LG K7F-PIDA User Manual

Page 17

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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

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