Speed-varying Path Following for Underactuated Marine Craft

In this paper, we study the path-following problem for marine craft which are unactuated in the sway dynamics. The proposed control law is derived using the method of least squares to find an approximate solution of overdetermined systems. The controller adjusts the speed according to the distance to the path and the rate of convergence while it stabilizes the unactuated dynamics. We show the circumstances under which the proposed controller achieves path following. The origin of the error dynamics is proven to be globally asymptotically and locally exponentially stable.