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Chapter 2. SPECIFICATIONS
2 - 10
4) PID Action
(1) PID action controls the control object with the manipulation quantity produced by (P+I+D) action.
(2) PID action when a given deviation has occurred is shown as the following Fig. 2.8.
[Fig. 2.8] PID action at a constant deviation
5) PID Processing Expression
PID expressions are of measured value derivative type.
Expressions Parameters names
E
n
=
==
= SV −
−−
− PV
n
MV
n
=
==
= MV
n-1
+ K
p
✕
✕✕
✕
(E
n
−
−−
−E
n-1
)
+ K
p
✕
✕✕
✕
S/K
I
✕
✕✕
✕
E
n
+ K
p
✕
✕✕
✕
K
d
/S
✕
✕✕
✕
(2PV
n
−
−−
−PV
n-1
−
−−
−PV
n-2
)
MVn
MVn-1
En
En-1
Kp
Ki
Kd
S
PVn
PVn-1
PVn-2
: Present Manipulated Value
: One-step-previous
Manipulated Value
: Present deviation
: Previous deviation
: Proportional constant
: Integral constant
: Derivative constant
: Control cycle (100 ms)
: Process value
: One-step-previous
Process Value
: Two-step-previous
Process value