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6.4 Design of a simple fuzzy PID-controller
The most commonly used controller is a PIDcontroller. This example describes the design of a very
simple fuzzy PID-controller with only 3 rules. The
input values of the FPID-controller are the error
between the reference r and the controlled value y, the
sum of the error and the change of error. The pure
fuzzy module (FID-module) then has a PID-behaviour.
The same dynamic behaviour could be attained by
using the error, the change of error and the 2nd change
of error as input values and an integration element used
after the defuzzified output.
All input and output values can be changed by using
scaling factors (scaling values from -16 to 16 are
possible). For this purpose a scaling macro or a scaling
subroutine can be used.
The following structure (fig. 32) represents one
possibility for a FPID-controller.
FID-module
ke
ek(T)
kse
kde
µ(e)
ruleµ(se)
base
µ(u)
uk (T)
ku
µ(de)
Fig. 31: Fuzzy controller with PID behaviour.
FID - User´s guide
(c) 1993-97 FDG-Systems N. Exler
Page: 108