Robust path-following control of a container ship based on Serret–Frenet frame transformation

A novel disturbance observer-based backstepping controller (DOBBC) is developed and applied to the path-following system of a container ship. Our control objective is to enable the ships to follow a desired path despite the presence of environmental disturbances caused by current, wind, and wave actions. It is particularly challenging to achieve such an objective due to the underactuation and nonlinearity of container ships. To simplify controller design, a tracking error model is developed based on Serret–Frenet frame transformation. The proposed path-following control system is constructed on the model. In DOBBC, the disturbance observer estimates both constant and time-variant environmental disturbances. The backstepping controller compensates the nonlinearity and underactuation of the container ship. A feedback-dominance technique is utilized to design the controller parameters. The stability and robustness of the control system are successfully justified through Lyapunov approach. Simulation results demonstrate that the DOBBC effectively drives the ship to follow a desired trajectory in spite of the existence of time-varying environmental disturbances.