An underactuated unmanned surface vessel (USV) is a nonholonomic system, in which trajectory tracking is a challenging problem that has drawn more and more attention from researchers recently. The control of trajectory tracking is of critical importance since it determines whether the task can be carried out successfully. In this paper, a non-singular terminal sliding model (NTSM) controller is proposed for the trajectory tracking control of the underactuated USV, with a nonlinear disturbance observer which is designed to measure complex environmental disturbances such as wind, waves, and currents. Exploratory simulations were carried out and the results show that the proposed controller is effective and robust for the trajectory tracking of underactuated USVs in the presence of environmental disturbances.

This study is concerned with stability analysis for Takagi–Sugeno (T–S) fuzzy systems with time‐varying delay. By applying the idea of scalar function and augmented vectors, dealing with the positivity of a functional, a novel simple Lyapunov–Krasovskii functional is established. Then, fuzzy‐weighting dependent matrices and the reciprocally convex approach are introduced to deal with two integral parts, convex analysis approach is used to solve the useful terms (which are ignored in previous methods), with the above methods some less conservative stability criteria is obtained. Finally, three numerical examples are provided to show the effectiveness and improvements of the proposed conditions.

In order to approximate any nonlinear system, not just affine nonlinear systems, generalized T‐S fuzzy systems, where the control variables and the state variables, are all premise variables are introduced in the paper. Firstly, fuzzy spaces and rules were determined by using ant colony algorithm. Secondly, the state‐space model parameters are identified by using genetic algorithm. The simulation results show the effectiveness of the proposed algorithm.