ABSTRACT
Root locus analysis was first developed by W. R. Evans as a means of determining the set of positions of the poles of a closed-loop system transfer function as a scalar parameter of the system varies over the interval from –∞ to ∞. The compensator poles and zeros are chosen to shape the branches of the root locus. By displaying the closed-loop poles, the root locus analysis complements the frequency-domain methods, which provide information on the magnitude and phase of the system frequency response. The intuition and understanding that attend the ability to sketch the root locus by hand and the use of the computer for precise root locus calculations are complementary tools in feedback control design. If the branches of the root locus of a given system lie too far to the right, they could be moved to the left if it were possible to introduce an additional zero to the open-loop transfer function.
