Control and Simulation of a Thruster-Assisted Moored Offshore Vessel in Sea-ice
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- Institutt for marin teknikk 
The exploration of the northern seas is constantly raising new and interestingresearch topics in order to adapt our technology to handle this extraordinaryharsh climate. Darkness, remoteness, cold and harsh weather, and not at least,drifting ice and icebergs, are making the conventional equipment used furthersouth useless. The ice loads are largely different from open water sea loads, whileremoteness and the harsh environment makes safety an even more important issue.The Arctic conditions are difficult to recreate due to the inpredictability andlarge variations in ice features, and going up there with all the needed equipmentis particularly expensive. It is possible to create realistic ice features in a modelbasin, but it takes time and effort compared to open water.This is why a numerical computer simulator is an attractive option. Thisthesis is investigating the properties of the Numerical Ice Tank (NIT) simulatordeveloped at NTNU in order to implement a high fidelity turret mooring modelinto it. A finite element based mooring model is implemented and tested in theNIT. Controller strategies for adaption into ice infested areas are discussed andtested in the simulator.A theoretical background on dynamic positioning (DP), position mooring(PM), controller design, arctic conditions and mathematical modelling is pro-vided.