Assisted Dynamic Positioning System for a FPSO Based on Minimization of a Cost Function

Abstract This paper presents a two-layer controller for a turret-moored FPSO. The first layer evaluates ship optimal heading, based on the minimization of a cost function relating important operational parameters, namely first-order roll oscillation, dynamic traction on risers, mooring lines offset and fuel consumption. Since this layer requires an estimate of the environmental conditions, it is proposed an indirect evaluation of the wave spectrum by the measurement of ship first-order oscillations. The second level receives the set point from the superior level and commands the thruster system. This layer is composed by a robust heading sliding-mode controller and the surge and sway motions are damped by a simple feedback linearization scheme. The controller was tested through numerical simulations of a moored VLCC under common environmental conditions found in Campos Basin, Brazil.