Nonlinear Vectorial Observer Backstepping with Integral Action and Wave Filtering for Ships

Abstract

In this paper a nonlinear control system for dynamic positioning and thruster assisted position mooring of ships is proposed. The control system is derived by using the observer backstepping design methodology. A nonlinear observer which provides wave filtering and bias state estimation from position and heading measurements is applied. Integral action is included in both the observer and controller to compensate for slowly-varying (constant) environmental disturbances. Stability is proven by applying Lyapunov stability theory.