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Problem with DT State-Space Response #419
Description
Activity
The problem is that
H_ss_directis not actually a discrete time system, even though they way you created it makes it look like it should be. The actually calling signature forcontrol.StateSpaceisStateSpace(A, B, C, D[, dt])The final
dtargument is not a keyword argument but a positional argument. Hence the say to createH_ss_directisH_ss_direct = ctrl.StateSpace(A, B, C, D, True)In the call that you made,
H_ss_directhas timebaseNonewhich means that it can represent either a continuous time system or a discrete time system. The various time response functions all assume that if you don't specify a timebase then it is continuous. (If you want this type of "strict" checking inisdtime, you can usestrict=Truewhen you callisdtime.)At a minimum, there should be an error message printed with the call that you made, saying that
dtwas not recognized. Better (I think) would be to recognize thedtkeyword since it is a completely natural (and perhaps even better) way to create a discrete time system.It would be great if you want to submit a PR to fix this (remember to include docstrings and some unit tests that both capture the only case and test all new code that you add).
- linked a pull request that will close this issueRebased #431: Default dt is 0 #490
on Dec 31, 2020
Hi all,
First, congratulations for the wonderful work you've done by maintaining and creating the library!
I have found some issues working with DTLTI systems. More specifically, I am trying to simulate the step response of a DT system directly from its state-space representation. This realization is computed directly in the DT domain, without a sampling process. As you can see in the image below, there is a problem since the step response is blowing up. My intuition is that there is a bug since the DT system is being treated as if it were CT, but it is DT.
Exactly the same happens when the
dtparameter is set toNone. When I try to evaluate whether the SS representation is DT or CT, I get that it's being taken as both.I would appreciate any guidelines on how to fix this. I can do it myself and pull it :)
Kind regards,
Sergio Dorado-Rojas