Thread Subject:

Derivative input at time xxx is Inf or Nan

Hi,

I get the following error while i try to run my simulation.
I have also tried using a memory block in the feedback line as suggested in few threads but it did not change the result. Pls do drop in your suggestions.

??? Derivative input 1 of 'LinearModel/Plant/Electrical/Integrator1' at time 0.002875 is Inf or
NaN. Stopping simulation. There may be a singularity in the solution. If not, try reducing the
step size (either by reducing the fixed step size or by tightening the error tolerances).

Thank you,
Venkat

On 4 Jan, 18:46, "venkata ragavan " <meetraga...@gmail.com> wrote:
> Hi,
>
> I get the following error while i try to run my simulation.
> I have also tried using a memory block in the feedback line as suggested in few threads but it did not change the result. Pls do drop in your suggestions.

What do you not understand? The message? Or what to do with it?

If you don't know what a 'singularity' is, it is a bad numerical
condition which essentially means that the computations break
down. One example is divisions by 0, but there are many others.

The way to handle this problem is to find out where and why
it occurs, and if possible, restate the simulation to handle
this singularity.

This means that you need to investigate the simulation in
minute detail and find out where the problems occur. And
yes, *you* have to do that, since you are the only person
to have access to your models.

Rune

"venkata ragavan " <meetragavan@gmail.com> wrote in message <gjqskq$57r$1@fred.mathworks.com>...
> Hi,
>
> I get the following error while i try to run my simulation.
> I have also tried using a memory block in the feedback line as suggested in few threads but it did not change the result. Pls do drop in your suggestions.
>
> ??? Derivative input 1 of 'LinearModel/Plant/Electrical/Integrator1' at time 0.002875 is Inf or
> NaN. Stopping simulation. There may be a singularity in the solution. If not, try reducing the
> step size (either by reducing the fixed step size or by tightening the error tolerances).
>
> Thank you,
> Venkat

  I have no way of knowing the details of your simulation. I do know that if your derivative is approximated by finite differences and if your step size happens to be exactly zero, you will get a zero divided by zero situation which produces a NaN:

 f'(x) = (approx) (f(x+a)-f(x))/a = 0/0 --> NaN

when a equals zero.

Roger Stafford

"venkata ragavan " <meetragavan@gmail.com> wrote in message <gjqskq$57r$1@fred.mathworks.com>...
> Hi,
>
> I get the following error while i try to run my simulation.
> I have also tried using a memory block in the feedback line as suggested in few threads but it did not change the result. Pls do drop in your suggestions.
>
> ??? Derivative input 1 of 'LinearModel/Plant/Electrical/Integrator1' at time 0.002875 is Inf or
> NaN. Stopping simulation. There may be a singularity in the solution. If not, try reducing the
> step size (either by reducing the fixed step size or by tightening the error tolerances).
>
> Thank you,
> Venkat

I've had the same error and didn't realise that the output was just to big so the Inf error was thrown. For example set the simulation time to 0.0028 and see if the output isn't to big.

-alex

> > ??? Derivative input 1 of 'LinearModel/Plant/Electrical/Integrator1' at time 0.002875 is Inf or
> > NaN. Stopping simulation. There may be a singularity in the solution. If not, try reducing the
> > step size (either by reducing the fixed step size or by tightening the error tolerances).
> >
> > Thank you,
> > Venkat
  

I'm also getting the same error at some point in my simulation. Have realized it is due to the times when my input is zero, yet it is inevitable because my input is actually solar irradiance, and must be zero during some points. What should i do about it?
Thank you ,
Hilda

"Hilda Hilda" wrote in message <ircmoo$a1m$1@newscl01ah.mathworks.com>...
>
> > > ??? Derivative input 1 of 'LinearModel/Plant/Electrical/Integrator1' at time 0.002875 is Inf or
> > > NaN. Stopping simulation. There may be a singularity in the solution. If not, try reducing the
> > > step size (either by reducing the fixed step size or by tightening the error tolerances).
> > >
> > > Thank you,
> > > Venkat
>
>
> I'm also getting the same error at some point in my simulation. Have realized it is due to the times when my input is zero, yet it is inevitable because my input is actually solar irradiance, and must be zero during some points. What should i do about it?
> Thank you ,
> Hilda

Hi,
You can try different solvers in configuration parameters.

HTH,
saif