Applications of Routh-Hurwitz criterion to evaluation of phase margin and phase lead compensation

A method based on a transformation G(s)=1/2(aG(s)+G(s)^-1) is proposed for applying the Routh-Hurwitz criterion to determine the phase margin of a linear time-invariant feedback control system, and to design phase-lead compensation. A numerical example is also given to illustrate the method.