S1 = 7/8: Override Control - Siemens SIPART DR22 Manual

Manual

1.5.4.9 S1 = 7/8: Override control

wi
w
ES
SES
tS
w
SL
w
Δw
w
EΔ
FE8
x1I
FE1
xI=x1I+c1⋅x2I+c3
x2I
FE2
xII
FE3
Sb
Figure 1-41 Principle representation S1 = 7/8
In the override control (limiting control, disconnecting control) two controllers are connected
parallel, the main controller (Controller I) and the limiting controller (Controller II) which act on a
common actuator. The manipulated variables of both controllers are mutually limited by the in
this case controlled parameters YA (S1=7) or YE (S1=8). This gives a controlled variable
limiting related to the setpoint set or active in both controllers.
One of the two controllers -- preferably the main controller -- is always intervening and controls
the process. The non-intervening controller then has a control difference which controls it to the
limited manipulated variable. In this case all further integration is prevented so that no integral
saturation takes place. Disconnection always takes place at the latest when the control diffrence
in the non-intervening controller reverses. Changes in the controlled variable in the direction of
the control difference reversal also lead to disconnection via the P-part (possibly also D-part).
This gives a particularly good dynamic behavior.
By the arrangement of two controllers, better adaptation to the different time behaviors of the
two controlled systems is achieved than with a Minimum- or Maximum selection of the control
differences. The possible implementation by Minimum or Maximum selection of the manipulated
variables can lead to dynamic problems due to integral saturation of the non-intervening
controller.
SIPART DR22 6DR2210
C79000-G7476-C154-03
0000 0000
wI
tS
I
INT∧CB
I
SL
wII
0000 0000
1.5 Functional description of the structure switches
1.5.4 Controller types (S1, S49 to S53)
xI
wI
Main controller
wI
+
PID-controller I
--
xI
Min
selec-
tion
Max
xII
--
+
PID-controller II
wII
Limiting controller
wII
xII
1 Technical Description
000
y
H
yaI
YA YE
YE YA
yaII
y
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