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freqsepOptions

Options for slow-fast decomposition

Syntax

  • opt = freqsepOptions
  • opt = freqsepOptions(Name,Value) example

Description

opt = freqsepOptions returns the default options for freqsep.

example

opt = freqsepOptions(Name,Value) returns an options set with the options specified by one or more Name,Value pair arguments.

Examples

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Separate Nearby Modes by Adjusting Tolerance

Decompose a model into slow and fast components between poles that are closely spaced.

The following system includes a real pole and a complex pair of poles that are all close to s = -2.

G = zpk(-.5,[-1.9999 -2+1e-4i -2-1e-4i],10);

Try to decompose the model about 2 rad/s, so that the slow component cotains the real pole and the fast component contains the complex pair.

[Gs,Gf] = freqsep(G,2);
Warning: One or more fast modes could not be separated from the slow modes. To
force separation, increase the absolute or relative tolerances ("AbsTol" and
"RelTol" options). Type "help freqsepOptions" for more information. 

These poles are too close together for freqsep to separate. Increase the relative tolerance to allow the separation.

options = freqsepOptions('RelTol',1e-4);
[Gs,Gf] = freqsep(G,2,options);

Now freqsep successfully separates the dynamics about 2 rad/s.

slowpole = pole(Gs)
fastpole = pole(Gf)
slowpole =

   -1.9999


fastpole =

  -2.0000 + 0.0001i
  -2.0000 - 0.0001i

Input Arguments

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Name-Value Pair Arguments

Specify optional comma-separated pairs of Name,Value arguments. Name is the argument name and Value is the corresponding value. Name must appear inside single quotes (' '). You can specify several name and value pair arguments in any order as Name1,Value1,...,NameN,ValueN.

Example: 'AbsTol',1e-4

'AbsTol' — Absolute tolerance for decomposition0 (default) | nonnegative scalar

Absolute tolerance for slow-fast decomposition, specified as a nonnegative scalar value. freqresp ensures that the frequency responses of the original system, G, and the sum of the decomposed systems Gs+Gf, differ by no more than AbsTol + RelTol*abs(G). Increase AbsTol to help separate nearby modes, at the expense of the accuracy of the decomposition.

'RelTol' — Relative tolerance for decomposition1e-8 (default) | nonnegative scalar

Relative tolerance for slow-fast decomposition, specified as a nonnegative scalar value. freqresp ensures that the frequency responses of the original system, G, and the sum of the decomposed systems Gs+Gf, differ by no more than AbsTol + RelTol*abs(G). Increase RelTol to help separate nearby modes, at the expense of the accuracy of the decomposition.

Output Arguments

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opt — Options for freqsepfreqsepOptions options set

Options for freqsep, returned as a freqsepOptions options set. Use opt as the last argument to freqsep when computing slow-fast decomposition.

See Also

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