Performance Comparison Between Linear and Nonlinear Controllers for a Dynamic Positioning System

This paper addresses some preliminary discussion concerning the performance of different dynamic observer-controller-based positioning system for a shuttle tanker by considering her operational condition changes. The observer-controller models are nonlinear passivity based observer and backstepping controller, Extended Kalman Filter and Proportional-Derivative like controller, and notch filter and Proportional-Integral-Derivative controller. The variation of the operational condition of the vessel is obtained by changing the vessel draft and the environmental condition, such as relative incidence of the current, waves and wind, and the peak period of the sea wave spectrum. The performance of the dynamics of the vessel is investigated through numerical simulation in which a saturation model for the actuators is included. Preliminary results have indicated that the nonlinear observer-backstepping controller is the easiest approach to select the observer and control parameter in the case of variation of the draft.