set simulink time step

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Hongkai Dai
Hongkai Dai on 11 Jul 2011
Edited: John Kelly on 27 May 2014
I want to simulate a dynamics system 'mdl' using sim('mdl',parameters), and I want to get the simulation output at some specific time points, instead of time points determined by the ode solver. Is there any way that I can specify the time step of the simulink ode solver?
Like when using ode45, I can use ode45(odefun,tspan,y0) with tspan=0:0.1:1, can I still get simulation output at time points 0:0.1:1 with simulink?

Accepted Answer

Kaustubha Govind
Kaustubha Govind on 11 Jul 2011
Edited: John Kelly on 27 May 2014
For variable-step solvers, you can do this by setting the Output options parameter on the Import/Export Pane of the Configuration Parameters window to either 'Produce additional output' or 'Produce specified output only' and entering the time array in Output times.
  3 Comments
Hongkai Dai
Hongkai Dai on 11 Jul 2011
Thanks for your help! Do you know how to set the output options to "Produce specified output only" through command line?
Hongkai Dai
Hongkai Dai on 11 Jul 2011
Thanks, I have found out, I can specify option.OutputOption, and then pass sim('mdl',option)

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More Answers (2)

Fangjun Jiang
Fangjun Jiang on 11 Jul 2011
Yes, certainly you can! Why don't you try it and see the results.
Use the MATLAB supplied "f14" model as an example, you can specify a time vector with variable time step and then run simulation. open the model and make it to output the simulation time "tout" and "yout" at Simulation>Configuration Parameters...>Data Import/Export
t=[0:0.01:5,5.1:0.1:10]';
sim('f14',t);
all(t==tout)
ans =
1
>> size(tout)
ans =
551 1
>> size(yout)
ans =
551 2
  3 Comments
Kaustubha Govind
Kaustubha Govind on 11 Jul 2011
I don't think that is possible with fixed-step solvers. However, if what you want is to only get output signal values at specified time-steps, you can choose the least common divisor of your desired steps as the solver fixed-step and then extract the desired points from the logged outputs.
Fangjun Jiang
Fangjun Jiang on 11 Jul 2011
See my edited answer above. I added an example with time vector with variable time step.

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Fangjun Jiang
Fangjun Jiang on 11 Jul 2011
I guess a short answer to your question is YES. Since you already know how to use ode45(odefun,tspan,y0) with tspan=0:0.1:1, you can do the same with sim, sim('YouModelName',tspan) with tspan=0:0.1:1.
  1 Comment
Hongkai Dai
Hongkai Dai on 11 Jul 2011
Thanks a lot for your kind help! But Mathworks says such syntax are obsolete: http://www.mathworks.com/help/toolbox/simulink/ug/f11-61836.html#bsoh2ls. Anyway, your solution helps me a lot! Thanks!

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