Siemens SIMATIC S5-95F - Page 260

Blocks and Their Functions S5-95F
Correction Rate Algorithm
The relevant correction increment dY
k
is computed at instant t= k
•
TA according to the following
formula:
• Without feedforward control (D11.5=1); XW is forwarded to the differentiator (D11.1=0)
dY
k
=K [(XW
k
- XW
k-1
) R+TI
•
XW
k
+ (TD (XW
k
- 2XW
k-1
+XW
k-2
)+dD
k-1
)]
=K (dPW
k
R+dI
k
+dD
k
)
• With feedforward control (D11.5=0); XW is forwarded to the differentiator (D11.1=0)
dY
k
=K [(XW
k
- XW
k-1
) R+TI
•
XW
k
+ (TD (XW
k
- 2XW
k-1
+XW
k-2
)+dD
k-1
)]+(Z
k
-Z
k-1
)
=K (dPW
k
R+dI
k
+dD
k
)+dZ
k
• Without feedforward control (D11.5=1); XZ is forwarded to the differentiator (D11.1=1)
dY
k
=K [(XW
k
- XW
k-1
) R+TI
•
XW
k
+ (TD (XZ
k
- 2XZ
k-1
+XZ
k-2
)+dD
k-1
)]
=K (dPW
k
R+dI
k
+dD
k
)
• With feedforward control (D11.5=0); XZ is forwarded to the differentiator (D11.1=1)
dY
k
=K [(XW
k
- XW
k-1
) R+TI
•
XW
k
+ (TD (XZ
k
- 2XZ
k-1
+XZ
k-2
)+dD
k-1
)]+(Z
k
-Z
k-1
)
=K (dPW
k
R+dI
k
+dD
k
)+dZ
k
P component I component D component k: k
th
sampleZ component
When XW
k
is applied: XW
k
=W
k
- X
k
PW
k
=XW
k
- XW
k-1
QW
k
=PW
k
- PW
k-1
=XW
k
-2XW
k-1
+XW
k-2
When XZ is applied: PZ
k
=XZ
k
- XZ
k-1
QZ
k
=PZ
k
- PZ
k-1
=XZ
k
-2XZ
k-1
+XZ
k-2
The result is: dPW
k
= (XW
k
- XW
k-1
)R
dI
k
=TI
•
XW
k
dD
k
= (TD
•
QW
k
+dD
k-1
) when XW is applied
= (TD
•
QZ
k
+dD
k-1
) when XZ is applied
dZ
k
=Z
k
- Z
k-1
Positioning Algorithm
The formula used to compute the correction rate algorithm is also used to compute the positioning
algorithm.
In contrast to the correction rate algorithm, however, the sum of all correction increments computed
(in DW 48), rather than the correction increment dY
k
is output at sampling instant t
k
.
9-6 EWA 4NEB 812 6210-02