Second-level sliding mode tracking control of unmanned surface vessels with parameter uncertainties

In this brief, we consider robust tracking control of an unmanned surface vessel in the presence of uncertainty associated with the hydrodynamic damping coefficients. A second-level sliding mode controller is proposed to force the considered ship to follow a reference path. To develop the controller, a pair of first-level sliding mode surfaces in terms of position tracking errors and velocity tracking errors is introduced. Then a second-level sliding mode surface is constructed based on the pair of first-level sliding mode surfaces. Simulation examples are included to demonstrate the effectiveness of the suggested approach.