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Nyquist Plot & stability

Nyquist Plot & stability

Nyquist Plot & stability

Can any one explain how Nyquist plot is assosciated with predicting Stability of a system

RE: Nyquist Plot & stability

If you have a system with transfer function H(s) and negative feedback loop with function G(s), then overall system is

As can be seen from the equation, the system will blow up when the product G(s)H(s) approaches -1.  If you plot trajectory on the nyquist plot you can see how close it comes to the -1 point. Gain margin is how far below |1| the gain was when angle passed through 180. Phase margin is how much ahead of 180 was the phase when gain decreased through the magnitude |1| circle. Same info can be gained from Bode plot.  There's lot's more that can be said....

RE: Nyquist Plot & stability

Thanks pete,

Further, will u be able to qoute some websites/ URL's for reference



RE: Nyquist Plot & stability

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