Re: matrix exponential used by the control package

On Mon, Jul 20, 2020 at 4:38 PM Torsten Lilge1960 Blue Heron Drive, <
[email protected]> wrote:

> Hi everyone,
>
> the control package uses the SLICOT function mb05nd [1]
> (__sl_mb05nd__()) instead of the octave function expm() for the matrix
> exponential. The problem with mb05nd is that when discretizing a static
> gain in state space results in
>
> >> [a,b,c,d] = ssdata (c2d (ss (tf (1,1)),1))
> a = [](1x0)
> b = 0
> c = [](1x0)
> d = 1
>
> Instead, using expm() leads to the correct result
>
> >> [a,b,c,d] = ssdata (c2d (ss (tf (1,1)),1))
> a = [](0x0)
> b = [](0x1)
> c =
> [](1x0)
> d = 1
>
> Are there any reasons against using expm()?
>
> Torsten
>
>
> [1] http://slicot.org/objects/software/shared/doc/MB05ND.html
>
>
> Is there a difference in speed?
If it is slower then we should look and see where the '0" is coming from.

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