finding phase margin on Bode and Nyquist plots

For a nyquist plot, if that particular plot never crosses the unit circle, what would that imply about the phase margin? It's already stable or never stable?

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Yes, exactly.

If you want to know which one it is you have to either go through some rather tedious counting of unstable zeros, or just calculate the transfer function and check the roots.

Ditto for a Bode plot that never has gain = 1.

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Tim Wescott

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