Preface

From the late 70s we have witnessed a revolution in the field of control, when it was found that the classical and modern control theories did not assure the stability or performance of the system under uncertainty.

Due to the need of being tolerant to changes in the control systems, subject to unknown dis‐ turbances or random changes in the operational environment of these systems, the robust control theory started generating new methods that are able to deal with the non-parameter‐ ized disturbances of systems, without adapting itself to the system uncertainty, but rather providing stability in the presence of errors bound to a model or dealing directly and effec‐ tively with real parameters uncertainty in the control systems.

Robust control applications have been increasing from the mid-80s with the Kharitonov's Theorem for interval polynomials; after this, several applications in aerospace, electrical, mechanical and others fields have been generated. More recently, Hansen and Sargent intro‐ duced an approach in the field of economics, which the solution of robustness problem is found implementing a dynamic game.

We could say, that in the last two decades, several questions about stability of systems un‐ der uncertainty have been answered. However, the robustness problem will remain a study subject, to improve the technological development and enhance the human quality of life in the world.

With this approach in mind and with the intention to exemplify robust control applications, this book includes selected chapters that describe models of H-infinity loop-shaping, robust stability and uncertainty, among others.

Each robust control method and model discussed in this book is illustrated by a relevant example, which facilitates its use as research reference or practical textbook in graduate pro‐ grams.

Finally, we are grateful to the authors for their kind contributions and also appreciate the publisher for the support and guidance to publish this book.

> **Moises Rivas López** Engineering Institute Autonomous University of Baja California, Mexico

> **Wendy Flores-Fuentes** Faculty of Engineering Autonomous University of Baja California, Mexico
