Multi – Objective Two Stage Fuzzy Transportation Problem with Hexagonal Fuzzy Numbers Using Fuzzy Geometric Programming

Dr. M. S. Annie Christi. Int. Journal of Engineering Research and Application www.ijera.com
ISSN : 2248-9622, Vol. 7, Issue 1, ( Part -5) January 2017, pp.23-29
www.ijera.com 23 | P a g e
Multi – Objective Two Stage Fuzzy Transportation Problem with
Hexagonal Fuzzy Numbers Using Fuzzy Geometric Programming
Dr. M. S. Annie Christi1
, Sumitha Devi2
1
Associate Professor, Department of Mathematics,Providence College for Women, Coonoor, India.
2
Department of Mathematics, Providence College for Women, Coonoor, India.
ABSTRACT
Fuzzy geometric programming approach is used to determine the optimal solution of a multi-objective two stage
fuzzy transportation problem in which supplies, demands are hexagonal fuzzy numbers and fuzzy membership
of the objective function is defined. This paper aims to find out the best compromise solution among the set of
feasible solutions for the multi-objective two stage transportation problem. To illustrate the proposed method,
example is used.
Keywords: Transportation problem, Hexagonal fuzzy numbers, two stage fuzzy transportation problem, Multi-
objective.
I. INTRODUCTION
Transportation models provide a powerful
framework to meet this challenge. They ensure the
efficient movement and timely availability of raw
materials and finished goods. Transportation
problem is a linear programming problem stemmed
from a network structure consisting of a finite
number of nodes and arcs attached to them. In a
typical problem a production is to be transported
from m sources to n destinations and their
capacities are a1 , a2 ,...am and b1,b2 ...bn ,
respectively. In addition there is a penalty Cij
associated with transporting unit of production
from source i to destination j. This penalty may be
cost or delivery time or safety of delivery etc. A
variable X ij represents the unknown quantity to be
shipped from source i to destination j. In general
the real life problems are modeled with multi-
objectives, which are measured in different scales
and at the same time in conflict. In some
circumstances due to storage constraints
designations are unable to receive the quantity in
excess of their minimum demand. After consuming
parts of whole of this initial shipment they are
prepared to receive the excess quantity in the
second stage. According to Sonia and Rita
Malhotra [23] in such situations the product
transported to the destination has two stages. Just
enough of the product is shipped in stage I so that
the minimum requirements of the destinations are
satisfied and having done this the surplus quantities
(if any) at the sources is shipped to the destinations
according to cost consideration. In both the stages
the transportation of the product from sources to
the destination is done in parallel. Efficient
algorithms [21] have been developed for solving
the transportation problem when the cost
coefficients and the supply and demand quantities
are known exactly. However, there are cases that
these parameters may not be presented in a precise
manner. For example, the unit shipping cost may
vary in a time frame. The supplies and demands
may be uncertain due to some uncontrollable
factors.
To deal quantitatively with imprecise
information in making decisions, Bellman and
Zadeh [2] and Zadeh [28] introduce the notion of
fuzziness. Since the transportation problem is
essentially a linear program, one straightforward
idea is to apply the existing fuzzy linear
programming techniques [4, 5, 9, 10, 15, 19, 24] to
the fuzzy transportation problem. Unfortunately,
most of the existing techniques [4, 5, 9, 10, 24]
only provide crisp solutions. The method of Julien
[10] and Parra et al. [19] is able to find the
possibility distribution of the objective value
provided all the inequality constraints are of „„≤‟‟
type or „„≥‟‟ type. However, due to the structure of
the transportation problem, in some cases their
method requires the refinement of the problem
parameters to be able to derive the bounds of the
objective value. There are also studies discussing
the fuzzy transportation problem [14]. Chanas et al.
[7] investigate the transportation problem with
fuzzy supplies and demands and solve them via the
parametric programming technique in terms of the
Bellman–Zadeh [2] criterion. Their method is to
derive the solution which simultaneously satisfies
the constraints and the goal to a maximal degree.
