Reproduce the StateSpaceModel example given in the documentation?

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1

I tried to reproduce an example from the documentation running M12 on Windows10 but failed to get same result:

eqns = {L i'[t] == Subscript[v, l][t], 
   Subscript[v, c]'[t] == 1/C i[t], R i[t] == Subscript[v, r][t],
   Subscript[v, l][t] + Subscript[v, c][t] + Subscript[v, r][t] == 
    Subscript[v, s][t]};
m2 = StateSpaceModel[
  eqns, {i[t], Subscript[v, l][t], Subscript[v, c][t], 
   Subscript[v, r][t]}, {Subscript[v, s][t]}, {i[t]}, t]

The result that I get looks like

01-12-_2019_17-44-54.jpg
01-12-_2019_17-44-54.jpg207×107 4.8 KB

Each of the grey squares represents a complicated expression which can be view im Mathematica while hovering over it. The representation of the state space model looks complete different compared to the one given in the documentation:

01-12-_2019_17-48-55.jpg
01-12-_2019_17-48-55.jpg694×176 24.8 KB

Any ideas?

2

Michael,

I agree it no longer works the same in V12. I reported the bug to Support.

If you do not do the Descriptor system and use one of the options for StateSpaceRealization, it works:

StateSpaceModel[eqns, {i[t], Subscript[v, l][t], Subscript[v, c][t], 
  Subscript[v, r][t]}, {Subscript[v, s][t]}, {i[t]}, t, 
 StateSpaceRealization -> "ControllableCompanion"]

Also, to view all of the StateSpaceModel terms, you can click on the “S” in the upper right corner and it will expand the gray squares.

Regards,

Neil

3

Thank you for your reply, I was not aware of the trick with clicking the the “S”.

Best regards, Michael

4

Michael,

I forgot to mention that if you click it again, it will compress back to the gray squares. This also works on TransferFunctionModels. This feature is missing from the documentation – I’ll report the omission. We found it by accident.

Regards,

Neil