The Nyquist stability criterion ushers the advanced student into a truly deep understanding of feedback theory. To master this concept, a student needs two tools from the mathematics of complex analysis: conformal mapping and Cauchy's principle of the argument. In keeping with the goal of making this guide completely self-contained, a few pages of Chapter 4 are devoted to these topics.Afterward, we dive fully into theNyquist criterion and show how it relates to phase margin. A few examples of Nyquist plots (using Bode plots as a guide) are also given in this chapter.

The purpose of this chapter is to further ground feedback theory in real applications with which thereader already has a great deal of real-world experience. The first section of this chapter deals with a cooling system for a room, and the second section treats the howling public address system.

This is a book about classical feedback control, complete with a review of the linear system theory that can be a stumbling block for many interested in feedback. The author had four groups of people in mind when writng this book.The first group comprises struggling undergraduates who despair of moving forward because too many things simply do not make any conceptual sense. The second group are the star test takers who find that they must put all that they learned out of their heads and rely on an entirely different set of skills to build physical systems, and who wonder why this is. The third group are the young graduate students preparing for their doctoral qualifying exams and find that a deeper level of insight is called for than was needed in their undergraduate years. And the final group are the successful professional practitioners who have made themselves very effective despite a secret unease with the physical foundations of their field.If you fall into one or more of these categories, or if you are simply curious, this book is for you.