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From: david s on 27 Oct 2009 12:30
"david s" <david.sabine760(a)gmail.com> wrote in message <hc4kcv$koe$1(a)fred.mathworks.com>...
> "Arnaud Miege" <arnaud.miege(a)nospam.mathworks.co.uk> wrote in message <hc4266$5j9$1(a)fred.mathworks.com>...
> >
> > >>
> > > Hi Arnaud,
> > > Thanks for your response . I tried to use the ode45 solver and the ode23s
> > > solver but i got the same error message . also i used relative tolerances
> > > =1e-3 and absoluate tolerances = auto . My model is a fuel cell model
> > > , it is composed of 6 inputs (the pressure of hydrogen ,the pressure of
> > > oxygen, the pressure of water, the humidity and the temperature) ,of 5
> > > state variables ,and of a 2 outputs (the voltage and the current ).
> > > If it is possible i can send you by email my simulink model that i did and
> > > the differential equations that describe this state space model .
> > > thanks in advance
> > >
> > > David
> > >
> >
> > Try usin
g ode15s or ode23t instead. Try setting the absolute tolerance to
> > something else other than auto, e.g. 1e-4. As the error message suggests,
> > try tightening the error tolerances to see if it improves (keep absolute at
> > least one order of magnitude smaller than relative). If it still doesn't
> > work, you might need to look at your model and see if there are elements
> > that could be modelled in a different manner or changed (for example, to get
> > rid of algebraic loops).
> >
> > You can also try to contac technical support:
> > http://www.mathworks.com/support/contact_us/index.html
> >
> > HTH,
> >
> > Arnaud
> >
> thanks again for you,
> i found that in the equation 5 of case (1) in my s_function m-file which is :
> dx5/dt=[(-1.2e10*u(1)*x(5))/( u(6)*log(abs(1.92e5*u(1)))+log(abs(1- 6432.3*u(1))))] - 1e6*u(1);
> when i cancel the last term of the equation which is ( 1e6*u(1) ) and try the simulink there were not any error message and i get a good output ,so i think that the problem is in this equation .
> where u1 is a pulse signal or a constant (u1 = 2.5e-6) and u6 = 353
> have you any idea about how can i play on this equation ?
> thanks

or i do not know if the error may be produced by the 2 logarithms in the same equation .
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