A ROBUST NONLINEAR CONTROL DESIGN FOR PATH FOLLOWING OF A MARINE SURFACE VESSEL

Abstract

The problem of path following for marine surface vessels using rudder angle is addressed in this paper. A 4 degrees of freedom nonlinear surface vessel model, together with the Serret-Frenet equations, is introduced to describe the ship dynamics and path following error dynamics. While similar models have been used and reported in literature for path following control algorithm development, the novelty of the approach presented in this work lies in the following aspects: (a) The back-stepping nonlinear controller design is based on feedback dominance, instead of feedback linearization and nonlinearity cancellation; (b) Relying on feedback dominance, the resulting controller is almost linear, with very benign nonlinearities allowing for analysis and evaluation; (c) Performance of the nonlinear controller, in terms of path following, is analyzed for robustness in the presence of rudder saturation and rate limits, delays in the control execution, as well as measurement noises. Because of its simple form, very limited on-board computational power is required to implement the control. The simulation results are presented to verify and illustrate the analytic development and the effectiveness of the resulting control.