Published by John Wiley & Sons, Inc., Hoboken, New Jersey.
Published simultaneously in Canada.
No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning, or otherwise, except as permitted under Section 107 or 108 of the 1976 United States Copyright Act, without either the prior written permission of the Publisher, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, (978) 750-8400, fax (978) 750-4470, or on the web at www.copyright.com. Requests to the Publisher for permission should be addressed to the Permissions Department, John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, (201) 748-6011, fax (201) 748-6008, or online at http://www.wiley.com/go/permission.
Limit of Liability/Disclaimer of Warranty: While the publisher and author have used their best efforts in preparing this book, they make no representations or warranties with respect to the accuracy or completeness of the contents of this book and specifically disclaim any implied warranties of merchantability or fitness for a particular purpose. No warranty may be created or extended by sales representatives or written sales materials. The advice and strategies contained herein may not be suitable for your situation. You should consult with a professional where appropriate. Neither the publisher nor author shall be liable for any loss of profit or any other commercial damages, including but not limited to special, incidental, consequential, or other damages.
For general information on our other products and services or for technical support, please contact our Customer Care Department within the United States at (800) 762-2974, outside the United States at (317) 572-3993 or fax (317) 572-4002.
Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic formats. For more information about Wiley products, visit our web site at www.wiley.com
Library of Congress Cataloging-in-Publication Data is available.
ISBN: 978-1-119-05533-4
To
Pam, Bryant, Mason, and Amber
and in memory of my parents
John and Betty Khoo
Preface
It has been 17 years since the publication of the original edition of this monograph. Over this period, I have taught, almost on a yearly basis, a course at the University of Southern California that is based largely on the contents of this book. This second edition incorporates much of the experience I have gained and student feedback I have received from teaching this class. I have also received input from the many instructors who have used this book for their classes. To all these readers, I am deeply appreciative of their helpful comments and questions. The primary goals of this book remain the same as in the first edition: to highlight the basic techniques employed in control theory, systems analysis, and model identification and to give the biomedical engineering student an appreciation of how these principles can be applied to better understand the processes involved in physiological regulation. As before, my assumption is that much of the contents of this second edition are suitable for use in a one-semester course on physiological control systems or physiological systems analysis taken by junior or senior undergraduates or as an introductory class on physiological systems for first-year graduate students. The more advanced parts of this book and its accompanying software may also prove to be a useful resource for biomedical engineers and interested life science or clinical researchers who have had little formal training in systems or control theory. Throughout this book, I have emphasized the physiological applications of control engineering, focusing in particular on the analysis of feedback regulation. In contrast, the basic concepts and methods of control theory are introduced with little attention paid to mathematical derivations or proofs. For this reason, I would recommend the inclusion of a more traditional, engineering-oriented control theory course as a supplement to the material covered in this volume.
One of the main issues I have had with the first edition was the “gap” between the main concepts in systems and control that were introduced assuming continuous-time systems and some of the more advanced applications that featured discrete-time models. Chapter 7 has been introduced to bridge this gap, and to show the reader how continuous-time systems can be converted into discrete-time systems, as well as the impact of different methods of conversion on stability characteristics of the system in question. This additional background should also be useful since many physiological processes (including cardiac, respiratory, and neural) are naturally oscillatory, and models that employ a cycle-by-cycle (and hence, discrete) time base may be more suitable for characterizing longer term dynamics. In Chapter 9, I have revamped what was previously Chapter 8 to cover the essential aspects of time-varying or nonstationary systems. The chapter on physiological system identification (now Chapter 8) has been expanded to include more techniques, such as nonparametric identification using multivariable autoregressive with exogenous (ARX) models and basis function expansion. Finally, the chapter on nonlinear analysis (now Chapter 10) has been expanded to include the Volterra kernel approach to nonparametric estimation of nonlinear systems as well as an introductory discussion of other methods. I have also added material to update various other sections, as well as new problems to the end of each chapter. The MATLAB/SIMULINK files accompanying the book have also been expanded and existing programs have been updated to be compatible with release version R2016b. I see these programs to be an essential complement to the learning experience, allowing the reader to explore “first-hand” the dynamics underlying the biological mechanisms being studied. I do make the implicit assumption that the reader has some basic familiarity with MATLAB/SIMULINK. For the reader who has not used MATLAB or SIMULINK, it is fortunate that there are currently many “primers” on the subject that can be easily found online or in any academic bookstore.
The completion of this second edition has taken much longer than I had anticipated when I took on the project (and I am quite embarrassed to disclose how long ‘long’ is!). I thank Wiley-IEEE Press for giving me the opportunity to produce this second edition, editor Mary Hatcher for her infinite patience, and my friend Metin Akay, the book series editor, for his constant encouragement. This second edition would not have been possible without the feedback and insights gained through my interactions with my past and present Ph.D. students over the years. In particular, I am most grateful to my former student and current research associate, P. “Sang” Chalacheva, who so generously gave her spare time and effort to help with the development of the new MATLAB files and the editing of all parts of this second edition. I would be remiss if I did not also mention the supportive environment provided by the NIH-NIBIB-funded Biomedical Simulations Resource (BMSR), which has funded my research on physiological control and modeling for the past three decades. The modeling activities of my colleagues in the BMSR, David D'Argenio, Vasilis Marmarelis, and Ted Berger, have been a great source of intellectual stimulation over the years. I cannot help but end these remarks by citing my favorite line from the writings of the late Professor Fred Grodins, who recruited me to USC many many moons ago:
“There is nothing magic about Models (or is there?)!”