Omron SYSMAC CJ - REFERENCE MANUAL 01-2008 Reference Manual page 816

Data Control Instructions
Control Item
data
Bits 00 to 11 AT Calculation Gain Set this parameter to adjust the
of C+9
C+10 Limit-cycle Hystere-
sis
Example 1:
Interrupting PID Control to
Perform Autotuning
Contents
contribution of the PID calcula-
tion results to the stored values.
Normally, leave this parameter
set to its default (0000).
• Increase the
emphasizing stability.
• Decrease the value when
emphasizing responsiveness.
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.
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 ( ) 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
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.
At the rising edge of W 000000 (OFF to ON), SETB(532) turns ON bit 15 of
D00209 (C+9) and starts autotuning. When autotuning is completed, the cal-
culated P, I, and D constants are written to C+1, C+2, and C+3. PID control is
then restarted with the new PID constants.
Setting range
0000 hex: 1.00 (Default)
0001 to 03E8 hex (1 to 1000);
(0.01 to 10.00, in units of 0.01)
value when
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.
MV output upper limit
Section 3-18
Change with
ON input
condition
Allowed
(These param-
eters are read
when autotun-
ing starts.)
Max. value of output range
777