Chanas and Kuchta [6] discuss the type of
transportation problems with fuzzy cost
coefficients and transform the problem to a bi-
criterial transportation problem with crisp objective
function. Their method is able to determine the
RESEARCH ARTICLE OPEN ACCESS

efficient solutions of the transformed problem;
nevertheless, only crisp solutions are provided.
Verma et al. [25] apply the fuzzy programming
technique with hyperbolic and exponential
membership functions to solve a multi-objective
transportation problem [26], the solution derived is
a compromise solution. Similar to the method of
Chanas and Kuchta [6], only crisp solutions are
provided. Obviously, when the cost coefficients or
the supply and demand quantities are fuzzy
numbers, the total transportation cost will be fuzzy
as well.
In this paper two stage fuzzy
transportation problems [17] is discussed with
multi- objective constraints where the supply and
demand is hexagonal fuzzy numbers. This paper
aims to find out the best compromise solution
among the set of feasible solutions for the multi-
objective two stage transportation problem. Finally,
some conclusions are drawn from the discussions.
A numerical illustration is given to check the
validity of the proposed method.
II. PRELIMINARIES
2.1. Definition: Fuzzy Number:
A fuzzy number [31] is a convex
normalized fuzzy set on the real line R such that
there exists at least one x∈ R with
2.2. Definition: Triangular Fuzzy Number:
A fuzzy number is a TFN [11] denoted by =
( ) where real numbers and
its membership function are given below:
2.3. Definition: Trapezoidal Fuzzy Number:
A fuzzy number is a TrFN [1] denoted by =
( ) where real
numbers and its membership function are given
below:
2.4. Definition: Hexagonal Fuzzy Number:
A fuzzy number is a HFN [20] denoted by =
( ) where
real numbers and its
membership function are given below:
2.5. Definition: Arithmetic operations on
Hexagonal Fuzzy Number:
If = ( ) and =
( ) are two HFN‟s then the
following three operations can be performed as
follows:
 Addition:
(
)
 Subtraction:
(
)
 Multiplication:
(
)
2.6. Definition: Robust’s Ranking Techniques:
Robust‟s ranking technique [16] which satisfy
compensation, linearity and additive properties and
provides results which are consistent with human
intuition. If ã is a fuzzy number then the Robust‟s
ranking index is defined by R (ā)
= ) d where ( ) is the cut
of a fuzzy number a͂ .
Where ( ) = ((b-a) +a, d-(d-c) , (d-c) +c,
f-(f-e) ).
2.7. Definition: Compromise solution:
A feasible Vector [12] X*∈ S is called a
compromise solution of iff x*∈ E and
F( ) F(X ) where ^ stands for „minimum‟
and E is the set of feasible solutions.
III. FUZZY PROGRAMMING
APPROACH FOR SOLVING

MULTI-OBJECTIVE TWO STAGE
FUZZY
Transportation Problem (MOTSFTP): [22]
The minimum fuzzy requirement of a
homogeneous product at the Destination j is
denoted by and the fuzzy availability of the same
at source i is denoted by . Let
(x)={F1
(x),F2
(x),……Fk
(x)} be a vector of K
objective functions and the superscript on both
Fk
(x) and cijk
are used to identify the number of
objective functions k=1,2,3, k. Assume ai > 0 ∀ i,
bj > 0 ∀j, cijk
>=0 ∀ i,j and = . In stage-I
the Multi –objective Two-stage fuzzy Cost
Minimization Transportation Problem deals with
supplying the destinations their minimum
requirements and in stage-II the
quantity = is supplied to the destinations
from the sources which have surplus quantity left
after the completion of stage-I.
The stage-I problem can be formulated as
below:
Min Fk
(x) =
(1)
Where the set S1 is given by
S1=
x ij ≥ 0,∀ (i, j) , corresponding to a feasible solution
X = (xij) of the stage-I problem, the set
S2 = { = (xij)} of feasible solution of the stage-
II problem is given by
S2=
xij ≥ 0,∀ (i j) , where is the quantity available at
the ith
source on completion so the stage-I, that is
. Clearly
.
