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[Solved] How do you use rlocus with multiple feedback loops?

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Joseph Patrick
Joseph Patrick on 19 Apr 2021 at 16:59
Edited: Joseph Patrick on 20 Apr 2021 at 15:19
So I have this control loop and I want to plot the root locus with the gain variable Kt but I how do you do this as rlocus expects a single feedback loop, not two where one is affected by the gain and the other is not?

Answers (1)

Paul
Paul on 19 Apr 2021 at 22:30
Start with the correct characteristic equation:
1 + D(s)*G(s)*I(s) + D(s)*G(s)*Kt = 0 (not sure why the picture shows the last term divided by I(s) ).
Let L(s) be the "loop transfer function" that should be used to plot the root locus with respect to Kt. What is the CE written in terms of L(s) and Kt? Can the actual CE be manipulated into that form?
  6 Comments
Joseph Patrick
Joseph Patrick on 20 Apr 2021 at 15:14
Yeah, managed to get my plot
Thanks for the help :)

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