Robust adaptive path following for underactuated surface vessels with uncertain dynamics

A robust adaptive control strategy was developed to force an underactuated surface vessel to follow a reference path, despite the presence of uncertain parameters and unstructured uncertainties including exogenous disturbances and measurement noise. The reference path can be a curve or a straight line. The proposed controller was designed by using Lyapunov’s direct method and sliding mode control and backstepping techniques. Because the sway axis of the vessel was not directly actuated, two sliding surfaces were introduced, the first one in terms of the surge motion tracking errors and the second one for the yaw motion tracking errors. The adaptive control law guaranteed the uniform ultimate boundedness of the tracking errors. Numerical simulation results were provided to validate the effectiveness of the proposed controller for path following of underactuated surface vessels.