Simulink bode diagram loop transfer with negative feedback

Question

Rasmus Steffensen 2019-8-19

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/476688-simulink-bode-diagram-loop-transfer-with-negative-feedback

编辑： Enrique Babio 2021-6-11

Hi,

I am using the bode plot block in simulink, and want to get the open loop transfer function using the 'Loop transfer' configuration. The problem is that it returns the transfer function with positive feedback, and not the one with negative feedback. I.e. i want to as with the matlab equivalent function 'L = getLoopTransfer(T,Locations,sign)' to specify the sign to -1. Is it possible?

kind regards,

Rasmus.

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Answer 1

Nikhil Sonavane 2019-8-22

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https://ww2.mathworks.cn/matlabcentral/answers/476688-simulink-bode-diagram-loop-transfer-with-negative-feedback#answer_388627

You may refer to the tutorial video for more information on how to get the open loop transfer function.

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Enrique Babio 2021-6-11

编辑：Enrique Babio 2021-6-11

Sure, the approach in the video works, but it defeats some of the the purpose of having the 'loop transfer' linearization setting available. That setting would seem the most useful for getting open loop transfer functions on the go from the closed loop diagram that already includes the negative feedback. See your own tutorial: analysis points

For example, I could set the 'loop transfer' point at an actuator model and then I get the margins at this point as a way to determine robustness against changes in its closed loop transfer function. What use cases does the current implementation address?

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