Siemens SIMATIC S5-95F Manual page 258

Blocks and Their Functions
W
R
- +
X TI
XW
0
TD
1
XZ
STEU
Bit 1
Table 9-3. Legend for the Block Diagram of the PID Controller (Figure 9-2)
Designation
K
R
TA
TN
TV
TI
TD
W
STEU
YH, dYH
Z
XW
X
XZ
Y, dY
BGOG
BGUG
YA, dYA
9-4
1
0
Z -Z
k
+ dY
K
+
+ +
YH, dYH
Figure 9-2. Block Diagram of the PID Controller
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 of the manipulated variable
Lower limit of the manipulated variable
Output value :
Z
STEU
Bit 5
0
k-1
Sum-
ming
unit
+
0
1
1
0
Manual
function
STEU STEU
Bit 0 Bit 3
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
YA Control Word Bit 3=1
dYA Control Word Bit 3=0
BGOG
STEU
Bit 2
OG
Y
+
Lim-
iter
0
+
dY
1
UG
0
STEU
Bit 4
BGUG
EWA 4NEB 812 6210-02
S5-95F
YA,
dYA