Applied Mathematical Sciences, Vol. 4, 2010, no. 70, 3493 - 3502
Fuzzy Integer Linear Programming with Fuzzy Decision Variables
C. Sudhagar1
Department of Mathematics and Applied Sciences Middle East College of Information Technology, Muscat, Oman [email protected]
K. Ganesan
Department of Mathematics, SRM University, Chennai, India gansan [email protected]
Abstract
In this paper a new method for dealing with Fuzzy Integer Linear Programming Problems (FILPP) has been proposed. FILPP with fuzzy variables model was taken for solution. This solution method is based on the fuzzy ranking method. The proposed method can serve deci- sion makers by providing the reasonable range of values for the fuzzy variable, which is comparatively better than the currently available solu- tions. Numerical examples demonstrate the effectiveness and accuracy of the proposed method.
Mathematics Subject Classification: 65K05, 90C10, 90C70, 90C90
Keywords: Fuzzy numbers, Ranking, Fuzzy integer linear programming
1 Introduction
Linear Programming Problems(LPP) have an outstanding relevance in the field of Decision making, Artificial intelligence, Control theory, Management sciences, Job placement interventions etc. In many practical applications the available information in the system under consideration are not precise. In such situations, it is more appropriate to use the fuzzy LPP.
1Corresponding author 3494 C. Sudhagar and K. Ganesan
The concept of fuzzy linear programming problems was first introduced by Tanaka et al.,[13, 12] After his work, several kinds of fuzzy linear programming problems have appeared in the literature and different methods have been proposed to solve such problems. Numerous methods for comparison of fuzzy numbers have been suggested in the literature.
In Campos Verdegay paper[2] linear programming problems with fuzzy constraints and fuzzy coefficients in both matrix and right hand side of the constraint set are considered. Herrera and Verdegay[4] have proposed three methods for solving three models of FILPP based on the representation theo- rem and on fuzzy number ranking. Maleki, Tata and Mashinchi[5, 6] used the Rouben[10] method of comparison of fuzzy numbers and obtained an optimal solution. Nasseri [8] has proposed a different method for solving the fuzzy linear programming problems in which he has used the ranking method for converting the fuzzy objective function into crisp objective function.
Allahviranloo et al.,[1] discussed a model of FILPP with fuzzy variable and proposed a new method for solving. They considered the right hand side (RHS) coefficients of the constraints as symmetric triangular fuzzy number and used the ranking method to solve it. Pandian et al.,[9] have proposed a decomposi- tion method for solving FILPP with fuzzy variables by using classical integer linear programming. In general the authors have restricted to triangular or trapezoidal fuzzy numbers for modeling the FILPP.
In this paper we consider the FILPP with fuzzy variables and fuzzy RHS. The RHS fuzzy coefficients of the constraints can be of triangular, trapezoidal or LR type. A new method for solving this model by using the ranking pa- rameters is proposed. These ranking parameters are used to rank any set of fuzzy numbers in our earlier paper[11].
The rest of the paper is organized as follows. In section 2 definitions of fuzzy membership function, fuzzy integer, ranking parameters of a fuzzy num- ber, ranking methods, FILPP with fuzzy variables and fuzzy RHS model are discussed. In section 3, we propose a new method to solve FILPP with fuzzy variables and fuzzy right hand side. In section 4, the proposed ranking method is illustrated with suitable examples and compared with the existing methods. The conclusions and acknowledgements are given in Section 5.
2 Preliminaries
In this section the basic concepts of fuzzy membership function, fuzzy number, fuzzy integer, ranking parameters, ranking methods, FILPP model are given. FILPP with fuzzy decision variables 3495
Definition 2.1 A fuzzy number is a fuzzy subset of the real line R which is convex and normal. Let F be the set of all fuzzy numbers which are upper semi continuous and have compact support. The support of a fuzzy number a˜ ˜ → with membership function fki : R [0, 1] is denoted by supp(a˜)=[la,ra] ⎧ ⎪ ˜ a ≤ ≤ ⎪ fkl (t) l t a ⎨⎪ 1 a ≤ t ≤ a fk˜ (t)= (1) i ⎪ f˜ (t) a ≤ t ≤ ra ⎩⎪ kr 0 otherwise.
Definition 2.2 A fuzzy integer I˜ will have discrete membership function defined as follows:
µ1 µr 1 µr+2 µ2r+1 I˜ = { , ..., , , , ...., }, (2) n − r n − 1 n n +1 n + r where n is an integer, r can be 1,2,3,..... and 0 <µ1 <µ2 < ..... < µr < 1, 1 >µr+2 > .... > µ2r+1 > 0.
Definition 2.3 Consider the fuzzy number A˜i and its member ship function ˜ ˜ fAi . If the membership function fAi is a continuous or piecewise continuous function defined in an interval [a,b] then the mean parameter Si and spread parameter Ti of the fuzzy number are given by