Composite Disturbance Observer-Based Adaptive Fuzzy Predefined-Time Control for Nontriangular State-Constrained Nonlinear Systems
针对带有状态约束和外部扰动的非三角非线性系统，提出了一种基于复合扰动观测器的自适应模糊预定时间控制方法，通过状态变换和预定时间滤波器处理约束与虚拟控制信号重复导数问题，确保状态在约束内且误差在预定时间内收敛。
In this work, the nonsingular predefined-time adaptive fuzzy control problem is investigated for uncertain nontriangular nonlinear systems with state constraints and mismatched external disturbances. First, a novel composite predefined-time disturbance observer is developed to accurately estimate the composite disturbance, including fuzzy approximation errors and unknown external disturbances. Second, a state transformation is implemented to deal with the state constraints by constructing a state dependent function, after which the restrictive feasibility condition is no longer required. Moreover, to eliminate the effect arising from the repeated derivatives of the virtual control signal, a predefined-time filter is embedded into the backstepping-based controller. Then, an event-triggered nonsingular predefined-time adaptive fuzzy control is developed by introducing hyperbolic tangent functions to ensure that all states remain within the constraints and the error signal can converge to an arbitrarily small region in a predefined time. Finally, simulation examples illustrate the validity of the presented theoretical method.