Thus the state-II problem would be mathematically
formulated as:
min Fk
(x) =
(2)
The feasible solution X =(X ij) of the stage-I
problem corresponding to which the optimal cost
for stage-II is such that the sum of the shipment is
the least. The Multi-objective two stage fuzzy cost
minimizing transportation problem [8] can,
therefore, be stated as,
min Fk
(x) =
(3)
Also from a feasible solution of the problem (3)
can be obtained. Further the problem (3) can be
solved by solving following fuzzy cost minimizing
Transportation problem
P1: min Fk
(x) =
(4)
where S2, the set of feasible solutions of (3), is
defined as follows
S2 =
X ij ≥ 0∀ (i, j)
where , and , represent fuzzy
parameters involved in the constraints with their
membership functions for a certain degree α
together with the concept of α level set [13] of the
fuzzy numbers . Therefore the problem of
Two stage MOFCMTP can be understood as
following non fuzzy α -general Two stage
transportation problem (α -two stage MOFCMTP).
S =
A point X*∈ X is said to be α -optimal
solution (α -Two stage
FCMTP), if and only if there does not exist another
x, y x (a,b), such that
Cij with strict inequality holding for
the at least one [6]
The problem (α -Two stage MOFCMTP) can be re
written in the following equivalent form (α′-Two
stage MOFCMTP)
S =
xij ≥ 0 ∀ i, j
The constraint (ai, bj L has been
replaced by the Constraint and
where
are lower and upper
bounds and ai, bj are constants. [9]
The parametric study [18] of the problem (α ' - Two
stage MOFCMTP) where and are
assumed to be parameters rather than constants and

(renamed hi, Hi and hj, Hj) can be understood as
follows.
Let X (h, H) denotes the decision space of problem
(α ' - Two Stage MOFCMTP), defined by
X (h, H) = (xij, ai, bj) –
, – -
ai - hi bj -
hj
IV. SOLUTION ALGORITHM [22]
Step 1: Construct the Transportation problem
Step 2: Supply and demand are hexagonal fuzzy
numbers (a1, a2, a3, a4, a5, a6) and (b1, b2, b3, b4, b5,
b6) respectively in the formulation problem (Two
Stage MOFCMTP).
Step 3: Convert the problem (α -Two Stage
MOFCMTP) in the form of the problem (α ' - Two
stage MOFCMTP)
Step 4: Formulate the problem (α ' - Two stage
FCMTP) in the parametric form.
Step 5: Apply VAM to get the basic feasible
solution.
V. VOGEL APPROXIMATION
METHOD: (VAM)
VAM is an improved version of the least cost
method that generally, but not always, produces
better starting solutions.
Step 1: For each row (column), determine a
penalty measure by subtracting the smallest unit
cost element in the row (column) from the next
smallest unit cost element in the same row
(column).
Step 2: Identify the row or column with the largest
penalty. Break ties arbitrarily. Allocate as much as
possible to the variable with the least unit cost in
the selected row or column. Adjust the supply and
demand, and cross out the satisfied row or column.
If a row and a column are satisfied simultaneously,
only one of the two is crossed out, and the
remaining row (column) is assigned zero supply
(demand).
Step 3:
(a). If exactly one row or column with zero supply
or demand remains uncrossed out, stop.
(b). If one row (column) with positive supply
(demand) remains uncrossed out, determine the
basic variables in the row (column) by the least
cost method. Stop.
(c). If all the uncrossed out rows and columns have
(remaining) zero supply and demand, determine the
zero basic variables by the least cost method. Stop.
(d). Otherwise, go to step 1.
VI. GEOMETRIC PROGRAMMING
APPROACH FOR SOLVING MOTP
In 1970, Bellman and Zadeh [2]
introduced three basic concepts; fuzzy goal (G),
fuzzy constraints (C), and fuzzy decision (D) and
explored the applications of these concepts to
decision making under fuzziness. The fuzzy
decision is defined by,
D = G ∩ C
This problem is characterized by the membership
functions [27]:
μD (x) = min (μG (x), μC (x))
let Lk ,Uk be the lower and upper bounds
of the objective functions F k
(x). To define the
membership function of MOTP problem, these
values are determined as follows: consider a single
objective transportation problem in that the
individual minimum of each objective function
subject to the given set of constraints are
calculated. The optimal solutions for the K
different transportation problems is given by X 1
, X
2
,....X k
. Evaluate each objective function at all
these k optimal solutions. Assume that at least two
of these solutions are different for which the kth
objective function has different bounded values.
