Moving path following control for a surface vessel with error constraint

This paper discusses the moving path following control problem for a surface vessel with disturbances. The vessel is required to converge to and follow a desired geometric moving path while satisfying the tracking error without exceeding the prescribed constraint. A new barrier Lyapunov function is incorporated into the control algorithm to address the error constraint. Estimates of unknown disturbances are provided by nonlinear disturbance observers. An important feature of the proposed scheme is its versatility in being applicable to systems with or without constraints and with moving or stationary paths, without changing the control structure. It is demonstrated that all the signals in the closed-loop system are bounded under the proposed method while the prescribed bounds on the tracking errors will never be violated. This ensures the safety of the surface vessel and enhances the applicability of classical path following methods. The results of a further simulation demonstrate the effectiveness of the theoretical findings.