NDLI: Modeling, Parameter Identification and Thruster-Assisted Position Mooring of C/S Inocean Cat I Drillship

Content Provider	The American Society of Mechanical Engineers (ASME) Digital Collection
Author	Bjørnø, Jon Heyn, Hans-Martin Skjetne, Roger Andreas, R. Dahl Frederich, Preben
Copyright Year	2017
Abstract	A thruster-assisted position mooring (TAPM) system includes different control functions for stationkeeping and motion damping for a moored offshore vessel with assist from thrusters. It consists of a conventional mooring system and a dynamic positioning (DP) system. The thrusters are used to provide damping and some restoring to the vessel motion and compensate if line breakage occurs. The mooring system absorbs the main loads to keep the vessel in place. This paper presents a complete modeling, parameter identification, and control design for a 1:90 scaled TAPM model vessel. The numerical values for the different model parameters are identified from towing tests. State-of-the-art TAPM control algorithms have been tested on the vessel in the Marine Control Laboratory (MC Lab), to see the behavior resulting from the different control algorithms. The presented experiments focus on the setpoint chasing algorithm, where the position setpoint slowly moves to the equilibrium position where the environmental loads are balanced by the mooring loads. This avoids conflicts between the mooring system and the control actions. If the environmental loads are too large so that the setpoint exceeds a user-defined safety radius, the setpoint is set to this radius and thruster forces grow to support the mooring system in counteracting the environmental loads to avoid line breakage. The experiments show that the vessel and setpoint chasing control algorithm behaves as expected, minimizing thruster usage and maximizing utilization of mooring system.
Sponsorship	Ocean, Offshore and Arctic Engineering Division
File Format	PDF
ISBN	9780791857748
DOI	10.1115/OMAE2017-61896
Volume Number	Volume 7B: Ocean Engineering
Conference Proceedings	ASME 2017 36th International Conference on Ocean, Offshore and Arctic Engineering
Language	English
Publisher Date	2017-06-25
Publisher Place	Trondheim, Norway
Access Restriction	Subscribed
Subject Keyword	Damping Mooring Vessels Equilibrium (physics) Modeling Stress Design Algorithms Drillships Control algorithms Dynamic positioning systems Ocean engineering Safety
Content Type	Text
Resource Type	Article

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