nonlinear model in simulink and designing pid controller

Hi guys

when I design for a nonlinear model in simulink a pid controller, and I want to run the simulink, it gives me bellow image.

(max step size is 0.2s , please go to configuration parameter and set "automatic solver parametric selection" to "none". although, I do that again it gives me this warning and when I see the scop, it does not give me a good result, it gives me just 0 in output instead of giving 2 things( output and input).

I attach also my slx file.

[Enrico Anderlini]

The file you have attached has no PID controller.

Anyway, it looks to me that the problem is that you are using an automatic solver, which selects a very large time step. You can disable the warning, but the problem is there. If the time discretisation is too rough, you can select a solver manually. Say ode4 (4th-ordeer Runge-Kutta) with a predefined time step.

[azam ghamari]

hello

I have a pid controller. please see the file. and also I did it( with fixed time 0.001) and it gives me this figure. while when I use the variable step, it gives me totally different result!

please see the attached files.

[nor zulaiman]

can i get your simulink pic

Answer 1

[Rhea Chandy]

It is my understanding that you are having some difficulty in choosing a solver for your model.

The automatic solver recommends a fixed or variable step solver based on your maximum step size. If you’re not satisfied with the results from the auto solver, I suggest manually choosing the solver and comparing the different results with the tradeoffs. For example, decreasing the step size in a fixed-step solver will increase the accuracy of the results but increases the time required to simulate the system.

This guide can help you in choosing various solver for the dynamics of your model.