How can I get the instantaneous step size value in variable step solver at a simulink model?

Hello everyone,

This is an urgent stuation. I got a proble to get the value of instantaneous step size value in variable step solver. In my simscape model there is also a runge kutta solver function that I wrote and I need a h value which is a h=step_value/10. I dont want to use fixed step solver. That is why I need to know step value for each time step. I would be appreciated if you help me.

Answer 1

[Uday Pradhan]

Hi, you can use the "Clock" block in Simulink to get the current simulation time and the "memory" block to store this value for each step. In each step, subtract the output of "Memory" block (i.e. previous time step) from the current output of "Clock" to get the current step size. Here is a sketch of the workflow:

I hope this helps!

[Taha Oguz Özen]

Thank you for your suggestion.

Actually, I need to know the step size for the time I'm in (Present time step). Is there any way to write the present time step size. However, I will try your suggestion.

[Walter Roberson]

What step size do you expect at time 0 ?

[Taha Oguz Özen]

Now I am using fixed variable and my stepsize value is 0.001. (fixed_step_size=0.001)

My model calculates next step's X value with Runge Kutta 4 and runge needs its own step size (h).

In my current model I calculated h= fixed_step_size/10.

After RK4 is calculated X, I use X as a input of the next step. This is the loop like that.

I want to do this with variable step size but I couldn't find a way to get Present time step.

[Walter Roberson]

https://blogs.mathworks.com/simulink/2012/01/22/advanced-s-function-techniques-scheduling-future-events/ might give some useful hints perhaps?

https://www.mathworks.com/help/simulink/sfg/s-function-concepts.html