An introduction to fuzzy math
Fuzzy math differs from conventional math primarily in the area of set
theory. For example in a conventional AND statement both statements must
be true for the statement to be true. However, in fuzzy logic statements are
not always true or false, they merely have varying levels of confidence.
The table below exibits the differences in how an AND statement is applied in
conventional and fuzzy systems. As can clearly be seen the AND statement in
a fuzzy system is merely the minimum confidence value of the two values.
| conventional |
|
|
fuzzy |
|
|
| A |
B |
A AND B |
Fuzzy A |
Fuzzy B |
A AND B |
1 1 0 0
|
1 0 1 0
|
1 0 0 0
|
.700 .345 .000 .985
|
1.000 .625 .453 .245
|
.700 .345 .000 .245
|
The OR statement is also different in a fuzzy system as opposed to a conventional
system. Once again the table below demonstrates how an OR statement functions
in both a conventional and fuzzy system. The table demonstrates that the OR
statement returns the maximum value of its two operatives. Thus, the OR is essentially
the opposite of the AND statement, under a fuzzy system.
| conventional |
|
|
fuzzy |
|
|
| A |
B |
A AND B |
Fuzzy A |
Fuzzy B |
A AND B |
1 1 0 0
|
1 0 1 0
|
1 1 1 0
|
.700 .345 .000 .985
|
1.000 .625 .453 .245
|
1.000 .625 .453 .985
|
The concept of the fuzzy set is also key to many applications of fuzzy logic.
A set in conventional mathematics is very simple. A set is merely a collection of
numbers or things. However, in fuzzy math the definition of a set is slightly
different. A fuzzy set is a list of values, which describes to what degree
an object belongs to a variety of characteristics. The fuzzy set listed below
is an example of how a variety of temperatures might be classified.
| temp. in Farenheit |
very cold |
cold |
cool |
moderate |
warm |
hot |
brain baking |
20 30 40 50 60 70 80 90 100 110
|
.850 .275 .100 .000 .000 .000 .000 .000 .000 .000
|
.150 .450 .400 .300 .000 .000 .000 .000 .000 .000
|
.000 .275 .400 .500 .000 .000 .000 .000 .000 .000
|
.000 .000 .100 .300 .300 .100 .000 .000 .000 .000
|
.000 .000 .000 .000 .500 .800 .400 .100 .000 .000
|
.000 .000 .000 .000 .200 .100 .500 .700 .400 .100
|
.000 .000 .000 .000 .000 .000 .100 .200 .600 .900
|
|