Omron SYSMAC CS Series Instruction & Reference Manual page 602

3. Instructions
 Operand Specifications
Word addresses
Area
CIO WR HR
S
C OK OK OK
D
Flags
Name
Error Flag
Greater Than Flag
Less Than Flag
Carry Flag
Function
When the execution condition is ON, PIDAT(191) carries out target value filtered PID control with two
degrees of freedom according to the parameters designated by C (set value, PID constant, etc.). It
takes the specified input range of binary data from the contents of input word S and carries out the PID
action according to the parameters that are set. The result is then stored as the manipulated variable in
output word D.
The parameter settings are read when the execution condition turns from OFF to ON, and the Error
Flag will turn ON if the settings are outside of the permissible range.
If the settings are within the permissible range, PID processing will be executed using the initial values.
Bumpless operation is not performed at this time. It will be used for manipulated variables in
subsequent PID processing execution. (Bumpless operation is processing that gradually and
continuously changes the manipulated variable in order to avoid the adverse effects of sudden
changes.)
When the execution condition turns ON, the PV for the specified sampling period is entered and
processing is performed.
Autotuning
The status of the AT Command Bit (bit 15 of C+9) is checked every cycle. If this control bit is turned ON
in a given cycle, PIDAT(191) will begin autotuning the PID constants. (The changes in the SV will not
be reflected while autotuning is being performed.)
The limit-cycle method is used for autotuning. PIDAT(191) forcibly changes the manipulated variable
(max. manipulated variable ↔ min. manipulated variable) and monitors the characteristics of the
controlled system. The PID constants are calculated based on the characteristics that were observed,
and the new P, I, and D constants are stored automatically in C+1, C+2, and C+3. At this point, the AT
Command Bit (bit 15 of C+9) is turned OFF and PID control resumes with the new PID constants in
C+1, C+2, and C+3.
• If the AT Command Bit is ON when PIDAT(191) execution begins, autotuning will be performed first
and then PID control will start with the calculated PID constants.
568
AR T C DM EM
OK OK OK OK OK
Label
P_ER • ON if the C data is out of range.
• ON if the actual sampling period is more than twice the designated sampling period.
• ON if the manipulated variable output due to the limit cycle does not change for 9,999 seconds during
auto tuning.
• OFF in all other cases.
P_GT • ON if the manipulated variable after the PID action exceeds the upper limit.
• OFF in all other cases.
P_LT • ON if the manipulated variable after the PID action is below the lower limit.
• OFF in all other cases.
P_CY • ON while PID control is being executed.
• OFF in all other cases.
PID control
PV input (S)
Manipulated variable (D)
Indirect DM/EM
addresses
Con-
stants
@DM *DM
DR
@EM *EM
OK
OK OK --- ---
OK
Operation
Parameters (C to C+8)
CS/CJ/NSJ Series Instructions Reference Manual (W474)
Registers Flags
Pulse
bits
Indirect
IR TK CF
using IR
--- OK --- ---
TR
bits
--- ---