776
Data Control Instructions Section 3-18
Note 1. When the unit is designated as 1, the range is from 1 to 8,191 times the
period. When the unit is designated as 9, the range is from 0.1 to 819.1 s.
When 9 is designated, set the integral and derivative times to within a
range of 1 to 8,191 times the sampling period.
2. Setting the 2-PID parameter (
α) to 000 yields 0.65, the normal value.
When the manipulated variable output limit control is enabled (i.e., set to
“1”), set the values as follows:
0000 ≤ MV output lower limit ≤ MV output upper limit ≤ Max. value of output range
Example 1:
Interrupting PID Control to
Perform Autotuning
At the rising edge of CIO 000000 (OFF to ON), the work area in D00211 to
D00240 is initialized according to the parameters (shown below) set in
D00200 to D00208. After the work area has been initialized, PID control is
executed and the manipulated variable is output to CIO 0020.
While CIO 000000 is ON, PID control is executed at the sampling period
intervals according to the parameters set in D00200 to D00210. The manipu-
lated variable is output to CIO 0020.
The PID constants used in PID calculations will not be changed even if the
proportional band (P), integral constant (Tik), or derivative constant is
changed after CIO 000000 turns ON.
Bit 15 of C+9 AT Command Bit This control bit starts autotuning.
• Set the AT Command Bit to 1
to perform autotuning. (Auto-
tuning can be started while
PIDAT(191) is being exe-
cuted.)
• This bit is turned OFF auto-
matically when autotuning is
completed.
Autotuning will be interrupted if
the AT Command Bit is turned
OFF manually. In this case, the
PID constants will be enabled if
they were already calculated
when autotuning was inter-
rupted.
As a Control Bit:
•0
→ 1:
Executes autotuning.
•1
→ 0:
Interrupts autotuning.
(PID(191) turns the bit OFF
automatically when autotun-
ing is completed.
As a Flag:
0: Autotuning is not being exe-
cuted.
1: Autotuning is being executed.
Allowed
Bits 00 to 11
of C+9
AT Calculation Gain Set this parameter to adjust the
contribution of the PID calcula-
tion results to the stored values.
Normally, leave this parameter
set to its default (0000).
• Increase the value when
emphasizing stability.
• Decrease the value when
emphasizing responsiveness.
0000 hex: 1.00 (Default)
0001 to 03E8 hex (1 to 1000);
(0.01 to 10.00, in units of 0.01)
Allowed
(These param-
eters are read
when autotun-
ing starts.)
C+10 Limit-cycle Hystere-
sis
Sets the hysteresis when the
limit cycle is generated. The
default setting for reverse opera-
tion turns ON the MV with a hys-
teresis of SV−20%.
Increase this setting if a proper
limit cycle cannot be generated
because the PV is unstable.
However, the AT accuracy will
decline if the Limit-cycle Hyster-
esis is higher than necessary.
0000 hex: 0.20% (Default)
0001 to 03E8 hex:
0.01 to 10.00% in units of 0.01%
FFFF hex: 0.00%
Note The percentage is with
respect to the input range.
Control
data
Item Contents Setting range Change with
ON input
condition
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