A simple output-feedback control for trajectory tracking of underactuated surface vessels

This paper proposes an output-feedback control method for the tracking, of underactuated surface vessels (USVs) with actuator saturations. The proposed scheme is designed using a predefined performance function that can make the structure of the control system to be simple. Unlike previous methods based on a predefined performance function, the proposed observer does not use an adaptive or intelligent technique to compensate for model uncertainties and external disturbances. To this end, observer errors are newly proposed. In the controller design, auxiliary variables are developed to deal with the underactuated and input saturation problems of USVs. Furthermore, the approach angle is used to track all types of trajectories. Finally, the semi global boundedness of the proposed scheme is proved using the Lyapunov stability theory.