Robust path following of underactuated ships using Serret-Frenet frame

This paper develops a controller that forces an underactuated surface ship to follow a predefined path at a constant forward speed controlled by the main thruster system under the presence of environmental disturbances induced by wave, wind and ocean-current. The proposed controllers are designed using Lyapunov´s Direct Method. A new stability result for nonlinear cascade systems with non-vanishing uncertainties is introduced to analyze closed-loop stability.