Research on Teaching Method for Nyquist Stability Criterion of Linear Control System

The method of frequency analysis of linear control system is an important part in automation control theory studying,and Nyquist stability criterion is one of the focuses on teaching content.In order to improve students understanding of the concept,the contents of the error-prone carry out details explaining in definition of Nyquist stability criterion,drawing the curve of amplitude and phase frequency characteristics diagram for open-loop system,and drawing the diagram of open-loop poles on the imaginary axis and determine of stability.The determination of starting phase angle point and end phase angle point in the Nyquist mapping is analyzed.How to draw the supplement curve is also given by a comprehensive summary and are described with examples.