Derivative Action (D Action); Pid Action - Mitsubishi Electric MELSEC iQ-R Series User Manual

Derivative action (D action)

A derivative action adds the manipulated value (MV) proportional to the variation rate to eliminate the deviation (E) when it
occurs. A derivative action can prevent the control target from changing significantly due to disturbance.
In a derivative action, the time taken for the manipulated value (MV) of the derivative action after the generation of the
deviation (E) to become the value obtained by multiplying
called derivative time and expressed as T
Condition
When the derivative time T is short
D
When the derivative time T is long
D
The following figure shows a derivative action of step responses of when the deviation (E) is a fixed value.
Deviation
(E)
(1)
Manipulated (2)
value (MV)
T
D
(1) Manipulated value (MV) in a derivative action
(2) Manipulated value (MV) in a proportional action
A derivative action is used as a PD action in combination with a proportional action, or PID action in combination with a
proportional action and an integral action. A derivative action cannot be used by itself.

PID action

A PID action executes the control using the manipulated value (MV) calculated by adding the proportional action, integral
action, and derivative action. The following figure shows a PID action of step responses of when the deviation (E) is a fixed
value.
Deviation
(E)
Manipulated
value (MV)
.
D
E
Time
1
-
1
K E × × e
P
K E
P
Time
Time
PID action
I action
PI action
P action
D action
Time
1
1 -
×e
by the manipulated value (MV) of a proportional action is
Derivative action
The derivative effect becomes small.
The derivative effect becomes large. However, the temperature process value
(PV) tends to fluctuate around the set value in short cycles.
A
APPX
339
Appendix 4 PID