Glossary of Control Engineering Terms - N

Nonlinear System: A system that is not linear!

Non-minimum Phase: A non-minimum phase system has the characteristic that when the reference moves in one direction the output initially moves in the opposite direction before following the reference. Such a system has a zero in the right half plane which are typically caused by the effects of competing slow and fast dynamics.

Nichols Chart: A plot of magnitude against phase for a frequency response. Used in AFT control design.

Nyquist Diagram: An alternative representation of the information in a Bode diagram. The frequency response is a locus in the complex plane with frequency being a parameter on the locus.