Functional Observer Design for T–S Fuzzy Systems With Complex Unmeasurable Premise Variables

This article is concerned with the problem of functional observer-controller (FOC) design when a complex unmeasurable premise variable (UPV) exists in the Takagi-Sugeno (T-S) fuzzy systems. Considering the nonlinearities in the UPV, a new transformation method is designed to linearize the premise variable (PV). Then, the PV could be estimated through the proposed FOC. The observer and controller gains are derived by deducing convex robust and stability conditions. Furthermore, a robust separation principle is utilized to make the estimate and control error system stable. Finally, simulation examples are provided to illustrate the effectiveness of the proposed method.