Ex. PGS 1022
`(EXCERPTED)
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`I I. GTI:I'W
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`Modern
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`Control
` Systems
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`RICHARD C. DORF
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`University of California, Davis
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`ROBERT H. BISI-—lOP A
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`The University of Texas" at Austin
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`y‘y ADDISON-WESLEY
`An imprint of Addison Wesley Longman, Inc.
`
`Menlo Park,
`Berkeley, California - Don
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`'fornia - Reading. Massachusetts - Harlow, England
`' s, Ontario - Sydney - Bonn - Amsterdam - Tokyo - Mexico City
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`EX. PGS 1022
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`Ex. PGS 1022
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`Copyright © 1998 Addison Wesley Longman, Inc.
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`All rights reserved. No part of this publication may be reproduced, or stored in a database or retrieval system, or transmitted, in
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`II. Title.
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`97-6632
`CIP
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`Library of Congress Cataloging-in-Publication Data
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`Dorf, Richard C.
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`Modern control systems / Richard C. Dorf, Robert H. Bishop. — 8th ed.
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`p.
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`Includes bibliographical references and index.
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`ISBN 0—20l —30864—9
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`1. Feedback control systems.
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`TJ216.D67
`1998
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`629.8'3—dc21
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`2. Control theory.
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`1. Bishop, Robert H., 1957-
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`EX. PGS 1022
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`Ex. PGS 1022
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`

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`Chapteril
`
`Introduction to Control Systems
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`»
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`Finally, we introduce the Sequential Design Example": Disk Drive Read System. This
`example will be considered sequentially in each chapter of this book. It represents a very
`important and practical control system design problem while simultaneously serving as _a
`useful learning tool.
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`1.1 INTRODUCTION
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`-
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`Engineering is concerned with understanding and controlling the materials and forces of
`nature for the benefit of humankind. Control system engineers are concerned with under-
`standing and controlling segments of their environment, often called systems, to provide
`useful economic products for society. The twin goals of understanding and control are
`complementary because effective systems control requires that the systems be understood
`and modeled. Furthermore, control engineering must often consider the control of poorly
`understood systems such as chemical process systems. The present challenge to control
`engineers is the modeling and control of modern, complex, interrelated systems such as
`traffic control systems, chemical processes, and robotic systems. Simultaneously, the for-
`tunate engineer has the opportunity to control many very useful and interesting industrial
`automation systems. Perhaps the most characteristic quality of control engineering is the
`opportunity to control machines and industrial and economic processes for the benefit of
`society.
`Control engineering is based on the foundations of feedback theory and linear sys-
`tem analysis, and it integrates the concepts of network theory and communication theory.
`Therefore control engineering is not limited to any engineering discipline but is equally
`applicable to aeronautical, chemical, mechanical, environmental, civil, and electrical engi-
`neering. For example, quite often a control system includes electrical, mechanical, and
`chemical components. Furthennore, as the understanding of the dynamics of business. so-
`cial, and political systems increases, the ability to control these systems will increase also.
`A control system is an interconnection of components forming a system configuration
`that will provide a desired system response. The basis for analysis of a system is the foun-
`dation provided by linear system theory, which assumes a cause—effect relationship for the
`components of a system. Therefore a component or process to be controlled can be repre-
`sented by a block, as shown in Fig. 1.1. The input—output relationship represents the cause-
`and-effect relationship of the process, which in turn represents a processing of the input
`signal to provide an output signal variable, often with a power amplification. An open-loop
`control system utilizes a controller or control actuator to obtain the desired response, as
`shown in Fig. 1.2. An open-loop system is a system without feedback.
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`An open,-loop. control system utilizes an actuating device to control the
`process directly without usingfeedback.
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`F|GURE1.1 '
`Process to be
`controlled.
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`EX. PGS 1022
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`Ex. PGS 1022
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`Section 1.5 Examples of Modern Control Systems
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`~
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`11.
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`Fluid output
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`1
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`Fluid input
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`FIGURE 1.10
`A manual control
`system for
`regulating the level
`of fluid in a tank by
`adjusting the
`output valve. The
`operator views the
`level of fluid
`through a port in
`the side of
`the tank.
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`A basic, manually controlled closed-loop system for regulating the level of fluid in a
`tank is shown in Fig. 1.10. The input is a reference level of fluid that the operator is in-
`structed to maintain. (This reference is memorized by the operator.) The power amplifier is
`the operator, and the sensor is visual. The operator compares the actual level with the de-
`sired level and opens or closes the valve (actuator), adjusting the fluid flow out, to maintain
`the desired level.
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`Other familiar control systems have the same basic elements as the system shown in
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`Fig. 1.9. A refrigerator has a temperature setting or desired temperature, a thermostat to
`measure the actual temperature and the error, and a compressor motor for power amplifi-
`cation. Other examples in the home are the oven, furnace, and water heater. In industry,
`there are speed controls, process temperature and pressure controls, position, thickness,
`composition, and quality controls, among many others [14, 17, 18].
`In its modern usage, automation can be defined as a technology that uses programmed
`commands to operate a given process, combined with feedback of information to determine
`that the commands have been properly executed. Automation is often used for processes
`that were previously operated by humans. When automated, the process can operate with-
`out human assistance or interference. In fact, most automated systems are capable of per-
`forming their functions with greater accuracy and precision, and in less time, than humans
`are able to do. A serniautomated process is one that incorporates both humans and robots.
`For instance, many automobile assembly line operations require cooperation between a
`human operator and an intelligent robot.
`A robot is a computer-controlled machine and involves technology closely associated
`with automation. Industrial robotics can be defined as a particular field of automation in
`which the automated machine (that is, the robot) is designed to substitute for human labor
`[18, 2'7, 33]. Thus robots possess certain humanlike characteristics. Today, the most com-
`mon humanlike characteristic is a mechanical manipulator that is patterned somewhat after
`the human arm and wrist. We recognize that the automatic machine is well suited to some
`tasks, as noted in Table 1.2, and that other tasks are best carried out by humans.
`Another very important application of control technology is in the control of the mod-_
`em automobile [19, 20]. Control systems for suspension, steering, and engine control have
`been introduced. Many new autos have a four-wheel-steering system, as well as an antiskid
`control system.
`A three-axis control system for inspecting individual semiconductor wafers is shown
`in Fig. 1.11. This system uses a specific motor to drive each axis to the desired position in
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`EX. PGS 1022
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`Ex. PGS 1022