Page 54 - Modern Control Systems

Chapter 1 Introduction to Control Systems

revolution in computer technology is causing an equally momentous social change,
the expansion of information gathering and information processing as computers
extend the reach of the human brain [16].
Control systems are used to achieve (1) increased productivity and (2) improved
performance of a device or system. Automation is used to improve productivity and
obtain high-quality products. Automation is the automatic operation or control of a
process, device, or system. We use automatic control of machines and processes to
produce a product reliably and with high precision [28]. With the demand for flexible,
custom production, a need for flexible automation and robotics is growing [17,25].
The theory, practice, and application of automatic control is a large, exciting,
and extremely useful engineering discipline. One can readily understand the moti-
vation for a study of modern control systems.

EXAMPLES

In this section we present illustrative design examples. This is a pattern that we will
follow in all subsequent chapters. Each chapter will contain a number of interesting
examples in a special section entitled Design Examples meant to highlight the main
topics of the chapter. At least one example among those presented in the Design Ex-
ample section will be a more detailed problem and solution that demonstrates one or
more of the steps in the design process shown in Figure 1.17. In the first example, we
discuss the development of the smart grid as a concept to deliver electrical power
more reliably and efficiently as part of a strategy to provide a more environmentally
friendly energy delivery system. The smart grid will enable the large-scale use of re-
newable energy sources that depend on the natural phenomenon to generate power
and which are intermittent, such as wind and solar. Providing clean energy is an engi-
neering challenge that must necessarily include active feedback control systems, sen-
sors, and actuators. In the second example presented here, a rotating disk speed
control illustrates the concept of open-loop and closed-loop feedback control. The
third example is an insulin delivery control system in which we determine the design
goals, the variables to control, and a preliminary closed-loop system configuration.

EXAMPLE 1.4 Smart grid control systems
A smart grid is as much a concept as it is a physical system. In essence, the concept is
to deliver power more reliably and efficiently while remaining environmentally
friendly, economical, and safe [89,90]. A smart grid can be viewed as a system com-
prised of hardware and software that routes power more reliably and efficiently to
homes, businesses, schools, and other users of power. One view of the smart grid is il-
lustrated schematically in Figure 1.23. Smart grids can be national or local in scope.
One can even consider home smart grids (or microgrids). In fact, smart grids en-
compass a wide and rich field of investigation. As we will find, control systems play
a key role in smart grids at all levels.
One interesting aspect of the smart grid is real-time demand side management re-
quiring a two-way flow of information between the user and the power generation sys-
tem [91]. For example, smart meters are used to measure electricity use in the home
and office. These sensors transmit data to utilities and allow the utility to transmit
control signals back to a home or building. These smart meters can control and turn on