Panos J. Antsaklis
Anthony N. Michel
A Linear Systems Primer
Birkh¨auser
Boston • Basel • Berlin
Panos J. Antsaklis
Department of Electrical Engineering
University of Notre Dame
Notre Dame, IN 46556
U.S.A.
Anthony N. Michel
Department of Electrical Engineering
University of Notre Dame
Notre Dame, IN 46556
U.S.A.
Cover design by Mary Burgess.
Mathematics Subject Classification (2000): 34A30, 34H05, 93-XX, 93-01, 93Axx, 93A30, 93Bxx,
93B03, 93B05, 93B07, 93B10, 93B11, 93B12, 93B15, 93B17, 93B18, 93B20, 93B25, 93B50, 93B55,
93B60, 93Cxx, 93C05, 93C15, 93C35, 93C55, 93C57, 93C62, 93Dxx, 93D05, 93D15, 93D20, 93D25,
93D30
Library of Congress Control Number: 2007905134
ISBN-13: 978-0-8176-4460-4
e-ISBN-13: 978-0-8176-4661-5
Printed on acid-free paper.
c2007 Birkh ¨auser Boston
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(MP)
To our Families
To
Melinda and our daughter Lily
and to my parents
Dr. Ioannis and Marina Antsaklis
—Panos J. Antsaklis
To
Leone and our children
Mary, Kathy, John,
Tony, and Pat
—Anthony N. Michel
And to our Students
Preface
Brief Description
The purpose of this book is to provide an introduction to system theory with
emphasis on control theory. It is intended to be the textbook of a typical
one-semester course introduction to systems primarily for first-year graduate
students in engineering, but also in mathematics, physics, and the rest of the
sciences. Prerequisites for such a course include undergraduate-level differ-
ential equations and linear algebra, Laplace transforms, and modeling ideas
of, say, electric circuits and simple mechanical systems. These topics are typi-
cally covered in the usual undergraduate curricula in engineering and sciences.
The goal of this text is to provide a clear understanding of the fundamental
concepts of systems and control theory, to highlight appropriately the princi-
pal results, and to present material sufficiently broad so that the reader will
emerge with a clear picture of the dynamical behavior of linear systems and
their advantages and limitations.
Organization and Coverage
This primer covers essential concepts and results in systems and control the-
ory. Since a typical course that uses this book may serve students with different
educational experiences, from different disciplines and from different educa-
tional systems, the first chapters are intended to build up the understanding
of the dynamical behavior of systems as well as provide the necessary mathe-
matical background. Internal and external system descriptions are described
in detail, including state variable, impulse response and transfer function,
polynomial matrix, and fractional representations. Stability, controllability,
observability, and realizations are explained with the emphasis always being
on fundamental results. State feedback, state estimation, and eigenvalue as-
signment are discussed in detail. All stabilizing feedback controllers are also
parameterized using polynomial and fractional system representations. The
emphasis in this primer is on time-invariant systems, both continuous and
viii
Preface
discrete time. Although time-varying systems are studied in the first chapter,
for a full coverage the reader is encouraged to consult the companion book
titled Linear Systems 1 that offers detailed descriptions and additional mate-
rial, including all the proofs of the results presented in this book. In fact, this
primer is based on the more complete treatment of Linear Systems, which
can also serve as a reference for researchers in the field. This primer focuses
more on course use of the material, with emphasis on a presentation that is
more transparent, without sacrificing rigor, and emphasizes those results that
are considered to be fundamental in systems and control and are accepted as
important and essential topics of the subject.
Contents
In a typical course on Linear Systems, the depth of coverage will vary de-
pending on the goals set for the course and the background of the students.
We typically cover the material in the first three chapters in about six to
seven weeks or about half of the semester; we spend about four to five weeks
covering Chapters 4–8 on stability, controllability, and realizations; and we
spend the remaining time in the course on state feedback, state estimation,
and feedback control presented in Chapters 9–10. This book contains over 175
examples and almost 160 exercises. A Solutions Manual is available to course
instructors from the publisher. Answers to selected exercises are given at the
end of this book.
