Omron CS1G/H-CPUxxH Instructions Manual page 706

Data Control Instructions
Direction of Action
Reverse Action
Output
Adjusting PID Parameters
hunting, integral action to automatically correct any offset, and derivative
action to speed up the response to disturbances.
Step Response of PID Control Action Output
Step response
Deviation 0
Manipulated
variable
0
Ramp Response of PID Control Action Output
Ramp response
Deviation
0
Manipulated 0
variable
When using PID control, select either of the following two control directions. In
either direction, the MV increases as the difference between the SV and the
PV increases.
• Forward action: MV is increased when the PV is larger than the SV.
• Reverse action: MV is increased when the PV is smaller than the SV.
Output
Low SV High
temperature temperature
The general relationship between PID parameters and control status is shown
below.
• When it is not a problem if a certain amount of time is required for stabili-
zation (settlement time), but it is important not to cause overshooting,
then enlarge the proportional band.
Control by measured PID
SV
When P is enlarged
• When overshooting is not a problem but it is desirable to quickly stabilize
control, then narrow the proportional band. If the proportional band is nar-
rowed too much, however, then hunting may occur.
PID action
I action
P action
D action
PID action
I action
P action
D action
Forward Action
Low SV High
temperature temperature
Section 3-18
685