Abstract
In this study, the problem of robust control for nonlinear stochastic systems subject to time-varying parameter is treated by a proposed switching fuzzy stabilization scheme via output feedback. Switching multiple-modeling approach has been used to deal with linear systems with time-varying parameters or structure. Conventionally, Takagi-Sugeno (TS) fuzzy modeling method is usually adopted to approximate the nonlinear time-invariant systems, but not suitable for nonlinear time-varying systems. Combining the switching multiple-modeling approach and TS fuzzy modeling method, a robust fuzzy observer-based controller, based on the switching TS fuzzy model, is proposed for the stabilization of the nonlinear time-varying stochastic systems. In order to mitigate the model approximation error and external disturbance in the systems, the proposed H2/Hinf switching fuzzy observer-based control achieves H2 suboptimal control and Hinf attenuation of external disturbance simultaneously. The conditions for the existence of the proposed H2/Hinf switching fuzzy observer-based controller are provided in terms of linear matrix inequalities (LMIs), allowing the use of standard convex optimization procedures to solve the proposed robust H2/Hinf output control design problem for nonlinear time-varying stochastic systems. Finally, numerical simulations are provided to illustrate the design procedure and to confirm the performance of the proposed robust H2/Hinf switching fuzzy observer-based controller for nonlinear time-varying stochastic systems.