IMO Precision Controls K7 Series User Manual page 98

Chapter 7 Usage of Various Functions
E = -PV
E = SV-PV
PV
(2) Realization of PID control on the PLC
In this chapter, it will described that how to get the digitized formula of the P, I, and D terms. Then, the pseudo code of
PID control will be shown.
a) P control
The digitized formula of P control is as following;
( )
P n
K : proportional gain constant
b : reference value
SV : set value
PV : present value
The continuous formula of I control is as following;
K : proportional gain constant
Ti : integral time
e(s) : deviation value
By deviation about t, we can obtain;
K × Td
K
k / Ti
Fig. 2-13 The block diagram of anti-windup control system
Fig. 2-14 The PV output characteristics with different Tt values.
[
= × ( ) − ( )
K b SV n PV n
b)I control
K
t
∫
) ( = ( )
t I e s ds
I(t) : integral term
0
Ti
Actuator model
MV
+
–
+
1 / Tt
Tt = 3
Tt = 2
Tt = 1
]
n : sampling number
7-
U
Actuator
+
+
Es
SV
Time