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## Re: DAE daspk solver problem

 From: Sebastian Schöps Subject: Re: DAE daspk solver problem Date: Thu, 27 Oct 2016 00:29:52 -0700 (PDT)

```Lazy_Tom wrote
> f(1) = xdot(1)-x(2);
> f(2) = m*xdot(2)+x(5)*x(1);
> f(3) = xdot(3)-x(4);
> f(4) = m*xdot(4) + x(5)*x(3) +m*g;
> f(5) = x(1)^2 + x(3)^2 - 1;

I think there are a few typos, e.g., it should be -x(5)*x(3) in eq (4) but
this is probably not the issue here. You are trying to solve a very
difficult problem. This formulation of the pendulum is a DAE of index 3 and
afaik daspk can only deal with DAEs of index<3. There are many good books on
this topic. If you are looking for a good free ressource, you may want to
look at
https://www.mathematik.hu-berlin.de/~steffen/pub/introduction_to_daes_497.pdf
(page 2 and 13).

Seb.

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