Dynamic Positioning in Ice: Comparison of Control Laws in Open Water and Ice

Dynamic Positioning (DP) systems are intensely used in a large range of ship operations nowadays. The growing interest of Arctic exploration and exploitation may introduce a new application area for those systems. The very few full scale DP operations in the Arctic have demonstrated the need for improvements in DP systems for ice-covered waters. External forces due to the ice environment are very different from open water forces and especially the dynamic component of the loads is much higher. This paper firstly reviews DP in open water and spotlights the needs for adaptations to ice-covered regions. The architecture of a controller answering ice requirements is then presented. This system has been successfully tested at the large ice tank of the Hamburg Ship Model Basin (HSVA) in 2012 within the European R&D project DYPIC [1]. The designs of open water and ice control laws are then compared in two simulation frameworks. The first framework involves only the current, wind and waves, while the second framework deals with the ice conditions. The numerical ice simulator, utilized in this paper, is a novel high-fidelity modelling tool developed by the Norwegian University of Science and Technology (NTNU).