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After first calling up the program part NYQUIST-DIAGRAM, the position of
the
critical point Pk=[+1;j0] or Pk=[-1;j0] must be entered. After this
selection
has been made, it is retained and shown in the graph until the program
part
has been reset.
Scale factor changes are always based on the scale of the first graph;
thus Re=+6 and Im=+j6 corresponds to scale factor 1.
If the scale selected is on interval M:=[2;12], then the unit circle
appears
additionally in the Nyquist-diagram. This way the viewer can compare the
RESULTS with the graph more easily.
If the locus has not been completely calculated after more than 10^8Hz or
1200 values (Re(Fo)), a corresponding warning will appear in the lower
window
of the screen.
If, for example, the quadrant for the actual start of the locus (given
through
Fo(w->o) of the result list) and the quadrant for the "Graph Start" just
shown
do not coincide, the scale factor or the coordinate`s zero point should
definitely be changed.
The exactness of the RESULTS is thereby increased and the processing time
is
considerably reduced. All RESULTS then stands in relation to the screen
window
shown.
If the parameter dead time Tt in the order of magnitude is given for the
other
control-loop time constants involved, the accompanying locus describes a
spiral or loop. The number of value-pairs then can easily exceed the
given
maximum. This is indicated by a corresponding statement.
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However, such a control is frequently unstable, making a correction of
the
parameter necessary all the same.
Thus, there is no disadvantage resulting from this for the user.
If the phase margin is between 0ø and 1ø, the text "Stab-Gr" (stability
boundary) is issued.
The exactness of the calculated RESULTS is around 0,01% and stands in
relation
to the respective frequency domain presented.
If all remaining parameters of a control are reset, the locus of the
remaining
control-loop member can be immediately shown.
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