaning system for a dp vessel that uses a nonlinear controller and a disturbance observer

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An auto weather-vaning system for a dp vessel that uses a nonlinear controller and a disturbance observer

Freier Zugriff

Kim Dae Hyuk / Kim Nakwan

An auto weather-vaning system for a Dynamic Positioning (DP) vessel is proposed. When a DP vessel is operating, its position keeping is hindered by ocean environmental disturbances which include the ocean current, wave and wind. Generally, most ocean vessels have a longitudinal length that is larger than the transverse width. The largest load acts on the DP vessel by ocean disturbances, when the disturbances are incoming in the transverse direction. Weather- vaning is the concept of making the heading angle of the DP vessel head toward (or sway from) the disturbance direc-tion. This enables the DP vessel to not only perform marine operations stably and safely, but also to maintain its posi-tion with minimum control forces (surge & sway components). To implement auto weather-vaning, a nonlinear control¬ler and a disturbance observer are used. The disturbance observer transforms a real plant to the nominal model without disturbance to enhance the control performance. And the nonlinear controller deals with the kinematic nonlinearity. The auto weather-vaning system is completed by adding a weather-vaning algorithm to disturbance based controller. Numerical simulations of a semi-submersible type vessel were performed for the validation. The results show that the proposed method enables a DP vessel to maintain its position with minimum control force.