Soft Computing and Its Applications, Volume One

Fuzzy Implications and Fuzzy If-Then Models 495

modeling of a plant for control. Just as with the modern control theory, we can design

a fuzzy controller based on a fuzzy model of a plant if a fuzzy model can be identied.

Fuzzy modeling in the latter sense is not necessarily viewed as qualitative modeling

unless the derivation of a qualitative model from the identied fuzzy model is dis-

cussed. It is, of course, quite interesting to derive qualitative control rules based on the

qualitative model of a plant.

For example, assume that we have a dynamical plant model such as:

• If is positive and is positive, then is positive big,

• If is negative ...