Iranian journal of fuzzy systems
Volume:6 Issue: 1, Feb 2009

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

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 watershed 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. Extension property for (fuzzy) absorbent ordered filters is established. Conditions for (fuzzy) ordered filters to be (fuzzy) absorbent ordered fillters are provided. The notions of normal/maximal fuzzy absorbent ordered filters and complete absorbent ordered filters are introduced, and related 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 $(\in,\in,\vee q)$-fuzzy p-ideals, $(\in,\in,\vee q)$-fuzzy q-ideals and $(\in,\in,\vee q)$-fuzzy a-ideals in BCI-algebras and to investigate some of their related properties. Some characterization theorems of these generalized fuzzy ideals are derived. The relationship among these generalized fuzzy ideals of BCI-algebras is considered. It is shown that a fuzzy set of a BCI-algebra is an $(\in,\in,\vee q)$-fuzzy a-ideal if and only if it is both an $(\in,\in,\vee q)$-fuzzy p-ideal and an $(\in,\in,\vee q)$-fuzzy q-ideal. Finally, we consider the concept of implication-based fuzzy a-ideals in BCI-algebras, in particular, the implication operators in Lukasiewicz system of continuous-valued logic are discussed.