Omron CJ Series Operation Manual page 82

Setting the PID Constants
Timing Chart
Start AT Bit
PID Constants
Calculated Flag
(System-controlled.)
Change PID
Constants Bit
(User-controlled.)
PID Constants in the
input words of DM
Area (CJ1W-TC@@@
to CPU Unit transfer.)
PID Constants in output
words of DM Area (CPU
Unit to CJ1W-TC@@@
transfer)
Effects of Changes to the
PID Constants
The PID Constants Calculated Flag will be turned OFF automatically when
you turn ON the Change PID Constants Bit.
Refer to Appendix B Sample Programs for an example ladder program that
performs the steps outlined above.
1
0
AT in progress
Set to 1 by the system
1
after calculations are
completed.
0
1
0
The PID constants in the
output area of DM are the
same.
PID constants (user
Output area data read to the
CJ1W-TC@@@ Unit's RAM by
I/O refreshing.
The following tables show the effects on the PV when each PID constant is
changed (increased or decreased.)
• Changing P (The Proportional Band)
Increasing P
SP
Decreasing P
SP
• Changing I (The Integral Time)
Increasing I
SP
Decreasing I
SP
The PID constants haven't
been refreshed from the
Automatic
CPU Unit if this bit is ON.
calculations
completed.
When this bit goes
ON, the PID Con-
stants Calculated
Flag is unlatched
and goes OFF.
Contains the PID
The PID constants in the output
constants calculated by
area of DM are the same (the
autotuning.
calculated PID constants.)
Use the PID Constants Calculated Flag as an
input condition to trigger the transfer of the
calculated PID constants from the input words
in DM Area to the output words in DM Area.
PID constants automatically calculated by autotuning
Output area data read to the
Nothing is read to the
CJ1W-TC@@@ Unit's RAM by
Unit's RAM during this
I/O refreshing.
interval.
Section 3-9
It will take longer to reach the
set point (SP), but the process
value (PV) will not overshoot.
The PV will overshoot and there
will be hunting, but the PV will
reach the SP quickly.
Increases the time required to
reach the SP, but reduces hunt-
ing, overshooting, and under-
shooting.
Overshooting and undershoot-
ing will occur.
Hunting will occur.
The PV will rise quickly.
59