Thruster-Assisted Position Mooring of a Turret-Moored FPSO Using Sliding Mode Controller and Model-Based Observer

This paper deals with designing a control system for a thruster-assisted position mooring of a turret-moored FPSO. For this, a sliding mode controller is designed for an FPSO to compensate for environmental disturbances due to wind, waves and ocean currents and to account for the uncertainties. For wave-filtering and state estimation, a new approach is utilized which is a combination of a notch filter and a model-based observer. The filter is used to obtain the low-frequency motion of the FPSO and the observer is responsible for estimating velocities and environmental disturbances. Via simulation studies, it is shown that the proposed control system decreases the positioning error significantly compared to mooring system and de-creases the forces acting upon the mooring lines which in turn increases the safety of mooring lines.

Keywords:

Dynamic Positioning , Model-based Observer , Environmental disturbances , Sliding Mode Control , Turret-moored FPSO