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{{chheader|Main Page|Preface|Introduction}}
This section contains the front matter for the book, including the title page, preface and table of contents.  We also collect here some links that may be useful for instructors who are planning to use this book for a course.  The preface of the book is presented in its entirety below, with some additional markup to link to the material in this wiki.

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== Textbook Contents ==
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* Titlepage and Copyright
* Preface
* Table of Contents

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== Teaching Materials ==
* [[Information for instructors]]
* [[Course syllabus suggestions]]

== Supplemental Information ==
* [[#Frequently Asked Questions|Frequently Asked Questions]]
* [[#Errata|Errata]]
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== Preface ==

This book provides an introduction to the basic principles and tools for design and analysis of feedback systems. It is intended to serve a diverse audience of scientists and engineers who are interested in understanding and utilizing feedback in physical, biological, information, and economic systems. To this end, we have chosen to keep the mathematical prerequisites to a minimum while being careful not to sacrifice rigor in the process.  Advanced sections, marked by the "dangerous bend" symbol [[Image:dbend.gif|right]] shown to the  right, contain material that is of a more advanced nature and can be skipped on first reading. 

This book was originally developed for use in an experimental course at 
Caltech involving students from a wide variety of disciplines. The course 
consisted of undergraduates at the junior and senior level in traditional engineering disciplines, as well as first and second year graduate students in 
engineering and science. This included graduate students in biology, computer science and economics, requiring a broad approach that emphasized 
basic principles and did not focus on applications in any one given area. 
A detailed web site has been prepared as a companion to this text: 

 http://www.cds.caltech.edu/~murray/amwiki

The web site contains a database of frequently asked questions, supplemental 
examples and exercises, and lecture materials for a course based on this text. 
It also contains the MATLAB and other source code for every example in the 
book, as well as MATLAB libraries to implement the techniques described 
in the text. 

=== Textbook scope ===

This book is intended to serve a broad spectrum of audiences and is 
organized in a slightly unusual fashion compared to many other books on 
feedback and control. In particular, we introduce a number of concepts in 
the text that are normally reserved for second year courses on control (and 
hence often not available to students who are not control systems majors). 

This has been done at the expense of certain "traditional" topics, which 
we felt that the astute student could learn on their own (and are often 
explored through the exercises). Examples of topics that we have included 
are nonlinear dynamics, Lyapunov stability, reachability and observability, 
and fundamental limits of performance and robustness. Topics that we 
have de-emphasized include root locus techniques, lead/lag compensation 
(although this is essentially covered in Chapters 10 ([[PID Control]]) and 11 ([[Loop Shaping]]), and detailed 
rules for generating Bode and Nyquist plots by hand.

=== Overview of the contents ===

The first half of the book focuses almost exclusively on so-called "state-space" control systems. We begin in Chapter 2 ([[System Modeling]]) with a description of modeling of physical, biological and information systems using ordinary differential equations and difference equations. Chapter 3 ([[Examples]]) presents a number of 
examples in some detail, primarily as a reference for problems that will be 
used throughout the text. Following this, Chapter 4 ([[Dynamic Behavior]]) looks at the dynamic 
behavior of models, including definitions of stability and more complicated 
nonlinear behavior. We provide advanced sections in this chapter on Lyapunov stability, because we find that it is useful in a broad array of applications (and frequently a topic that is not introduced until much later in one's 
studies). 

The remaining three chapters of the first half of the book focus on linear 
systems, begining with a description of input/output behavior in Chapter 5 ([[Linear Systems]]). 
In Chapter 6 ([[State Feedback]]), we formally introduce feedback systems by demonstrating how 
state space control laws can be designed. This is followed in Chapter 7 ([[Output Feedback]]) by 
material on output feedback and estimators. Chapters 6 and 7 introduce 
the key concepts of reachability and observability, which give tremendous 
insight into the choice of actuators and sensors, whether for engineered or 
natural systems. 

