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The root-locus method

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:

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


Module prerequisites. Stability, closed loop, transfer function, poles and zeros.



Subsections

Next: Introduction and basic ideas Up: Course on Dynamics of Previous: The Nyquist criterion using   Contents
Christian Schmid 2005-05-09