Technical data

Index k k times sampling
Switch Setting Effect
S1
CONTROL
BIT 1
0
1
The system error XW
k
is supplied to
the derivative unit.
The derivative unit can be supplied
with another signal via XZ.
S2
CONTROL
BIT 0
0
1
Manual operation
Automatic
S3
CONTROL
BIT 3
0
1
Position algorithm
Velocity algorithm
S4
CONTROL
BIT 5
0
1
With feedforward control
Without feedforward control
STEU control word You obtain a function corresponding to the switch settings of the
block diagram by assigning parameters to the PID controller, i.e. by
setting the control bits in the control word STEU. The continuous
controller is intended for fast control systems, e.g. in process
engineering for pressure, temperature or flow rate control.
PID algorithm The controller itself is based on a PID algorithm. Its output signal can
either be output as a manipulated variable (position algorithm) or as a
change of manipulated variable (velocity algorithm).
You can disable the individual P, I and D actions by setting their
parameters R, TI and TD to zero. This allows you to implement any
controller structure you require, e.g. PI, PID or PD controllers.
Differentiator You can supply the derivative unit either with the system error XW or
a disturbance or the inverted actual value -x can be supplied via the
XZ input.
Disturbance compensation If you require a precontrol of the actuator without dynamic behaviour
to compensate for the influence of a disturbance, then a disturbance Z
measured in the process can be fed forward to the control algorithm.
In manual operation, this is replaced by the preselected manipulated
variable YM.
6
OB 250/251: Closed-Loop Control/ PID Algorithm
CPU 928B Programming Guide
C79000-B8576-C898-01
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