Obtaining Step Response for Linear Systems in Sinusoidal Frequency Domain

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Discussion Overview

The discussion revolves around obtaining the step response of a linear system when the transfer function is provided in the sinusoidal frequency domain as a complex function of angular frequency ω. The scope includes theoretical relationships between transfer functions, impulse responses, and step responses.

Discussion Character

  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • One participant asks how to obtain the step response from a transfer function given in the sinusoidal frequency domain.
  • Another participant suggests that understanding the relationship between the transfer function and the impulse response, as well as the relationship between the impulse response and the step response, is essential.
  • A different participant questions the typical method for obtaining the step response from the transfer function and mentions the equivalence of the functions when substituting s with jω.
  • A participant references a 1959 publication that provides a direct method for determining transient response from frequency response, expressing gratitude for the community's input.
  • Another participant requests a summary of the findings from the referenced publication.
  • One participant states that to find the impulse response, only the real part of the transfer function is needed and provides a formula for calculating the impulse response using integration over the real part of the transfer function.

Areas of Agreement / Disagreement

Participants do not reach a consensus on a single method for obtaining the step response, and multiple approaches and references are discussed without resolving which is the most effective.

Contextual Notes

The discussion includes references to specific mathematical relationships and integrals that may depend on assumptions about the transfer function and its properties, which are not fully explored or resolved in the thread.

Boudy
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The transfer function of a linear system is known in the sinusoidal frequency domain. It is given in its final form as a complex function of the angular frequency ω (not jω ). How to obtain the step response?
Thanks in advance.
 
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In order to figure this out you need to know two things:

1. The relationship between the transfer function and the impulse response

2. The relationship between the impulse response and the step response

Hopefully this points you in the correct direction.

jason
 
How would you normally obtain the step response given the transfer function?
Note: If you have ##s=j\omega## - then ##f(\omega) = f(-js)## right?

If you prefer, you can Fourier transform back to time domain, then transfer to frequency domain like you are used to.
 
Dear friends:
Thanks for your kind comments. In the meantime I could find a direct straightforward answer in the 1959 publication:

SIMPLIFED METHOD OF DETERMINING TRANSIENT RESPONSE
FROM FREQUENCY RESPONSE OF LINEAR NETWORKS AND SYSTEMS

By: Victor S . Levadi

Thanks again.
Boudy
 
Excellent - perhaps you could summarize what you found?
 
In order to find the Impulse response , f(t), you need only the real part , R(ω),of the transfer function
F(j ω).
According to the mentioned paper:
f(t)= (2/π).∫R(ω).cos(tω) dω
The limits of integration are from zero to infinity.
Best regards
 
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