Ny-Series Instructions Reference Manual (W560 - Omron NY532-5400 Reference Manual

Set point
Autotuning hysteresis
Manipulated variable
MV upper limit
MV lower limit
The manipulated variable is
set to the MV upper limit.
When the deviation reaches 0, the
manipulated variable is set to the MV
lower limit.
When the deviation becomes greater than
the autotuning hysteresis, the manipulated
variable is set to the MV upper limit again.
Autotuning is executed during PID control (i.e., when the value of Run is TRUE) if the value of StartAT
changes to TRUE. If StartAT is TRUE when Run changes to TRUE, autotuning is executed at the start
of PID control. When autotuning is completed normally, the calculated PID constants are used immedi-
ately. Autotuning is canceled if the value of StartAT changes to FALSE during autotuning (i.e., when
ATBusy is TRUE). If autotuning is canceled, PID control is started again with the previous PID con-
stants.
Execution Timing of PID Control
PID control is repeated periodically. PID processing is performed when the PIDAT instruction is exe-
cuted in the user program. However, if sampling period SampTime has not elapsed since the last time
PID processing was performed, PID processing is nor performed. If the elapsed time since the last time
PID processing was executed exceeds SampTime, the excess time (elapsed time − SampTime) is car-
ried forward to the next period. This is shown in the following diagram.
Task period = 60 ms and SampTime < 60 ms
The task period is greater than or equal to SampTime, so PID processing is executed once every task period.
Task period
PIDAT
60 ms
PID processing
executed.
Time

NY-series Instructions Reference Manual (W560)

Autotuning executed.
Process value
Task period Task period
PIDAT
PIDAT
60 ms
PID processing PID processing
executed. executed.
2 Instruction Descriptions
Time
Time
Task period
PIDAT
60 ms 60 ms
PID processing PID processing
executed.
Task period
AutoPID
executed.
2-677
2