An Improved Method with Bode diagram as to System Stability Analysis

System stability analysis is an important and difficult matter in the automatic control theory.In theaching materials,the Nyquist criterion is ofen used to juge system stability,in this way,one method is polar plots of frequncy characteristics(Nyquist diagram),another is the logarithm diagram of frequncy characteristics(Bode diagram).But these two methods all require their respective frequency characteristic curve,which means lots of calculation and complicated drawing.So these two methods are very difficult for students.In order to resolve this problem,this paper provide an analytic method based on the bode diagram.