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Station Keeping Capacity of a Moored Structure with Heading Control in Level Ice

Author(s): Li Zhou; Kaj Riska; Torgeir Moan

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Abstract: This paper deals with a simulation of heading control of a moored icebreaking tanker under level ice regime. A dynamic ice simulator interconnecting the vessel motions with the ice dynamics is used for the design of control system. In open water, the vessel with Dynamic Positioning (DP) is controlled to move in horizontal plane with surge, sway and yaw as required. This is not the case for DP in level ice. It is almost impossible to move a vessel to the side since the transverse ice load would be very large far being beyond the DP capacity. Therefore, the DP system needs to orientate the vessel to be always against the drifting ice with ship's ice breaking bow breaking the ice. In order to implement the station keeping operation at an appropriate position in level ice, yaw must be controlled by the DP system while surge and sway drift must be compensated by the mooring system. The moored tanker with heading control is simulated in the time domain. The corresponding results are analyzed in order to establish the effect of heading control on station keeping. It is found that the vessel with the heading control can be operated in more severe ice conditions than without DP control. Hence the operating season for moored ships can be extended.


Year: 2012

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