Sliding mode based path following nonlinear control for underactuated surface vessels

A sliding mode control law is presented for designing a path following controller that forces an underactuated surface vessel to follow a reference path. The reference path can be a prescribed path or one generated by a virtual vessel. The control law is developed by using Lyapunov direct method and sliding mode control. According to that the sway axis of the vessel is not directly actuated, and the damping matrixes are off-diagonal, two second-order sliding surfaces are introduced, the first surface in terms of path tracking position errors and the second one in terms of orientation errors. Numerical simulation results are provided to demonstrate the effectiveness of the proposed controller design and the accuracy of stability analysis.