Graphical and numerical approach to robust stability analysis of fuzzy modeled systems with parametric uncertainty and disturbance

In this paper, robust stability analysis methods for the fuzzy feedback control systems are presented, the graphical method via multivariable circle criterion and the numerical method via linear matrix inequalities (LMI). The well-known Takagi-Sugeno fuzzy model is used as the nonlinear plant model. Uncertainties are assumed to be included in the model structure with known bounds. For these structured parametric uncertainties, L2 robust stability analysis is performed by taking external disturbance as input and system state as output. The effectiveness of the proposed methods is illustrated by examples.