Mitsubishi Electric 800 Series Instruction Manual (Function page 423

[Example of action when the measured value changes proportionately]
Set point
Measured value
P action
D action
PD
action
(Note) PD action is the result of P and D actions being added together.
 PID action
PID action is a combination of PI and PD action, which enables control that incorporates the respective strengths of these
actions.
Set point
Measured value
P action
I action
D action
PID action
(Note) PID action is the result of all P, I and D actions being added together.
 Reverse action
When deviation X = (set point - measured value) is a plus value, the manipulated amount (output frequency) is increased, and
when the deviation is a minus value, the manipulated amount is decreased.
 Forward action
When deviation X = (set point - measured value) is a minus value, the manipulated amount (output frequency) is increased,
and when the deviation is a plus value, the manipulated amount is decreased.
Relationship between deviation and manipulated amount (output frequency)
PID action setting
Reverse action
Forward action
422
16. (A) Application Parameters
16.4 PID control
Deviation
Time
Time
Time
Deviation
Time
Time
Time
2
y = at + bt + c
Time
[Heating]
+ X>0
Cold
Set
X<0 Hot
point
-
Feedback signal
(measured value)
[Cooling]
X>0
+
Too cold
Set
Hot
X<0
point
-
Feedback signal
(measured value)
Deviation
Plus Minus
Deviation
Increase
Decrease
Measured value
Measured value
Decrease
Increase
Deviation
Set point
Set point