Bomag BW 219 DH-4 Service Training page 276

6.2
Service Training MESX
Control
Controlling describes the process during which an input value influences a distance (the
value to be controlled), following a fixed command. For this purpose all possible interfering
factors (e.g. temperature, humidity ...) must be known.
Input (w)
Closed loop control
Closed loop control is a process during which a value, the closed loop control value (e.g.
pressure), is continually measured and compared with a nominal value (guide value). The
result of this comparison will affect the closed loop control value, thereby adapting the closed
loop control value to the guide value.
This sequence occurs in a closed circuit, the co-called closed loop control circuit.
Input (w)
Marking
Operating path:
Measurement and
comparison of value to
be adjusted:
Reaction to faults
(generally):
Technical expense:
Performance in
unstable systems
Status: 21.12.2011
Author: T.Löw / TE
276
u
Control
+
e
Control
-
Closed loop control
closed
(closed loop control circuit)
Value to be adjusted is
measured and compared.
Counteracts to all faults
targeting the system to be
controlled.
Low expense:
Measurement of the value to
be controlled, comparison of
nominal and actual value,
power amplification
For unstable systems closed
loop controls must be used.
BOMAG
Disturbance variable (z)
Output (y)
Distance
Disturbance variable (z)
u
Output (y)
Distance
Control
open
(control chain)
Values to be controlled
are not measured and
compared.
Does not respond to
unknown faults
High expense if many
faults have to be
considered, low expense
if not faults occur.
In unstable systems
controls cannot be used.
Terminology
BEM, BOMAG Evib Meter
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