FX
3U
/FX
3UC
Series PLC User's Manual - Analog Control Edition
PID Instruction (FNC 88)
G-21
4 Auto Tuning
4.2 Step Response Method
A
Common Items
B
FX
3UC
-4AD
C
FX
3U
-4AD-ADP
D
FX
3U
-4DA-ADP
E
FX
3U
-4AD-PT
-ADP
F
FX
3U
-4AD-TC
-ADP
G
PID Instruction
(FNC 88)
4.2 Step Response Method
4.2.1 Parameters to be set by auto-tuning (step response method)
4.2.2 Auto tuning procedure
1 Transferring the output value for auto tuning to the output value
Set the output value for auto tuning to the maximum available output value multiplied by 0.5 to 1 for
the output equipment.
2 Setting the parameter , target value (SV), etc. that cannot be set in auto
tuning according to the system
Note that auto tuning may not be executed normally if the cautions described below are not fol-
lowed
1. Set items
2. Cautions on setting
1) Difference between the target value (SV) and the measured value (PV)
If the difference between the target value (SV) and the measured value (PV) is less than 150 when auto
tuning is started, auto tuning is not executed normally.
Accordingly, if the difference is less than 150, set the target value for auto tuning.
Set the target value again when auto tuning is completed.
2) Sampling time (T
S)
Make sure to set the sampling time for auto tuning to 1 second (1000 ms) or more.
It is recommended to set the sampling time considerably longer than the output change cycle.
3 Setting to ON bit 4 of +1 (operation setting) (ACT) to start auto tuning
When the variation from the measured value at the start of auto tuning to the target value reaches
1/3 or more, auto tuning is completed. And bit 4 of +1 (operation setting) (ACT) is
automatically set to OFF.
1. Important point
Start auto tuning while the system is stable.
If the system is unstable when auto tuning is started, auto tuning may not be executed normally.
Parameter Setting position Parameter Setting position
Operation setting (ACT)
+1, bit 0 (operation direction)
Integral time (T
I)
+4
Proportional gain (K
P)
+3
Differential time (TD)
+6
Set item and parameter Remarks
Target value (SV)
The difference from the measured value (PV) should be 150 or more.
(For the details, refer to "2. Cautions on setting" below.)
Sampling time (T
S) 1,000 ms or more (For the details, refer to "2. Cautions on setting" below.)
Input filter (α)
+2
Differential gain (K
D)
+5
When setting the input filter, set the differential gain to "0" usually.
Others Set other items, as necessary.
Set item Setting in PID instruction
Target value (SV)
Make sure that the difference from the measured value is 150 or
more when auto tuning is started.
S
3
S
3
S
3
S
3
S
3
S
3
S
3
D
S
3
S
1
S
3
S
3
S
3
S
1
S
3
S
3
S
3
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