Open loop transfer function help

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Discussion Overview

The discussion revolves around determining the open loop transfer function for a system represented by a block diagram. Participants are exploring definitions, derivations, and methods related to open loop transfer functions, with a focus on understanding the components involved.

Discussion Character

  • Homework-related
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant expresses confusion about the definition of open loop transfer function, noting discrepancies in sources and mentioning the equation G*H.
  • Another participant questions whether the original poster understands which elements determine the transfer function in an open loop scenario.
  • A different participant suggests a specific formula for the open loop transfer function but admits uncertainty about its derivation.
  • One participant challenges the correctness of the proposed formula and offers a method for measuring or simulating the gain of the open loop, emphasizing the simplicity and logic of the process.

Areas of Agreement / Disagreement

Participants do not appear to reach a consensus on the correct open loop transfer function or the method for deriving it. Multiple viewpoints and methods are presented, indicating ongoing debate and uncertainty.

Contextual Notes

There are limitations in the clarity of the definitions and the derivation process for the open loop transfer function, as well as potential dependencies on specific system configurations that are not fully detailed in the discussion.

axe34
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Homework Statement


upload_2016-4-3_15-17-16.png
[/B]
I need to work out the open loop transfer function of the above. I've drawn it on word so it's not great; the + and - represent a summing junction.

Homework Equations


Everywhere I read, I find a different definition of open loop transfer function. I see G*H is an oft used equation but I'm not sure...[/B]

The Attempt at a Solution


None!
 
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Your drawing contains a loop of several blocks, correct?
Do you really have no idea which elements/blocks determine the transfer function of the loop under open conditions?
 
No I do not.
 
KpKaGcGp / (n + KpkaGcGp) is the answer supposedly but I don't know how this was derived.
 
axe34 - no, it is not correct.
Here is the procedure for measureing/simulating the gain of the open loop.
You have nothing to do than to open the loop (at any place you like), to inject a test signal and to find the output at the other side of the opening.
And this procedure gives you the method also for calculating the gain within the complete loop. It is easier as you might think - and it is quite logical!.
 

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