Find the lower bound (minimum value) Lk and the
upper bound (maximum value) U k for each
objective function F k
(x). On the basis of
definitions L k and k U k, Biswal [3] gives a
membership function of a multi-objective
geometric programming problem which can be
implemented for the MOTP problem as follows:
Uk Fk
(x) =
where Lk ≠Uk , k = 1,2,....,k. If Lk=U k then μ k (F
k
(x)) = 1
for any value of k.
Following the fuzzy decision of Bellman and
Zadeh [2] together with the linear membership
function (5), a fuzzy optimization model of MOTP
problem can be written as follows.
P2 : Max

Subject to
i = 1, 2... m
j = 1, 2... n
By introducing an auxiliary variable β , problem P2
can be transformed into the following equivalent
conventional linear programming (LP) problem
[30].
P3 : Max β
Subject to
β ≤ μ k(F k
(x)) , k = 1,2,...k
0 ≤ β ≤ 1,
∀ i, j
In problem P3, constraint (1) can be reduced to the
following form.
β (U k - L k ) (U k - F k
(x)),
β (U k - L k ) + F k
(x) U k
β (U k - L k )/ U k+ (1/Uk) F k
(x)
Then, the solution procedure of the MOTP problem
is summarized in the following steps.
Step 1: Consider the first objective function and
solve it as a single objective transportation problem
subject to the constraints (2) – (4). Continue this
process K times for K different objective functions.
If all the solutions (i.e. X 1
= X 2
= .... = X k
= ,
i = 1,2,...m, j = 1,2,..., n ) are the same, then one of
them is the optimal compromise solution [21] and
go to step 6. Otherwise, go to step 2
Step 2: Evaluate the kth objective function at the k
optimal solutions (k = 1, 2,...,K). In accordance to
the set of optimal solutions, determine its lower and
upper bounds (L k and
U k ) for each objective function.
Step 3: Define the membership function as
mentioned in Eq. (5)
Step 4: Construct the fuzzy programming problem
[29] P2 and find its equivalent LP problem P3
Step 5: Solve P3 by using an integer programming
technique to get an integer optimal solution and
evaluate the K objective functions at this optimal
compromise solution. Combining stage 1 and stage
2, we get an optimal solution.
Step 6: Stop to construct the membership function
of the MOTP problem (step 3) this solution
procedure requires the determination of upper and
lower bounds of each objective (step 2). After that,
Zadeh‟s min-operator [28] is used to develop a
linear compromise problem (P3) which is solved by
using any integer programming technique.
VII. NUMERICAL EXAMPLE
Consider the following multi – objective two stage
cost minimizing transportation problem. Here
supplies & demands are hexagonal fuzzy numbers.
a1 = (7, 9, 11, 13, 16, 20); a2 = (6, 8, 11, 14, 19, 25)
; a3 = (9, 11, 13, 15, 18, 20);
b1 = (6, 9, 12, 15, 20, 25); b2 = (6, 7, 9, 11, 13, 16);
b3 = (10, 12, 14, 16, 20, 24)
Using Robust ranking technique.
R(H) =
a1 = 25; a2 = 27; a3 = 28.5
b1 = 28.5; b2 = 20.5; b3 = 31.5
C1
=
C2
=
STAGE I:
We take a1=12, a2=13, a3=14.5
b1=14.5, b2=10, b3=15,
With respect to C1
, applying VAM, we get
x11 = 2; x12 = 10; x21 = 12.5; x23 = 0.5; x33 = 14.5
min z = 717.5 .
