Improving the combined operation of Dynamic Positioning and motion compensation from a control engineering perspective

The starting point of this research is to asses possible shortcomings of the combined operation of a Dynamic Positioning (DP) vessel and a motion compensation system, with respect to the amount of energy that is used. The motion compensation system is used to allow a safe transfer from the vessel to a static offshore structure. Both systems have the objective to track a fixed reference position. In the current situation these two systems are controlled independently, raising the idea that they could counteract each other. For a DP vessel operating on its own the ultimate goal is to track the reference position as close as possible using a reasonable amount of energy. However, for the combined operation the vessel just needs to stay close enough to the reference point so that the motion compensation system can do the rest. It is assumed that the latter needs less energy than the vessel to overpass the same distance. The goal of this thesis is to investigate options to adjust the existing or build a new DP controller containing a certain variable that can be used to make a trade-off. The maximum displacement of the vessel from the reference point can be weighed against the energy consumption. Simulation models of a DP vessel and of a motion compensation system are built in Simulink. Next to this, models for the energy consumption are derived for both systems. The proposed methods for energy consumption reduction are: using the integrated velocity as an estimation of the position of the vessel, the use of a reference circle instead of a reference point, the tuning of the thrust allocation optimization, and the use of Model Predictive Control (MPC). After Simulating two different scenarios it can be concluded that all methods yield energy consumption reductions, and taking into account some more preferences, overall MPC gives the best results.Mechanical, Maritime and Materials EngineeringDelft Center for Systems and ControlSystems & ControlSCP4530-4