MATLAB: Discrete time simulations sampling rate question

Question

Hello,

I was hoping to get some help regarding inputting discrete time signals into Simulink. I've attached the structure used to input the signal and the simple model I used to see if the signal is being input properly.

I've left the .time structure variable empty as recommended in documentation Load Data to Test a Discrete Algorithm.

The signal it self was sampled every 5 seconds.

What I don't really understand is how to properly configure the solver for discrete simulations. Following Recommended Settings for Discrete Simulattions I set the step size as Auto and it doesn't work. When I choose a step size of 0.05 the signal is displayed but what I want to know is why if I choose 5 seconds as step size which is the sample time of the signal why that doesn't work also and the step size has to be so small.

Any help much appreciated.

Thanks!

Answer 1

Hi

The output for step size of 5 seconds and 0.005 seconds are the same. The only difference is that there should be enough simulation time to accomodate the whole simulation data given. For 0.005 seconds of step size, 60-80 seconds of stop time is sufficient, but for a step size of 5 seconds, a stop time of 5*20000 (20000 samples of data given) seconds is necessary for the entire signal to be shown up in the scope block. So, try changing the stop time to 100000 seconds in case of 5 second stepsize.

Hope it helps!