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From: Davide Sanseverinati on 13 Jul 2010 13:34
Hi everybody

i'm trying to identify the coefficients of a transfer function with the GUI identification toolbox, starting from this model:
>model_ele_Q
>Continuous-time IDPOLY model: y(t) = [B(s)/F(s)]u(t) + e(t)
>B(s) = -120.2 s^3 - 1395 s^2 - 371.7 s + 0.3259
>
>F(s) = s^4 + 25.12 s^3 + 802.1 s^2 + 217.9 s + 49.65

I've inserted my experimental data in the proper field. In the field 'estimate' i select 'by initial model' and specified 'model_ele_Q'. Then, when press 'estimate' i receive this error message 'Index exceeds matrix dimensions' without further explanations. Some knows what could be the cause?

Davide
From: Davide Sanseverinati on 14 Jul 2010 09:36
"Davide Sanseverinati" <john.doe.nospam(a)mathworks.com> wrote in message <i1i82d$39a$1(a)fred.mathworks.com>...
> Hi everybody
>
> i'm trying to identify the coefficients of a transfer function with the GUI identification toolbox, starting from this model:
> >model_ele_Q
> >Continuous-time IDPOLY model: y(t) = [B(s)/F(s)]u(t) + e(t)
> >B(s) = -120.2 s^3 - 1395 s^2 - 371.7 s + 0.3259
> >
> >F(s) = s^4 + 25.12 s^3 + 802.1 s^2 + 217.9 s + 49.65
>
> I've inserted my experimental data in the proper field. In the field 'estimate' i select 'by initial model' and specified 'model_ele_Q'. Then, when press 'estimate' i receive this error message 'Index exceeds matrix dimensions' without further explanations. Some knows what could be the cause?
>
> Davide


I've discovered that the error message occur only when i use merged experimental data and use 'model_ele_Q' as initial model at same time. If i use a single experimental data sequence with 'model_ele_Q', or the merged data and a generic ARX the error doesn't occur.

Hope that someone knows how to help me

thanks
From: Davide Sanseverinati on 14 Jul 2010 11:51
"Davide Sanseverinati" <john.doe.nospam(a)mathworks.com> wrote in message <i1keg4$86t$1(a)fred.mathworks.com>...
> "Davide Sanseverinati" <john.doe.nospam(a)mathworks.com> wrote in message <i1i82d$39a$1(a)fred.mathworks.com>...
> > Hi everybody
> >
> > i'm trying to identify the coefficients of a transfer function with the GUI identification toolbox, starting from this model:
> > >model_ele_Q
> > >Continuous-time IDPOLY model: y(t) = [B(s)/F(s)]u(t) + e(t)
> > >B(s) = -120.2 s^3 - 1395 s^2 - 371.7 s + 0.3259
> > >
> > >F(s) = s^4 + 25.12 s^3 + 802.1 s^2 + 217.9 s + 49.65
> >
> > I've inserted my experimental data in the proper field. In the field 'estimate' i select 'by initial model' and specified 'model_ele_Q'. Then, when press 'estimate' i receive this error message 'Index exceeds matrix dimensions' without further explanations. Some knows what could be the cause?
> >
> > Davide
>
>
> I've discovered that the error message occur only when i use merged experimental data and use 'model_ele_Q' as initial model at same time. If i use a single experimental data sequence with 'model_ele_Q', or the merged data and a generic ARX the error doesn't occur.
>
> Hope that someone knows how to help me
>
> thanks


Another thing: choosing in the 'estimate'->'linear parametric model'->'initial state'->'ZERO' instead of 'Auto' , the error doesn't occur, but results of the estimation are very bad
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