How Can I Determine the Equivalent Transfer Function of Two Active LTI Systems?

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Discussion Overview

The discussion revolves around determining the equivalent transfer function of two active linear time-invariant (LTI) systems, G1(s) and G2(s), that operate at different times. Participants explore the implications of switching between these systems and the challenges in representing them with a single transfer function.

Discussion Character

  • Debate/contested, Conceptual clarification

Main Points Raised

  • One participant, Umat, inquires about methods to derive an equivalent transfer function for two LTI systems that are active at different times.
  • Another participant suggests that since G1 and G2 are never active simultaneously, it may not be possible to describe the system with a single transfer function.
  • A different participant notes that switching between the two systems implies the joint system is no longer time-invariant, indicating that the situation is likely more complex than a straightforward combination.
  • Another participant agrees with the notion that a transfer function cannot be defined for a non-LTI system, suggesting alternative descriptions may be necessary.

Areas of Agreement / Disagreement

Participants express differing views on the feasibility of deriving a single equivalent transfer function, with some agreeing on the complexity introduced by switching and the non-LTI nature of the combined system.

Contextual Notes

The discussion highlights the limitations of applying LTI system principles when dealing with systems that are not active simultaneously, and the implications of time-variance in the context of transfer functions.

Who May Find This Useful

Individuals interested in control systems, signal processing, and the theoretical aspects of linear time-invariant systems may find this discussion relevant.

umarkhan
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hello,
If I have two LTI system in G1(s) and G2(s) and I know that for a certain fraction of the time period G1 is active and for the reminaing fraction G2 is active, then is there any method to get the equivalent transfer function ?


Umat.
 
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I would think you would just have two transfer functions. Since there G1 and G2 are never active at the same time, you can't really describe it that way. At least, I don't think there is a way. Maybe I'm wrong though.
 
If you're switching between the two systems, the joint system is no longer time-invariant. It's probably going to be not so simple.
 
I agree with Manchot. And since you can't have a transfer function for a non-LTI system, you'll have to describe it some other way.
 

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