Root locus methods for analysis and design

Abstract

Root locus methods allow study of the changes in the roots of a polynomial as a parameter varies: their implicit but important message is that these roots vary in a regular manner as a parameter varies. Root locus methods are applied to the denominator polynomials of closed-loop transfer functions and hence indicate the movement of system poles as a parameter (typically a control compensator parameter such as a gain) varies. The techniques are independent of whether the system is discrete time or continuous time, but the criteria for good and bad poles depend upon that fact (Chapter 19).