A nonlinear path following controller for an underactuated unmanned surface vessel

This work presents a novel path following controller for underactuated unmanned surface vessels (USVs) that is both provably stable and intuitive to tune. The approach consists of a navigation component that computes a desired heading angle to ensure the USV will arrive at the path, and a nonlinear controller to guarantee exponential tracking of surge velocity and heading. Additionally, ultimate boundedness of the unactuated sway velocity is proven. Simulation results are presented to show numerically that the controller works as expected in the ideal case. Outdoor experimental results are presented, using a GPS and compass as sensors, showing the practical feasibility of the approach in the presence of sensor noise, disturbances, and unmodeled dynamics.