Setting up Compax3 C3I22T11
260 192-120114 N5 C3I22T11 June 2008
Open/Closed Loop frequency response measurement
In order to be able to analyze the transmission behavior of subordinate systems
(such as for example speed control, current control or mechanical system), the
influence of the superposed controls on the measurement must be avoided.
Influence of a superposed system on the frequency response measured
In the simplest case, the superposed controls are switched off completely (Open
Loop) This provides the best measurement results due to the elimination of any
influence caused by the superposed controls.
This is, however, rarely possible for reasons of safety or feasibility.
Caution!
Many systems are not stable without control!
Position as well as speed control are switched off du-
ring measurement ==>
no measurement on z-axes!
If you want to analyze for example the mechanic system of a z-axis, the position
control as well as the speed control must remain active.
In systems subject to friction it may be necessary in order to improve the quality of
the measurement, to
move the system with a superimposed speed (see page
263), which is howeveronly possible with
a closed loop measurement.
Influence of an active superposed control on the result of the measurement
At the left without, at the right with the influence of the superposed control
In order to attenuate the influence of the superposed controls, the controller band-
width is reduced to such an extent, that their influence on the measurement is neg-
ligible.
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