Rockwell Automation RSLogix 5000 Fuzzy Designer - Manual (Page 14)

Publication LOGIX-UM004A-EN-P - March 2007
14 Get Started with FuzzyDesigner
Crisp and Fuzzy
For temperature readings, you can classify a reading into three sets,
Low, Medium and High. Each set contains values in a given interval,
and the intervals do not overlap. This means that a single reading or
value is uniquely classified into one set.
However, vague classifications are more realistic as there is usually no
sharp border between Low, Medium, or High temperatures. In this
situation, however, a single numerical value might fall into multiple
categories. For example, it might be partially Medium, and partially
High as shown in the following figure. A specification of how much
the particular value of temperature fits into the meaning of the label of
the category (fuzzy set) is described by the membership function,
which becomes a design parameter of the fuzzy controller.
TIP
Degree of membership (DOM) is a value describing how well
the particular value of the variable (in this case, temperature)
fits the meaning of the label of the set, Medium. If the DOM is
1, the current temperature is understood as 100% Medium.
Low Medium High
range
20 150
range
20
range
20 150
temperature temperature temperature
1
0
degree of membership
(level of classification)
1
0
degree of membership
(level of classification)
Crisp Value Crisp Value
1.00 Medium Medium
0.0 High High
0.0 Low Low
1.00 Medium Medium
0.0 High High
0.0 Low Low
Classification
Result