Integral Action (I Action) - Mitsubishi Electric MELSEC iQ-R Series User Manual

Integral action (I action)

An integral action that continuously changes the manipulated value (MV) to eliminate the deviation (E) when there is any. The
offset caused by a proportional action can be eliminated.
In an integral action, the time taken for the manipulated value (MV) of the integral action after the generation of the deviation
(E) to become the manipulated value (MV) of a proportional action is called integral time and expressed as T
shows the difference of the actions depending on the integral time T
Condition
When the integral time T
I
When the integral time T
I
The following figure shows an integral action of step responses of when the deviation (E) is a fixed value.
Deviation
(E)
Manipulated
value (MV)
An integral action is used as a PI action in combination with a proportional action, or a PID action in combination with a
proportional action and a derivative action. An integral action cannot be used by itself.
APPX
338
Appendix 4 PID
is short
is long
E
Time
K ·E
P
T
I
Time
.
I
Integral action
The integral effect becomes large and the time to eliminate the offset
becomes short. However, the temperature process value (PV) tends to
fluctuate around the set value.
The integral effect becomes small and the time to eliminate the offset
becomes long.
Manipulated value of the Proportional action + Integral action
Manipulated value of the Integral action
Manipulated value of the Proportional action
. The following
I