Nyquist plot
A Nyquist plot is used in automatic control and signal processing for assessing the stability of a system with feedback. It is represented by a graph in polar coordinates in which the gain and phase of a frequency response are plotted. The plot of these phasor quantities shows the phase as the angle and the magnitude as the distance from the origin. This plot combines the two types of Bode plot — magnitude and phase — on a single graph, with frequency as a parameter along the curve. The Nyquist plot is named after Harry Nyquist, a former engineer at Bell Laboratories.
The high frequency response is at the origin, corresponding to high frequencies being attenuated (high-cut/low-pass filter). The plot provides information on the poles and zeros of the transfer function[1] (e.g. from the angle at which the curve approaches the origin).
Assessment of the stability of a closed-loop negative feedback system hjhua feedback loop.
See also
- Argument principle
- BIBO stability
- Nichols plot
- Randles circuit
- Electrochemical impedance spectroscopy
References
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