Omron Sysmac CJ Series, Operation Manual

Page: 82 / 117

59
Setting the PID Constants Section 3-9
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.
Timing Chart
Effects of Changes to the
PID Constants The following tables show the effects on the PV when each PID constant is
changed (increased or decreased.)
• Changing P (The Proportional Band)
• Changing I (The Integral Time)
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)
PID constants (user
Output area data read to the
CJ1W-TC
@@@ Unit’s RAM by
I/O refreshing.
Nothing is read to the
Unit’s RAM during this
interval.
Output area data read to the
CJ1W-TC
@@@ Unit’s RAM by
I/O refreshing.
PID constants automatically calculated by autotuning
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.
Contains the PID
constants calculated by
autotuning.
The PID constants in the output
area of DM are the same (the
calculated PID constants.)
The PID constants in the
output area of DM are the
same.
Set to 1 by the system
after calculations are
completed.
AT in progress
The PID constants haven’t
been refreshed from the
CPU Unit if this bit is ON.
Automatic
calculations
completed.
When this bit goes
ON, the PID Con-
stants Calculated
Flag is unlatched
and goes OFF.
1
0
1
0
1
0
Increasing P It will take longer to reach the
set point (SP), but the process
value (PV) will not overshoot.
Decreasing P The PV will overshoot and there
will be hunting, but the PV will
reach the SP quickly.
Increasing I Increases the time required to
reach the SP, but reduces hunt-
ing, overshooting, and under-
shooting.
Decreasing I Overshooting and undershoot-
ing will occur.
Hunting will occur.
The PV will rise quickly.
SP
SP
SP
SP