Thruster-Assisted Position Mooring of C/S Inocean Cat I Drillship
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- Institutt for marin teknikk 
This thesis presents the development of a new research foundation into the Marine Cybernetic Laboratory, the C/S Inocean Cat I Drillship. This is a 1:90 scaled model of an Arctic drillship design by Inocean for Statoil. The C/S Inocean Cat I Drillship model is equipped with six Aero-naut Precision Schottel azimuth thrusters which are driven by six O.S. OMA-2820-950 motors and six Dynamixel MX-106R servo motors. To control the model a real time controller, CompactRIO, from National Instruments is used. The system is powered by six 12 V 12 Ah lead batteries. To make the hull durable and lightweight, it is constructed by carbon fiber and a casted frame stiffens the hull. The model has a detachable lidmade of Plexiglass, that secures the equipment inside from water. In order to design a thruster-assisted position mooring control system, a 6 DOF mathematical model of the scale model is needed. Equations for hydrodynamic modeling of marine vessels and mooring lines are presented, and combined to get the system equations. In addition, a 3 DOF mathematical model has been derived to verify other experiments. The scaled model is tested in the MC Lab, where real scaled conditions can be applied. The experiments show great results for the different controllers, and the vessel manages the different conditions. Comparison between the simulation model and the scale model is performed for all cases. The results yield that the simulation model needs further development to be more similar to the scale model, but it gives a good indication on the behavior of the vessel. The complete C/S Inocean Cat I Drillship is a fully functional vessel, and a stable research foundation to be used in further experiments in the MC Lab.