Output of transfer function given impulse response and input the

In summary, the conversation discusses finding the Laplace transform of x(t) and h(t), multiplying the Laplaced values to get Y(s), and then finding the inverse Laplace to get y(t). It also mentions that the circled term in the book is not present and that the e5t term goes away in the Laplace transform due to the convolution integral. The conversation also mentions that there are two other alternatives to the one-sided Laplace transform: the Fourier transform and the two-sided Laplace transform. The latter is rarely used, but the Fourier transform gives the same answer. Finally, it is concluded that convolution is a better method than the Fourier route.
  • #1
jaus tail
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Homework Statement


upload_2018-2-9_10-5-47.png


Homework Equations


Find laplace of x(t) and h(t)
Multiply the laplaced values to get Y(s)
Find inverse laplace to get y(t)

The Attempt at a Solution


upload_2018-2-9_10-17-34.png

In book the circled term isn't there. Why does that go away?
Book gets y(t) as
upload_2018-2-9_10-8-58.png

In laplace why does the e5t term go away?
 

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  • #2
You will fin that the answer derives from the convolution integral. That method is valid for all time -∞ < t < ∞. The Laplace transform you're familiar with is most likely the one-sided Laplace transform which assumes x(t) = 0 for t < 0, so not applicable here.

There are two other alternatives: the Fourier transform and the two-sided Laplace transform. The latter is seldom encountered (see footnote) while the Fourier is appropriate and gives the same answer.

[Footnote: Then Brooklyn Poly's Professor John G. Truxal's venerable "Automatic Feedback Control System Synthesis" invokes it in preference to the Fourier].
 
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Likes jaus tail
  • #3
Thanks. Convolution is better than the Fourier route.
 

1. What is a transfer function?

A transfer function is a mathematical representation of the relationship between the input and output of a system. It describes how the system responds to different inputs and can be used to analyze and design control systems.

2. How is the output of a transfer function determined?

The output of a transfer function is determined by multiplying the input by the transfer function itself. This can be done in the time domain using convolution or in the frequency domain using multiplication.

3. Can the output of a transfer function be calculated from the impulse response and input?

Yes, the output of a transfer function can be calculated from the impulse response and input using convolution. The impulse response is convolved with the input to produce the output.

4. How does the input affect the output of a transfer function?

The input directly affects the output of a transfer function. A different input will result in a different output, as the transfer function describes the relationship between the two.

5. Are there any limitations to using a transfer function to analyze systems?

Yes, there are limitations to using a transfer function. It assumes the system is linear, time-invariant, and has no delays. It also does not take into account any external disturbances or noise in the system.

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