With respect to C2
, applying VAM we get

x11 = 2; x12 = 10; x23 = 13; x31 = 12.5; x33 = 2
min z = 885.5
F1
(X 1
) = 717.5; F1
(X 2
) = 930
F2
(X1
) = 865; F 2
(X 2
) = 885.5
i.e. 717.5 ≤ F1
≤ 930
865 ≤ F 2
≤ 885.5
The member ship function of both F1
(x) and F 2
(x)
are
μ1(F1
(x)) = =
μ2(F2
(x)) = =
Now Solve Max β
S. to
x11 + x12 + x13 = 12
x21 + x22 + x23 = 13
x31 + x32 + x33 = 14.5
x11 + x21 + x31 = 14.5
x12 + x22 + x32 = 10
x13 + x23 + x33 = 15
0.0282 x 11 + 0.0167x 12 + 0.0419x13 + 0.0175 x 21 +
0.0258 x 22 + 0.0285 x23 +0.0290x31 + 0.0110x32 +
0.0218 x33 + 0.2285β ≤ 1
0.0243 x 11+ 0.0246x 12+ 0.0339x13 + 0.0192 x 21+
0.0198x 22+ 0.0237x23 +0.0271x31+ 0.0370 x32+
0.0294 x33 +0.0232β ≤ 1
≥ 0 and integer, ∀ i, j
The optimal compromise solution X*
x11 = 2 ; x12 = 10 ; x21 = 12.5 ; x23 = 0.5 ; x33 = 14.5
;
The overall satisfaction β = 0.9956
The optimum values of the objective functions after
stage I are
F1
(X*) = 717.5
F2
(X*) = 860.5
Stage II:
We take a1=13, a2=14, a3=14
b1=14, b2=10.5, b3=16.5,
With respect to C1
, applying VAM, we get
x11 = 2.5; x12 = 10.5; x21 = 11.5; x23 = 2.5; x33 = 14
min z = 765.
With respect to C2
, applying VAM we get
x11 = 2.5; x12 = 10.5; x23 = 14; x31 = 11.5; x33
= 2.5
min z = 917
F1
(X 1
) = 765; F1
(X 2
) = 960.5
F2
(X1
) = 894; F 2
(X 2
) = 917
i.e. 765 ≤ F1
≤ 960.5
894 ≤ F 2
≤ 917
The member ship function of both F1
(x) and F 2
(x)
are
μ1(F1
(x)) = =
μ2(F2
(x)) = =
Now Solve Max β
S. to
x11 + x12 + x13 = 13
x21 + x22 + x23 = 14
x31 + x32 + x33 = 14
x11 + x21 + x31 = 14
x12 + x22 + x32 = 10.5
x13 + x23 + x33 = 16.5
0.0273 x 11 + 0.0161x 12 + 0.0406x13 + 0.0169 x 21 +
0.0250 x 22 + 0.0276 x23 +0.0281x31 + 0.0107x32 +
0.0211 x33 + 0.2035β ≤ 1
0.0234 x 11+ 0.0237x 12+ 0.0327x13 + 0.0185 x 21+
0.0191x 22+ 0.0229x23 +0.0262x31+ 0.0357 x32+
0.0284 x33 +0.0251β ≤ 1
≥ 0 and integer, ∀ i, j
The optimal compromise solution X*
x12 = 10.5 ; x13 = 2.5 ; x21 = 14; x33 = 14;
The overall satisfaction β = 0.8026
The optimum values of the objective functions after
stage II are
F1
(X*) = 771.25
F2
(X*) = 905.4
The optimal values of the objective functions
combining stage I and stage II are
F1
(X*) = 717.5+ 771.25 =1489
F2
(X*) = 860.5+ 905.4 =1766
Table:
Stage I Stage II Combine I & II
F1
(X*) 717.5 771.25 1489
F2
(X*) 860.5 905.4 1766

VIII. CONCLUSION
Transportation models have wide applications in
logistics and supply chain for reducing problems.
In this study , Fuzzy geometric programming
approach is used to determine the optimal
compromise solution of a multi-objective two stage
fuzzy transportation problem, in which supplies,
demands are Hexagonal fuzzy numbers and fuzzy
membership of the objective function is defined.
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Multi – Objective Two Stage Fuzzy Transportation Problem with Hexagonal Fuzzy Numbers Using Fuzzy Geometric Programming

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