LMI based fuzzy observer design for Takagi-Sugeno models containing vestigial nonlinear terms DUŠAN KROKAVEC and ANNA FILASOVÁ The paper deals with the problem of full order fuzzy observer design for the class of continuous-time nonlinear systems, represented by Takagi-Sugeno models containing vestigial nonlinear terms. On the basis of the Lyapunov stability criterion and the incremental quadratic inequalities, two design conditions for this kind of system model are outlined in the terms of linear matrix inequalities. A numerical example is given to illustrate the procedure and to validate the performances of the proposed approach.Key words: Takagi-Sugeno models, fuzzy observer, linear matrix inequality, incremental quadratic inequality
IntroductionAs is well known, observer design is a hot research field owing to its particular importance in the state-space control. The nonlinear system theory principles, using Lipschitz conditions, has emerged as a method capable of use in state estimation for nonlinear systems, although Lipschitz condition is a strong restrictive condition which many classes of systems may not satisfy. Design method for asymptotic observer for nonlinear systems with globally Lipschitz nonlinearities is presented, e.g., in [1], [4], [13], [22], the problem of designing asymptotic observers for the system whose nonlinear time-varying terms satisfy an incremental quadratic inequality, is given in [2], [3].An alternative to design an observer for nonlinear systems is fuzzy modeling approach, which benefits from the advantages of the approximation techniques approximating nonlinear system model equations [20]. Stability conditions, relying on the feasibility of an associated system of linear matrix inequalities (LMI) and Takagi-Sugeno (TS) fuzzy model based nonlinear state observers, were educed, e.g., in [11], [17], [19].