Fuzzy Logic In The C200H-Fz001 - Omron SYSMAC C200H-FZ001 Operation Manual

Fuzzy Logic Theory
Defuzzification

1-3-2 Fuzzy Logic in the C200H-FZ001

Calculating Rule Grades
Condition Functions
6
After all of the rule grades are calculated, the grade for each label is calculated.
The grade for a label is called its fuzzy output. The fuzzy output is the maximum
rule grade for that label. The maximum value is taken because the rules are
linked by logical ORs. Taking the maximum value ensures that the results from
all of the rules are taken into account fairly. The final result is calculated from the
fuzzy outputs in an operation called defuzzification.
There are two methods of defuzzification available in the C200H-FZ001, the
center of gravity method and the maximum value method. The center of gravity
method determines the center of gravity using the fuzzy outputs as the weight
and the location of the label as the location. With this method, the location of the
center of gravity is the final result.
The maximum value method uses the location of the label with the maximum
fuzzy output as the final result. If two or more fuzzy outputs are equal to the maxi-
mum, either the leftmost (minimum) or rightmost (maximum) label location will
be selected. The programmer determines in advance whether the leftmost or
rightmost label location will be selected.
In this section, the fuzzy logic processing that was outlined in the previous sec-
tion is examined in detail. Fuzzy logic processing in the C200H-FZ001 is divided
into three steps: condition part processing, conclusion part processing, and de-
fuzzification.
Condition part processing involves calculating the rule grades. This is a two step
process because one rule can have up to 8 condition parts. First, the grade for
each condition part of a rule is calculated from its condition membership function
and the inputs, then the minimum grade is taken as the rule grade.
The rule in the following example has 3 condition parts.
Condition membership function
Grade
Input
Minimum grade = rule grade
The rule grades, which are used in conclusion part processing, are stored in
RAM and can be monitored with the FSS (Fuzzy Support Software).
A membership function can be defined for each label of each input. Since there
can be up to 7 labels for each of 8 inputs, a total of 56 condition membership
functions can be defined.
Another condition
membership function
Grade
Input
Another condition
membership function
Grade
Input
Section 1-3