By the end of Chapter 3, the students should have gained a good under-
standing of the role of inputs and initial conditions in the response of systems
that are linear and time-invariant and are described by state-variable inter-
nal descriptions for both continuous- and discrete-time systems; should have
brushed up and acquired background in differential and difference equations,
matrix algebra, Laplace and z transforms, vector spaces, and linear transfor-
mations; should have gained understanding of linearization and the generality
and limitations of the linear models used; should have become familiar with
eigenvalues, system modes, and stability of an equilibrium; should have an
understanding of external descriptions, impulse responses, and transfer func-
tions; and should have learned how sampled data system descriptions are
derived.
Depending on the background of the students, in Chapter 1, one may want
to define the initial value problem, discuss examples, briefly discuss existence
and uniqueness of solutions of differential equations, identify methods to solve
linear differential equations, and derive the state transition matrix. Next, in
Chapter 2, one may wish to discuss the system response, introduce the impulse
response, and relate it to the state-space descriptions for both continuous-
and discrete-time cases. In Chapter 3, one may consider to study in detail
the response of the systems to inputs and initial conditions. Note that it is
1 P.J. Antsaklis and A.N. Michel, Linear Systems, Birkh¨auser, Boston, MA, 2006.
Preface
ix
possible to start the coverage of the material with Chapter 3 going back to
Chapters 1 and 2 as the need arises.
A convenient way to decide the particular topics from each chapter that
need to be covered is by reviewing the Summary and Highlights sections at
the end of each chapter.
The Lyapunov stability of an equilibrium and the input/output stability
of linear time-invariant systems, along with stability, controllability and ob-
servability, are fundamental system properties and are covered in Chapters 4
and 5. Chapter 6 describes useful forms of the state space representations such
as the Kalman canonical form and the controller form. They are used in the
subsequent chapters to provide insight into the relations between input and
output descriptions in Chapter 7. In that chapter the polynomial matrix rep-
resentation, an alternative internal description, is also introduced. Based on
the results of Chapters 5–7, Chapter 8 discusses realizations of transfer func-
tions. Chapter 9 describes state feedback, pole assignment, optimal control,
as well as state observers and optimal state estimation. Chapter 10 character-
izes all stabilizing controllers and discusses feedback problems using matrix
fractional descriptions of the transfer functions.
Depending on the interest and the time constraints, several topics may be
omitted completely without loss of continuity. These topics may include, for
example, parts of Section 6.4 on controller and observer forms, Section 7.4 on
poles and zeros, Section 7.5 on polynomial matrix descriptions, some of the
realization algorithms in Section 8.4, sections in Chapter 9 on state feedback
and state observers, and all of Chapter 10.
The appendix collects selected results on linear algebra, fields, vector
spaces, eigenvectors, the Jordan canonical form, and normed linear spaces,
and it addresses numerical analysis issues that arise when computing solu-
tions of equations.
Simulating the behavior of dynamical systems, performing analysis us-
ing computational models, and designing systems using digital computers,
although not central themes of this book, are certainly encouraged and often
required in the examples and in the Exercise sections in each chapter. One
could use one of several software packages specifically designed to perform
such tasks that come under the label of control systems and signal processing,
and work in different operating system environments; or one could also use
more general computing languages such as C, which is certainly a more te-
dious undertaking. Such software packages are readily available commercially
and found in many university campuses. In this book we are not endorsing any
particular one, but we are encouraging students to make their own informed
choices.
Acknowledgments
We are indebted to our students for their feedback and constructive sugges-
tions during the evolution of this book. We are also grateful to colleagues
x
Preface
who provided useful feedback regarding what works best in the classroom in
their particular institutions. Special thanks go to Eric Kuehner for his expert
preparation of the manuscript. This project would not have been possible
without the enthusiastic support of Tom Grasso, Birkh¨auser’s Computational
Sciences and Engineering Editor, who thought that such a companion primer
to Linear Systems was an excellent idea. We would also like to acknowledge
the help of Regina Gorenshteyn, Associate Editor at Birkh¨auser.
It was a pleasure writing this book. Our hope is that students enjoy reading
it and learn from it. It was written for them.
Notre Dame, IN
Spring 2007
Panos J. Antsaklis
Anthony N. Michel