Babylon university-uloom college for women- advanced intelligent applicationsknowledge base- zainab falah
Knowledge Base:
The KB establishes the fundamental part of the Mamdani FRBS. It
serves as the repository of the problem specific knowledge —that models
the relationship between input and output of the underlying system.
Notice that the KB contains two different information levels
1.
A Database (DB):
Containing :
 The linguistic term sets (the linguistic rules ).
 The membership functions.
 The scaling factors or scaling functions.
that are used to transform between the universe of discourse in
which the fuzzy sets are defined to the domain of the system input and
output variables.
The types of salling are:
a) Linear scalling:
Scaling allows it to define the fuzzy membership functions over a
normalised universe of discourse. This variable is normalised by applying
the parameterised scaling function, which incorporates the context
information through the parameters min and max(0 and 1), whether fixed,
tuned or learned scaling functions are employed.
b) Non-linear scaling:
This scalling provides a remedy to this problem as it modifies the relative
distribution and changes the shape of the membership functions.
2. Rule Base(RB):
A rule base (RB) is comprised by a collection of linguistic rules that
are joined by the also operator. In other words, multiple rules can fire
simultaneously for the same input.
The RB can present several structures.
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Babylon university-uloom college for women- advanced intelligent applicationsknowledge base- zainab falah
List Of Rules.
Decision Table :
It becomes an equivalent and more compact representation for the
same set of linguistic rules when only a few input variables (usually one
or two) are considered by the FRBS.
Example:
Consider an FRBS where two input variables, x1 and x2, and a single
output variable, y, are involved with the following term sets associated:
Parameter name
Type
Linguistic Labels
x1
x2
y
Input Var.
Input Var.
Output Var.
{small , medium , large }
{ short , medium , long }
{ bad , medium , good }
Q/ Give five rule for these variables expressed in rule base and decition
table:
Sol:
a)
Using rule base:
R1 : If ( x1 is small )
and ( x2 is short )
R2 : If ( x1 is small )
and ( x2 is medium ) Then (y is bad )
R3 : If ( x1 is medium ) and ( x2 is short )
Then (y is bad )
Then (y is medium )
R4 : If ( x1 is large )
and ( x2 is medium ) Then (y is medium )
R5 : If ( x1 is large )
and ( x2 is long )
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Then (y is good )
Babylon university-uloom college for women- advanced intelligent applicationsknowledge base- zainab falah
b)
Usinge decision table:
Small
medium
short
bad
medium
medium
bad
long
large
medium
good
Exercise:
Consider an FRBS where two input variables, x1 and x2, and a single
output variable, y, are involved with the following term sets associated:
Parameter name
Type
Linguistic Labels
x1
Input Var.
{zero , negative , positive }
x2
Input Var.
{ zero , positive , negative }
y
Output Var.
{ zero , positive , negative }
Give five rule for these variables expressed in rule base and decition table.
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