**Module overview.**
*Based on the pole and zero distributions of an open-loop
system the stability of the closed-loop system can be discussed as
a function of one scalar parameter. The root-locus method shown in this
module is a technique that can be used as a tool to design control
systems. The basic ideas and its relevancy to control system
design are introduced and illustrated. Ten general rules for
constructing root loci for positive and negative gain are shortly
presented such that they can be easily applied. This is
demonstrated by some discussed examples, by a table with sixteen
examples and by a comprehensive design of a closed-loop system of
higher order. *

**Module objectives.**
*When you have completed this module you should be able
to:*

- Understand root-locus diagrams.
- Draw root-locus diagrams.
- Apply the root-locus method to design control systems.
- Discuss the stability of closed-loop systems with respect to variations in one parameter.

- Introduction and basic ideas
- General rules for constructing root loci
- Example of an application of the root-locus method