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6
Fuzzy Controllers
This chapter describes various implementations and I/O characteristics of
fuzzy controllers.
Structure of a Fuzzy Controller
A fuzzy controller is composed of the following three calculation steps:
fuzzification, fuzzy inference, and defuzzification. Linguistic rules
integrated into the rule base of the controller implement the control strategy
that you base on engineering experience with respect to a closed-loop
control application.
A fuzzy controller has a static and deterministic structure, as shown in
Figure 6-1, which you can describe with an I/O characteristic curve.
e1
Rule Base
IF ... AND ... THEN ...
IF ... AND ... THEN ...
e2
u
IF ... AND ... THEN ...
en
IF ... AND ... THEN ...
Fuzzification
Fuzzy Inference
Defuzzification
Figure 6-1. Internal Structure of a Fuzzy Controller
In principle, there are two different implementation forms. With the first
type of implementation, the Offline Fuzzy Controller, you transform the
three-step calculation scheme into a reference table from which you can
derive the command values. You can use interpolation to calculate
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PID Control Toolset User Manual