Documento Teoria De Control

PREVIEW

Designing and operating an automated process so that it maintains specifications on profitability, quality, safety, environmental impact, etc., requires a close interaction between experts from different disciplines. These include, for example, computer-, process-, mechanical-, instrumentation- and control-engineers.
Since each of thesedisciplines views the process and its control from a differ-
ent perspective, they have adopted different categories, or elements, in terms of
which they think about the automated system. The computer engineer, for exam-
ple, would think in terms of computer hardware, network infrastructure, operating
system andapplication software. The mechanical engineer would emphasize the
mechanical components from which the process is assembled, whereas the instru-
mentation engineer would think in terms of actuators, sensors and their electrical
wiring.
The control engineer, in turn, thinks of the elements of a control system in terms ofabstract quantities such as signals, systems and dynamic responses. These elements can be further specified by their physical realization, the associated model or their properties (see Table 1).

Tangible examples

Signals set point, control
input, disturban-
ces, measurements,Systems process, controller,
sensors, actuators,

Examples of mathematical Examples of properties
approximation

continuous function, sample- analytic, stochastic, si-
sequence, random process,... nusoidal, standard devi-
ations

differential equations, differ- continuous time, sam-
ence equations, transfer func-pled, linear, nonlinear, tions, state space models, ...
Table 1. Systems and signals in a control loop

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This book emphasizes the control engineer’s perspective of process automation. However, the reader should bear the otherperspectives in mind, since they form essential elements in a holistic view of the subject.
This first part of the book is the first stage of our journey into control engineer-
ing. It gives an introduction to the core elements of continuous time signals and
systems, as well as describing the pivotal role of feedback in control system design.These are the basic building blocks on which the remainder of the development
rests.

Chapter 1

THE EXCITEMENT OF
CONTROL ENGINEERING

1.1 Preview

This chapter is intended to provide motivation for studying control engineering. Inparticular it covers:

• an overview of the scope of control

• historical periods in the development of control theory

• types of control problems

• introduction to system integration

• economic benefits analysis

1.2 Motivation for Control EngineeringFeedback control has a long history which began with the early desire of humans to harness the materials and forces of nature to their advantage. Early examples of control devices include clock regulating systems and mechanisms for keeping wind-mills pointed into the wind.
A key step forward in the development of control occurred during the industrial...