The second half of the book presents material that is often considered to 
be from the field of "classical control." This includes the transfer function, 
introduced in Chapter 8 ([[Transfer Functions]]), which is a fundamental tool for understanding 
feedback systems. Using transfer functions, one can begin to analyze the 
stability of feedback systems using loop analysis, which allows us to reason 
about the closed loop behavior (stability) of a system from its open loop 
characteristics. This is the subject of Chapter 9 ([[Loop Analysis]]), which revolves around the 
Nyquist stability criterion. 

In Chapters 10 ([[PID Control]]) and 11 ([[Loop Shaping]]), we again look at the design problem, focusing first 
on proportional-integral-derivative (PID) controllers and then on the more 
general process of loop synthesis. PID control is by far the most common 
design technique in control systems and a useful tool for any student. The 
chapter on loop synthesis introduces many of the ideas of modern control
theory, including the sensitivity function. In Chapter 12 ([[Robust Performance]]), we pull together 
the results from the second half of the book to analyze the fundamental 
tradeoffs between robustness and performance. This is also a key chapter 
illustrating the power of the techniques that have been developed.

=== Use in courses ===

The book is designed for use in a 10-15 week course in feedback systems 
that can serve to introduce many of the key concepts that are needed in 
a variety of disciplines. For a 10 week course, Chapters 1-6 and 8-11 can 
each be covered in a week's time, with some dropping of topics from the 
final chapters. A more leisurely course, spread out over 14-15 weeks, could 
cover the entire book, with two weeks on modeling (Chapter 2) -- particularly 
for students without much background in ordinary differential equations --  
and two weeks on loop analysis (Chapter 9) or robustness and performance 
(Chapter 12). 

In choosing the set of topics and ordering for the main text, we necessarily left out some tools which will cause many control systems experts to 
raise their eyebrows (or choose another textbook). Overall, we believe that 
the early focus on state space systems, including the concepts of reachability 
and observability, are of such importance to justify trimming other topics to 
make room for them. We also included some relatively advanced material 
on fundamental tradeoffs and limitations of performance, feeling that these 
provided such insight into the principles of feedback that they could not 
be left for later. Throughout the text, we have attempted to maintain a 
balanced set of examples that touch many disciplines, relying on the supplements for more discipline specific examples and exercises. Additional notes 
covering some of the "missing" topics are available on the web. 

One additional choice that we felt was very important was the decision 
not to make use of Laplace transforms in this book. While this is by far the 
most common approach to teaching feedback systems in engineering, many 
students in the natural and information sciences may lack the necessary 
mathematical background. Since Laplace transforms are not required in 
any essential way, we have only made a few remarks to tie things together 
for students with that background. Of course, we make tremendous use of 
transfer functions, which we introduce through the notion of response to 
exponential inputs, an approach we feel is much more accessible to a broad 
array of scientists and engineers.

=== Acknowledgments === 
The authors would like to thank the many people who helped during the 
preparation of this book. The idea for writing this book came in part from a 
report on future directions in control {{bibcite|Mur03}} to which Stephen Boyd, Roger 
Brockett, John Doyle and Gunter Stein were ma jor contributers. Kristi 
Morgenson and Hideo Mabuchi helped teach early versions of the course at 
Caltech on which much of the text is based and Steve Waydo served as the 
head TA for the course taught at Caltech in 2003-04 and provide numerous 
comments and corrections.  Finally, we would like to thank Caltech, Lund University and 
the University of California at Santa Barbara for providing many resources, 
stimulating colleagues and students, and a pleasant working environment 
that greatly aided in the writing of this book. 

<br>
{| width=100% cellpadding=0 cellspacing=0
|- valign=top
| width=10% |
| width=40% align=left | Karl Johan {{Astrom}}
| width=40% align=right | Richard M. Murray
| width=10% | 
|-
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| align=left | Lund, Sweden 
| align=right | Pasadena, California
|
|}
<br>

== Frequently Asked Questions ==
<ncl>Preface FAQ</ncl>
== Errata ==
<ncl>Preface errata v2.11b</ncl>
* [[:Category:Preface errata|Full list of errata starting from first printing]]
* {{submitbug}}
== Additional Information ==
* [[AMwiki:About|About AMwiki]] - more information on this wiki