LS Industrial Systems MASTER-K80S, Руководство пользователя

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Chapter 7 Usage of Various Functions
7-32
(c) Fig 2.10 shows examples of process control by forward and reverse actions, respectively.
Fig. 2-10 PV of forward / reverse action
f) Reference value
In general feedback control system shown as the Figure 2-10, the deviation value is obtained by the difference of
PV and SV. P, I, and D operations are performed based on this deviation value. However, each of P, I, and D
operations use different deviation values according to the characteristics of each control actions. The expression
of PID control is as following;
⎥⎦
⎤
⎢⎣
⎡
+ + =
∫ t
dt
dEd
Td ds s Ei
Ti
Ep K MV
0
) (
1
MV : Manipulate value
K: Proportional gain
Ti: Integral time
Td : Derivative time
Ep: Deviation value for proportional action
Ei : Deviation value for integral action
Ed: Deviation value for derivative action
The deviation values of P, I, and D action is described as following equations;
PV Ed
PV SV Ei
PV SV b Ep
− =
− =
− × =
The b of the first equation is called as reference value. It can be varied according to the load disturbance of
measurement noise.
Fig. 2-11 Diagram of simple feedback system
Process
-1
+
SV PV MV
PID