Composite Disturbance Observer-Based Adaptive Fuzzy Predefined-Time Control for Nontriangular State-Constrained Nonlinear Systems
Wei Wei, Tianliang Zhang, Weihai Zhang
Abstract
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.