The Nyquist Stability Criterion

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The Nyquist stability criterion one of the most fundamental results in control theory: This criterion allows us to predict stability properties of a system after we introduce feedback, before we actually introduce the feedback! In this video we introduce and derive the Nyquist stability criterion using the argument principle.

The Nyquist criterion has far reaching consequence. It not only makes predictions about engineered systems, but can also provide insight in wide range of other contexts. Here we have a quick look at disease spread and delays.