An automatic root locus plotter using an analog computer

THE METHOD of plotting the locus of roots of the characteristic equation of a linear feedback control system has been essentially a manual point-by-point calculation. The basic principles for plotting the root locus were first developed by Evans. The details for analytically calculating some portions of the curves and the procedures for finding points on the curves by a trial-and-error procedure are found in many books in the area of feedback controls. One source for this material is reference 1. It is also possible to calculate points on the root locus by equations developed in reference 2. These equations can be set up on a digital computer, if one is available.