Iranian Journal of Fuzzy Systems
Year:2009 | Volume:6 | Issue:1|Papers Count:7

In this paper we consider the problem of delay-dependent robust H¥ control for uncertain fuzzy systems with time-varying delay. The Takagi- Sugeno (T-S) fuzzy model is used to describe such systems. Time-delay is assumed to have lower and upper bounds. Based on the Lyapunov-Krasovskii functional method, a sufficient condition for the existence of a robust H¥ controller is obtained. The fuzzy state feedback gains are derived by solving pertinent LMIs. The proposed method can avoid restrictions on the derivative of the time-varying delay assumed in previous works. The effectiveness of our method is demonstrated by a numerical example.

This paper will introduce a new method to obtain the order weights of the Ordered Weighted Averaging (OWA) operator. We will first show the relation between fuzzy quantifiers and neat OWA operators and then offer a new combination of them. Fuzzy quantifiers are applied for soft computing in modeling the optimism degree of the decision maker. In using neat operators, the ordering of the inputs is not needed resulting in better computation efficiency. The theoretical results will be illustrated in a water resources management problem. This case study shows that more sensitive decisions are obtained by using the new method.

The purpose of this study is to find the percentiles of fuzzy numbers and to demonstrate their applications, which include finding weighted means, dispersion indices, and the percentile intervals of fuzzy numbers. The crisp approximations of fuzzy numbers introduced in this paper are new and interesting for the comparison of fuzzy environments, such as a variety of economic, financial, and engineering systems control problems.

The notion of absorbent ordered filters in implicative semi groups is introduced, and its fuzzification is considered. Relations among (fuzzy) ordered filters, (fuzzy) absorbent ordered filters, and (fuzzy) positive implicative ordered filters are stated. The extension property for (fuzzy) absorbent ordered filters is established. Conditions for (fuzzy) ordered filters to be (fuzzy) absorbent ordered filters are provided. The notions of normal/maximal fuzzy absorbent ordered filters and complete absorbent ordered filters are introduced arid their properties are investigated.

Based on a complete Heyting algebra L, the relations between Lfuzzifying convergence spaces and L-fuzzifying topological spaces are studied. It is shown that, as a reflective subcategory, the category of L-fuzzifying topological spaces could be embedded in the category of L-fuzzifying convergence spaces and the latter is cartesian closed. Also the specialization L-preorder of L-fuzzifying convergence spaces and that of L-fuzzifying topological spaces are investigated.

The aim of this paper is to introduce the notions of (Î,ÎVq)- fuzzy p-ideals, (Î,Î Vq)-fuzzy q-ideals and (Î,ÎVq)-fuzzy a-ideals in BCI-algebras and to investigate some of their properties. Several characterization theorems for these generalized fuzzy ideals are proved and the relationship among these generalized fuzzy ideals of BCI-algebras is discussed. It is shown that a fuzzy set of a BCI-algebra is an (Î,ÎVq)-fuzzy a-ideal if and only if it is both an (Î,ÎVq)-fuzzy p-ideal and an (Î,ÎVq)-fuzzy q-ideal. Finally, the concept of implication-based fuzzy a-ideals in BCI-aigebras is introduced and, in particular, the implication operators in Lukasiewicz system of continuous valued logic are discussed.