Nyquist Analysis and Stability

Abstract

The analysis of control systems with feedback may also be carried out using a method based on frequency response. The essence of this method, often referred to as a Nyquist plot, is a graphical procedure for determining absolute and relative stability of closed-loop control systems. Information about stability is available directly from a polar plot of the sinusoidal open-loop transfer function G(jω)H(jω), once the feedback system has been reduced to standard form.