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I am new to Matlab and I need to perform a simple task. I have an input function u(t)=2t-1 and an output function

y(t)=(-4/45)e^3t+ (1/5)e^(-2t)-1/3t-1/9

I have to find the corresponding behavior model, defined via a transfer function and then simulate the behavior model in Matlab/Simulink. I am not sure what approach I should use. What I have done so far is that I transferred the input and output function in the s-domain and then I calculated the transfer function. What does it mean to simulate the behavior model in Matlab? Can anyone please help me? I am a very beginner. Thank you very much!

user3331949
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1 Answers1

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If you've already done the Laplace transform and calculated the transfer function in s-domain, I think it means applying the transfer function to an arbitrary transient input and calculating the response.

The transfer function is based on the response due to a unit step function.

If you have an input that is something other than a unit step function (e.g. a sinusoid), you'd calculate the response as follows:

  1. Transform the arbitrary input function to s-space.
  2. Multiply it by the transfer function to the response in s-space.
  3. Transform the response in s-space back to the time domain.

This is how Laplace transforms work.

duffymo
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  • What is an arbitrary transient input? I have to build a model in Simulink. I have seen tutorials which use as input the Step block. but I don't know exactly what it is. Thank you – user3331949 Jun 02 '15 at 18:16
  • Thank you very much. This is very helpful. I have transformed the input function in s-space. How to implement it in Simulink using the source blocks? – user3331949 Jun 02 '15 at 18:33
  • The input function in s-space domain is U(s)=2/(s^2) - 1/s – user3331949 Jun 02 '15 at 18:35
  • If that's your input function in s-space, then you need to multiply that by the transfer function to get the output response in s-space, then transform that back to the time domain. – duffymo Jun 02 '15 at 18:45