Adaptive Fuzzy SOSM Controller Design With Output Constraints

Abstract

The output constraints are widespread in physical systems. Violation of output constraints may result in system damage and performance degradation. This article investigates the design issue of adaptive fuzzy second-order sliding-mode (SOSM) controller, which aims to handle a class of nonlinear systems with output constraints. The unknown bounds of uncertainties are approached dynamically by fuzzy logic systems. Through designing a new barrier Lyapunov function, the output constraint problem has been well solved. Then, by integrating adding a power integrator technology and adaptive fuzzy control, a novel adaptive fuzzy SOSM controller is proposed. It is proved that the proposed method makes the output variable not violate the specified constraint region. At the same time, it can be shown, based upon the Lyapunov approach, that the finite-time stability of the resulting closed-loop system under output constraint is ensured. Finally, a numerical example and a practical pendulum system are presented to demonstrate the validity of the proposed SOSM control strategy.