Uncertain Disturbance Attenuation and Rejection for Interval Type-2 Fuzzy Systems via Disturbance Observer

This study is concerned with the composite anti-disturbance issue for nonlinear systems subject to state saturation and parameter uncertainties, including the unknown harmonic disturbance. First, an interval type-2 (IT2) Takagi–Sugeno fuzzy model is proposed herein to describe the nonlinear system with state saturation and parametric uncertainties. Next, a novel disturbance observer framework is designed to eliminate the unknown harmonic disturbance. By introducing the new framework, the expression of the unknown harmonic disturbance is transformed into a new expression having only an uncertain parameter, which is then estimated. The corresponding composite anti-disturbance control scheme is then put forward and the sufficient conditions guaranteeing the stochastically stable of the composite system are established. Finally, the simulations are conducted to confirm the availability of the this control scheme.