Rockwell Automation RSLogix 5000 Fuzzy Designer - Manual (Page 33)

Publication LOGIX-UM004A-EN-P - March 2007
FuzzyDesigner Component Library 33
User Defined Filter
You set the numerator and denominator coefficients b
0
, b
1
, …b
m
and
a
1
, …a
n
directly (the parameters are entered in the specified order
separated by the space character).
Butterworth Low Pass Filter
This filter can be created by specifying a normalized cutoff frequency
q, taken from the interval [0.01, 1], and the order of the filter (1,2,3).
Bode Plot of the Butterworth Low-Pass Filter
This normalized frequency q corresponds to the absolute frequency
ω
c
= q
ω
n
, where
ω
n
= π / T
s
is the Nyquist frequency for the sampling
period T
s
.
Connections
The output link of the input port is connectable to all components
expecting a crisp value at the input. This includes the following
components:
• Input Linguistic Variable
• Output Port
• Output Takagi-Sugeno Variable (accepts crisp values only)
• PID (accepts crisp values only)
WARNING
All dynamical terms in a fuzzy system (filters, PID controllers)
have to share the common sampling period Ts; otherwise the
system will not work correctly.
ω
c
|H(jω )|
0dB
ω