On non-PDC local observers for TS fuzzy systems

In this paper we propose a method to design local observers for Takagi-Sugeno fuzzy models obtained from nonlinear systems by the sector nonlinearity approach. When a global observer cannot be designed, using our method it is still possible to design observers that are valid in a well-defined region of the state-space. The design is based on a nonquadratic Lyapunov function. Depending on whether or not the scheduling vector is a function of the states to be estimated, the conditions are formulated as an LMI or a BMI problem, respectively. The results are illustrated on simulation examples, for which classical observer design conditions are unfeasible.