Dynamic positioning of a turret moored FPSO using sliding mode control

This paper presents the application of a sliding mode control technique to the dynamic positioning of a turret moored FPSO. The proposed controller is robust with respect to modelling errors and variations in the intensity an d direction of environmental forces. Since the system is strongly non-linea r, the sliding mode methodology is appropriate because it does not require linearization and uses the complete model for the controller design. Furthe rmore, the design of the controller term that guarantees robustness is very simple, and can be generalized to any adopted model of dynamic and environ mental forces. The main drawback of the sliding controller, related to the high oscillatory control action, is avoided by the definition of a "boundar y layer" near the sliding surface. The controller was tested through numeri cal simulations of a moored VLCC under several environmental conditions, co nfirming the stability and performance robustness. Copyright (C) 2001 John Wiley & Sons, Ltd.