Siemens SIMATIC S5-90U System Manual page 253

S5-90U/S5-95U
W
R
- +
X TI
+
XW
0
TD
1
XZ
STEU
Bit 1
Figure 9-4. Block Diagram of the PID Controller
Table 9-2. Legend for the Block Diagram of the PID Controller (Figure 9.4)
Designation
K
R
TA
TN
TV
TI
TD
W
STEU
YH, dYH
Z
XW
X
XZ
Y, dY
OG/UG
BGOG
BGUG
YA, dYA
EWA 4NEB 812 6115-02b
Z
1 0
0
Z -Z
k k-1
+ dY
+
K
+
+ 1
0
STEU
Bit 0
YH, dYH
Explanation
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 error
Actual value
Substitute value for system error
Manipulated variable, manipulated increments
Upper limit/lower limit
Upper limit of the manipulated variable
Lower limit of the manipulated variable
Output value: YA Control Word Bit 3=1
dYA Control Word Bit 3=0
Integrated Blocks and Their Functions
BGOG
STEU
Bit 5
OG
Y
Sum-
ming
unit
+
Lim-
0
iter
+
1 dY
UG
Manual
function
STEU STEU
Bit 3 Bit 4
BGUG
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
STEU
Bit 2
0
YA,
dYA
1
0
9-9