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PID control (Pr. 128 to Pr. 134)
(2) PID action overview
1) PI action
A combination of proportional control action (P) and integral control action (I) for providing a manipulated
variable in response to deviation and changes with time.
2) PD action
A combination of proportional control action (P) and differential control action (D) for providing a manipulated
variable in response to deviation speed to improve the transient characteristic.
3) PID action
The PI action and PD action are combined to utilize the advantages of both actions for control.
4) Reverse action
Increases the manipulated variable (output speed) if deviation X (set point - measured value) is positive, and
decreases the manipulated variable (output speed) if deviation is negative.
[Operation example for stepped changes of measured value]
[Operation example for proportional changes of measured value]
Deviation
Set point
Process value
Time
Time
Time
PI action
I action
P action
CAUTION
PI action is the sum of P and I actions.
Deviation
Set point
Process
value
Time
Time
Time
PD action
D action
P action
CAUTION
PD action is the sum of P and D actions.
Time
Time
Time
P action
D action
PID action
Set point
Process
value
Time
I action
y=at +bt+c
2
CAUTION
The PID action is the sum of P and I and D actions.
manipulated variable
manipulated variable
Set point
X > 0
X < 0
Process value
+
-
[Heating]
Deviation
Set point
Process value
Cold Increase the
Hot Decrease the