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Options for slow-fast decomposition


opt = freqsepOptions returns the default options for freqsep.


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


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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 contains 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, relax the accuracy constraint by increasing the "SepTol" factor (see "freqsepOptions" for details).

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

options = freqsepOptions('SepTol',5e10);
[Gs,Gf] = freqsep(G,2,options);

Now freqsep successfully separates the dynamics.

slowpole = pole(Gs)
slowpole = -1.9999
fastpole = pole(Gf)
fastpole = 2×1 complex

  -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 quotes. You can specify several name and value pair arguments in any order as Name1,Value1,...,NameN,ValueN.

Example: 'SepTol',5

Accuracy loss factor 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 G1+G2, differ by no more than SepTol times the absolute accuracy of the computed value of G(s). Increasing SepTol helps separate modes straddling the slow/fast boundary at the expense of accuracy.

Output Arguments

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

See Also

Introduced in R2014a