Defuzzification is the process of converting the degrees of membership of output linguistic variables within their linguistic terms into crisp numerical values. Consider the following rules:
| (1) | IF Vehicle Position x is Center (degree of membership = 0.8) |
AND (Minimum) | Vehicle Orientation β is Left Up (degree of membership = 1.0) = 0.8 |
| THEN Steering Angle φ is Negative Small | |||
| (2) | IF Vehicle Position x is Right Center (degree of membership = 0.1) |
AND (Minimum) | Vehicle Orientation β is Left Up (degree of membership = 1.0) = 0.1 |
| THEN Steering Angle φ is Negative Medium | |||
These two rules specify two non-zero values for the Steering Angle φ output linguistic variable:
| Negative Medium Negative Small |
to a degree of to a degree of |
�0.1 �0.8 |
|
Note�� Fuzzy controllers use an implication method to scale the membership functions of output linguistic variables before performing defuzzification. |
A fuzzy controller can use one of several mathematical methods to perform defuzzification: Center of Area (CoA), modified Center of Area (mCoA), Center of Sums (CoS), Center of Maximum (CoM), or Mean of Maximum (MoM). Selecting a defuzzification method depends on the context of the design you want to calculate with the fuzzy controller.