A 3DOF Path-Following Controller for a Non-Directionally Stable Vessel with Slow Thruster Dynamics

In this paper, a 3DOF path-following controller for an electric double-ended passenger ferry prototype is presented. The controller is formulated through a 3-step backstepping approach, taking into consideration several challenging physical properties of the vessel, such as a lack of passive damping in the vessel hull, lack of directional stability, and slow thruster dynamics compared to the vessel dynamics. The controller design also features a new thrust allocation approach that allows the thrust allocation of the over-actuated thruster system to be formulated on closed form, which enables us to include the thruster dynamics in the control law. The performance of the suggested 3DOF controller is demonstrated and compared to two other controllers through simulations with a model of the electric passenger ferry.