Saturated Adaptive Fuzzy Fixed-Time Nonsingular Integral Terminal Sliding-Mode Control of AUVs
针对自主水下航行器在动态不确定性、外部干扰及输入饱和下的轨迹跟踪问题，提出一种饱和自适应模糊固定时间非奇异积分终端滑模控制器，保证跟踪误差在固定时间内收敛到原点附近小邻域。
This article investigates the trajectory tracking control issue of autonomous underwater vehicles (AUVs) subject to dynamic uncertainties, external disturbances, and input amplitude and rate saturations. Initially, two new stable systems with fixed-time convergence are developed, and their upper bounds of settling time and convergence regions are thoroughly analyzed. Building on these systems, an enhanced fast nonsingular integral terminal sliding-mode (NITSM) surface and a new virtual control law are designed, respectively. Next, a novel saturated adaptive fuzzy fixed-time NITSM controller is proposed, circumventing the restrictions on uncertainties and input saturation in the existing results. The proposed controller ensures that the tracking error converges to a small neighborhood of the origin within a fixed time. Furthermore, to facilitate the adaptive fixed-time stability analysis, two new inequalities are established and rigorously proved. Using the two inequalities, the fixed-time stability of closed-loop systems is demonstrated by the Lyapunov's theory. Finally, representative numerical simulations validate the effectiveness of the proposed control scheme.