GE C30 Instruction Manual page 227

5 SETTINGS
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
• 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:
e k  
p k  
d k  
u k  

i k
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:
GE Multilin
+

b
+
-1
e
+
K

Ti
+
Tt
+

Figure 5–40: PID BLOCK DIAGRAM
r k   y k  
= –
K br k   y k    
= –
T
  
d
----------------------- -   
d k 1
= – –
  
T NT
+
d S
p k   i k   d k  
= + +
e k   T
KT

S
S
 i k   
------
1 ---------------------- -
+ = + +

T
T
t
i
Du k   u k   u k 1 
= –
Dp k  
= +
C30 Controller System
p
K
d +
sKTd
1+sTd/N
i
1
s
1
-
kT N

d
----------------------- -   y k   y k 1   
– –

T NT
+
d S

 w k   u k    
AW
–


–
Di k   Dd k  
+
5.6 CONTROL ELEMENTS
+

u
+
(EQ 5.1)
(EQ 5.2)
5-103
5