Siemens SIMATIC S5-100U System Manual page 250

Integrated Blocks and Their Functions
W
R
- +
X TI
+
XW
0
TD
1
XZ
STEU
Bit 1
Figure 9-7. Block Diagram of the PID Controller
Table 9-6. Legend for the Block Diagram of the PID Controller
Designation
K
R
TA
TN
TV
TI
TD
W
STEU
YH, dYH
Z
XW
X
XZ
Y, dY
BGOG
BGUG
YA, dYA
9-16
Z
1 0
0
Z -Z
k k-1
+ dY
+
K
+
+ 1
0
STEU
Bit 0
YH, dYH
Proportional coefficient:
R parameter (usually 1000)
Scan time
Integral-action time
Derivative-action time
Constant TI
Constant TD
Setpoint
Control word
Output value:
Disturbance variable
System deviation
Actual value
Substitute value for system deviation
Manipulated variable, manipulated increments
Upper limit of the manipulated variable
Lower limit of the manipulated variable
Output word : YA Control Word Bit 3=1
dYA Control Word Bit 3=0
BGOG
STEU
Bit 5
OG
Y
Sum-
ming
unit
+
0
Limiter
+
1 dY
UG
Manual
function
STEU STEU
Bit 3 Bit 4
BGUG
Explanation
K>0 direct acting
K<0 reverse acting
TI=Scan time TA/Integral action time TN
TD=Derivative action time TV/Scan time TA
YH Control Word Bit 3=0
dYH Control Word Bit 3=1
S5-100U
STEU
Bit 2
0
YA,
dYA
1
0
EWA 4NEB 812 6120-02b