Bringing root locus to the classroom

Fifty years ago, on 30 September 1954, the McGraw-Hill Company published Control-System Dynamics by Walter R. Evans as the 40th entry in its popular "Electrical and Electronic Engineering Series." Six years earlier Evans had helped usher in a revolution in the practice of servomechanism design with his root-locus method. Engineers trained in its use were able to shape the dynamic responses of their servo designs starting from the poles and zeroes of their characteristic equations. Engineering educators would need a new textbook to describe the method to their students. With Control-System Dynamics, Evans sought to satisfy that need with a book emphasizing the physical picture over mathematical formalisms. Its development took him on a journey over a road less traveled.