Thread Subject:

simulink stepsize problem

Hi,

I'm trying to do optimization (using Genetic Algorithm) using a simulink model as the objecive function. I used ode23 slover. For some parameter values in the simulink model, I got repeated warnings as following:

Warning: Unable to reduce the step size without violating minimum step size of 6.664677009193448e-14 for 1 consecutive times at time 18.75939805946777. Continuing simulation with the step size restricted to 0.664677009193448e-14 and using an effective relative error tolerance of 0.001038911124337621, which is greater than the specified relative error tolerance of 0.001. This usually may be caused by the high stiffness of the system. Please check the model 'modular_sim_tester' or increase the Max consecutive min step size violation parameter in the solver configuration panel.
> In call_modular_sim at 333
  In genetic at 194

I also tried ode15s, there was no warning this time, but the code just went to the end in a few minutes without any output.

Any sugguestions are appreciated.
Thanks a bunch

Jia

"Jia Zhao" <sixteenboys@yahoo.com.cn> wrote in message <gbm8s9$92a$1@fred.mathworks.com>...
> Hi,
>
> I'm trying to do optimization (using Genetic Algorithm) using a simulink model as the objecive function. I used ode23 slover. For some parameter values in the simulink model, I got repeated warnings as following:
>
> Warning: Unable to reduce the step size without violating minimum step size of 6.664677009193448e-14 for 1 consecutive times at time 18.75939805946777. Continuing simulation with the step size restricted to 0.664677009193448e-14 and using an effective relative error tolerance of 0.001038911124337621, which is greater than the specified relative error tolerance of 0.001. This usually may be caused by the high stiffness of the system. Please check the model 'modular_sim_tester' or increase the Max consecutive min step size violation parameter in the solver configuration panel.
> > In call_modular_sim at 333
> In genetic at 194
>
> I also tried ode15s, there was no warning this time, but the code just went to the end in a few minutes without any output.
>
> Any sugguestions are appreciated.
> Thanks a bunch
>
> Jia

Hi,

I think that this warning message come from your Simulink model! but not from the GA process... Maybe the current values found by the genetic algorithm cause some trouble during the simulations of the process.

Cheers,

V. Morio
PhD student in Automatic Control
IMS lab./University of Bordeaux, France

"Jia Zhao" <sixteenboys@yahoo.com.cn> wrote in message <gbm8s9$92a$1@fred.mathworks.com>...
> Hi,
>
> I'm trying to do optimization (using Genetic Algorithm) using a simulink model as the objecive function. I used ode23 slover. For some parameter values in the simulink model, I got repeated warnings as following:
>
> Warning: Unable to reduce the step size without violating minimum step size of 6.664677009193448e-14 for 1 consecutive times at time 18.75939805946777. Continuing simulation with the step size restricted to 0.664677009193448e-14 and using an effective relative error tolerance of 0.001038911124337621, which is greater than the specified relative error tolerance of 0.001. This usually may be caused by the high stiffness of the system. Please check the model 'modular_sim_tester' or increase the Max consecutive min step size violation parameter in the solver configuration panel.
> > In call_modular_sim at 333
> In genetic at 194
>
> I also tried ode15s, there was no warning this time, but the code just went to the end in a few minutes without any output.
>
> Any sugguestions are appreciated.
> Thanks a bunch
>
> Jia

Hi Jia, I have the same problem as u had, please answer if you solved tha problem.
Thanks so much.

Leyla

hi
I am also having the same trouble as u and it has put on halt.....do u know a way out...in case yes...just let me know..

would be a grt help..


thnx...




"Jia Zhao" <sixteenboys@yahoo.com.cn> wrote in message <gbm8s9$92a$1@fred.mathworks.com>...
> Hi,
>
> I'm trying to do optimization (using Genetic Algorithm) using a simulink model as the objecive function. I used ode23 slover. For some parameter values in the simulink model, I got repeated warnings as following:
>
> Warning: Unable to reduce the step size without violating minimum step size of 6.664677009193448e-14 for 1 consecutive times at time 18.75939805946777. Continuing simulation with the step size restricted to 0.664677009193448e-14 and using an effective relative error tolerance of 0.001038911124337621, which is greater than the specified relative error tolerance of 0.001. This usually may be caused by the high stiffness of the system. Please check the model 'modular_sim_tester' or increase the Max consecutive min step size violation parameter in the solver configuration panel.
> > In call_modular_sim at 333
> In genetic at 194
>
> I also tried ode15s, there was no warning this time, but the code just went to the end in a few minutes without any output.
>
> Any sugguestions are appreciated.
> Thanks a bunch
>
> Jia