Modern Control Systems
TWELFTH EDITION
Richard C. Dorf University of California
Davis Robert H. Bishop Marquette University
MODERN CONTROL SYSTEMS—THE BOOK
Global issues such as climate change, clean water, sustainability, waste management
emissions reduction, and minimizing raw material and energy use have caused many
engineers to re-think existing approaches to engineering design. One outcome of
the evolving design strategy is to consider green engineering.The goal of green engineering
is to design products that minimize pollution, reduce the risk to human
health, and improve the environment. Applying the principles of green engineering
.highlights the power of feedback control systems as an enabling technology
To reduce greenhouse gases and minimize pollution, it is necessary to improve
both the quality and quantity of our environmental monitoring systems. One example
is to use wireless measurements on mobile sensing platforms to measure the
external environment. Another example is to monitor the quality of the delivered
.power to measure leading and lagging power, voltage variations, and waveform harmonics
Many green engineering systems and components require careful monitoring
of current and voltages. For example, current transformers are used in various
capacities for measuring and monitoring current within the power grid network of
interconnected systems used to deliver electricity. Sensors are key components of
any feedback control system because the measurements provide the required information
as to the state of the system so the control system can take the appropriate
.action
The role of control systems in green engineering will continue to expand as the
global issues facing us require ever increasing levels of automation and precision. In
the book, we present key examples from green engineering such as wind turbine
control and modeling of a photovoltaic generator for feedback control to achieve
.maximum power delivery as the sunlight varies over time
.The wind and sun are important sources of renewable energy around the world
Wind energy conversion to electric power is achieved by wind energy turbines connected
to electric generators. The intermittency characteristic of the wind makes
smart grid development essential to bring the energy to the power grid when it is
available and to provide energy from other sources when the wind dies down or is
disrupted. A smart grid can be viewed as a system comprised of hardware and software
that routes power more reliably and efficiently to homes, businesses, schools
.and other users of power in the presence of intermittency and other disturbances
The irregular character of wind direction and power also results in the need for reliable
.steady electric energy by using control systems on the wind turbines themselves
The goal of these control devices is to reduce the effects of wind
intermittency and the effect of wind direction change. Energy storage systems are
also critical technologies for green engineering. We seek energy storage systems that
are renewable, such as fuel cells. Active control can be a key element of effective
.renewable energy storage systems as well
Control engineering is an exciting and a challenging field. By its very nature, control
engineering is a multidisciplinary subject, and it has taken its place as a core
course in the engineering curriculum. It is reasonable to expect different approaches
to mastering and practicing the art of control engineering. Since the subject has a
strong mathematical foundation, we might approach it from a strictly theoretical
point of view, emphasizing theorems and proofs. On the other hand, since the ultimate
objective is to implement controllers in real systems, we might take an ad hoc
approach relying only on intuition and hands-on experience when designing feedback
control systems. Our approach is to present a control engineering methodology
that, while based on mathematical fundamentals, stresses physical system modeling
.and practical control system designs with realistic system specifications
We believe that the most important and productive approach to learning is for
.each of us to rediscover and re-create anew the answers and methods of the past
Thus, the ideal is to present the student with a series of problems and questions and
point to some of the answers that have been obtained over the past decades.The
traditional method—to confront the student not with the problem but with the finished
solution—is to deprive the student of all excitement, to shut off the creative
impulse, to reduce the adventure of humankind to a dusty heap of theorems. The
issue, then, is to present some of the unanswered and important problems that we
continue to confront, for it may be asserted that what we have truly learned and
.understood, we discovered ourselves
The purpose of this book is to present the structure of feedback control theory
and to provide a sequence of exciting discoveries as we proceed through the text
and problems. If this book is able to assist the student in discovering feedback control
.system theory and practice, it will have succeeded
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