NONLINEAR OUTPUT-FEEDBACK CONTROL OF DYNAMICALLY POSITIONED SHIPS USING VECTORIAL OBSERVER BACKSTEPPING

Dynamic positioning (DP) systems for ships are usually designed under the assumption that the kinematic equations can be linearized about a constant yaw angle such that linear theory and gain scheduling techniq ues can be applied. This paper proposes a globally exponentially stabl e (GES) nonlinear observer is included in the design such that only po sition measurements are required. GES is proven by applying the backst epping design methodology and Lyapunov stability theory. The control l aw is simulated on two thruster-controlled ships.