Journal of Intelligent & Fuzzy Systems - Volume 19, issue 2

Authors: Tong, Shaocheng | Shi, Peng | Al-Madfai, Hasan

Article Type: Research Article

Abstract: This paper addresses the problem of robust fuzzy decentralized control for a class of nonlinear large-scale systems in the presence of parametric uncertainties. The Takagi-Sugeno (T-S) fuzzy system is adopted for modeling such systems. Both fuzzy state feedback decentralized controller and fuzzy observer-based decentralized controller are developed. Sufficient conditions are derived for robust stabilization in the sense of Lyapunov asymptotic stability and formulated in the format of linear matrix inequalities (LMIs). The …effectiveness of the proposed fuzzy controller is finally demonstrated through numerical simulations on a two-machine interconnected system. Show more

Keywords: Fuzzy large-scale systems, fuzzy observer, fuzzy control, robust stability

Citation: Journal of Intelligent & Fuzzy Systems, vol. 19, no. 2, pp. 85-101, 2008

Authors: Juang, Chia-Feng

Article Type: Research Article

Abstract: This paper proposes a Symbiotic Genetic Algorithm with Local-and-Global mapping search (SGA-LG) for fuzzy controller design under reinforcement learning environments. The objective of the proposed SGA-LG is to increase the reinforcement fuzzy controller design efficacy and efficiency. SGA-LG operates in two concurrently evolving searches: the local mapping search and the global mapping search. The local-mapping search helps to find the well-performed local rules. A population is created in this search, and each …individual in the population encodes only one fuzzy rule. An elite strategy is adopted, where the top-half best-performing individuals, the elites, are reproduced directly to the next generation, and parents are selected from the elites only. For global-mapping search, another population is created, where each individual encodes a whole fuzzy network as opposed to a single rule. The objective is to determine which local rules designed in the local-mapping search should be combined together to achieve a good fuzzy network. To demonstrate the performance of SGA-LG, it is applied to cart-pole and ball-and-beam system controls. The efficacy and efficiency of SGA-LG are verified by comparing with other GAs, evolution strategy and evolutionary programming based fuzzy controller designs. Show more

Keywords: Genetic fuzzy control, reinforcement learning, symbiotic evolution, coevolutionary computation, elite strategy

Citation: Journal of Intelligent & Fuzzy Systems, vol. 19, no. 2, pp. 103-114, 2008

Authors: Ganjigatti, J.P. | Pratihar, Dilip Kumar

Article Type: Research Article

Abstract: Metal inert gas welding is a multi-input and multi-output process. In forward modeling, the outputs (also known as the responses) are expressed as the functions of input variables (also called the process parameters), whereas in reverse modeling, the latter are represented as the functions of the former. The above modeling may be required for an effective on-line control of a process. Statistical regression analysis can tackle the problem of forward modeling efficiently but it may not …be always able to solve the problem of reverse modeling. The present work is a novel attempt to carry out the forward and reverse modeling of the said welding process using fuzzy logic-based approaches. The developed soft computing-based approaches are found to solve the above problem efficiently. Show more

Keywords: MIG welding, forward modeling, reverse modeling, fuzzy logic, genetic algorithm

Citation: Journal of Intelligent & Fuzzy Systems, vol. 19, no. 2, pp. 115-130, 2008

Authors: Eshghi, Kourosh | Nematian, Javad

Article Type: Research Article

Abstract: In this paper, we will discuss two special classes of mathematical programming models with fuzzy random variables. In the first model, a linear programming problem with fuzzy decision variables and fuzzy random coefficients is introduced. Then an algorithm is developed to solve the model based on fuzzy optimization method and fuzzy ranking method. In the second model, a fuzzy random quadratic spanning tree problem is presented. Then the proposed problem is formulated and solved by using …the scalar expected value of fuzzy random variables. Furthermore, illustrative numerical examples are also given to clarify the methods discussed in this paper. Show more

Keywords: Fuzzy random theory, fuzzy random linear programming, quadratic minimum spanning tree

Citation: Journal of Intelligent & Fuzzy Systems, vol. 19, no. 2, pp. 131-140, 2008

Authors: Ameri, R.

Article Type: Research Article

Abstract: In this paper we introduce fuzzy congruence and fuzzy strong congruence of semi-hypergroups as well as polygroups. We obtain some results in this respect. We also prove that FC(H), the set of all fuzzy strong congruences on a polygroup H, consists a complete lattice and this lattice is isomorphic to FN(H), the lattice of fuzzy normal subpolygroups.

Keywords: Semi-hypergroup, polygroup, fuzzy similarity relation, fuzzy compatible, fuzzy congruence, fuzzy strong congruence, fuzzy normal sub-polygroups

Citation: Journal of Intelligent & Fuzzy Systems, vol. 19, no. 2, pp. 141-149, 2008

Authors: Mateou, N.H. | Andreou, A.S.

Article Type: Research Article

Abstract: This paper focuses on developing Intelligent Decision Support Systems within the framework of Genetically Evolved Fuzzy Cognitive Maps, thus at modelling real world problems and supporting the decision making process. The proposed framework is based on encoding experts' assessments on the nature of the problem under consideration. This assessment is inputted in a fuzzy knowledge base that uses a linguistic form following which it is modelled and processed by means of Fuzzy Cognitive Maps. The optimisation …that follows with the help of Genetic Algorithms facilitates the simulation of hypothetical scenarios, while the defuzzification process implemented interprets the results along human reasoning lines. The effectiveness and reliability of the method proposed has been demonstrated by means of a case study on the Cyprus issue shortly before the April, 24 referendum. Show more

Keywords: Decision support systems, expert systems, fuzzy cognitive maps, genetic algorithms

Citation: Journal of Intelligent & Fuzzy Systems, vol. 19, no. 2, pp. 151-170, 2008