GE C30 Instruction Manual page 230

5.6 CONTROL ELEMENTS
A general form of a PID regulator in the s domain is shown below.
y
r
w
The following terms apply to the block diagram:
• y is the process signal
• r is the setpoint signal
• w is the tracking signal
5
• u is the regulator output
• K is the proportional gain
• b is the setpoint weighting
• Td is the derivative time constant
• N is the derivative limit
• Ti is the integral time constant
• Tt is the anti-windup time constant
In discrete form, the equations for the regulator are:
Where T is the sampling time and AW is a flag which enables anti-windup. The incremental form of the above equation is:
S
Where:
5-102
b
-1
-
e
+
K
Ti
Figure 5–40: PID BLOCK DIAGRAM
e k ( ) r k ( ) y k ( )
= –
p k ( ) K br k ( ) y k ( ) ( )
= –
T
 
d
d k ( ) ----------------------- - × d k 1 (
= –
 
T NT
+
d S
u k ( ) p k ( ) i k ( ) d k ( )
= + +
e k ( )
KT
S
( ) i k ( ) ---------------------- -
i k 1
+ = +
T
i
Du k ( ) u k ( ) u k 1
=
Dp k ( )
=
C30 Controller System
+
K
+
sKTd
1+sTd/N
+
1
s
+
1
Tt
+ -
kT N
 
d
) ----------------------- - × ( y k ( ) y k 1 (
– –
 
T NT
+
d S
T
 
S
------ × ( w k ( ) u k ( ) ) ×
AW
+ –
 
T
t
( )
– –
Di k ( ) Dd k ( )
+ +
5 SETTINGS
p
+
d +
u
+
i
) )
–
(EQ 5.1)
(EQ 5.2)
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