Barrier-Function-Based Adaptive Sliding Mode Control for Path Following of USV With Unknown Disturbance

This paper addresses the path-following problem of an unmanned surface vehicle (USV) that must track a predefined path while maintaining a constant surge speed. To this end, the surge speed and yaw rate errors of the USV are formulated as sliding variables and a barrier function-based adaptive sliding mode controller is designed to ensure that the surge speed and yaw rate error converge within a predefined barrier. By incorporating a quasi–positive definite barrier function into the adaptation law, the proposed method mitigates the gain overestimation and the resulting chattering issues commonly observed in conventional adaptive sliding mode control. Unlike existing adaptive sliding mode control schemes, the proposed control strategy allows the convergence region and convergence time to be explicitly defined independently of the upper bound of disturbances, thereby preserving the sliding motion even when disturbances vary rapidly. Furthermore, the Lyapunov stability theory is employed to theoretically establish the finite-time stability of the closed-loop system. In addition, numerical simulations are conducted to verify the performance of the proposed controller.