Sliding mode tracking control of an underactuated surface vessel

This study concerns the robust tracking control problem for an underactuated surface vessel with parameter uncertainties. In recent work by McNinch and collegeaues, a sliding mode control (SMC) law is presented and experimentally implemented for trajectory tracking of an underactuated autonomous surface vessel. The authors believe, however, their theory formulation involves essential flaws. Motivated by the obtained result by McNinch and collegeaues, a new revised SMC law is proposed under the same assumptions. The control law is similarly developed by introducing a first-order sliding surface in terms of surge tracking errors and a second-order surface in terms of lateral motion tracking errors; however, the desired surge and sway velocities are presented as a new form to guarantee the convergence of position tracking errors. Simulation results are provided to validate their method.