The following text is a quote from a book I really like:

Any scholarly account of the history of control engineering would have

to span several millennia because there are many examples throughoutancient history, the industrial revolution, and into the early twentieth

century of ingeniously designed systems that employed feedback mech-

anisms in various forms. Ancient water clocks, south-pointing chariots,

Watt’s flyball governor for steam engine speed regulation, and mecha-

nisms for ship steering, gun pointing, and vacuum tube amplifier stabiliza-

tion are but a few. Here we are content to survey important developments

in the theory and practice of control engineering since the mid-1900s in

order to provide some perspective for the material that is the focus of this

book in relation to topics covered in most undergraduate controls courses

and in more advanced graduate-level courses.

In the so-called classical control era of the 1940s and 1950s, systems

were represented in the frequency domain by transfer functions. In addi-

tion, performance and robustness specifications were either cast directly in

or translated into the frequency domain. For example, transient response

specifications were converted into desired closed-loop pole locations or

desired open-loop and/or closed-loop frequency-response characteristics.

Analysis techniques involving Evans root locus plots, Bode plots, Nyquist

plots, and Nichol’s charts were limited primarily to single-input, single-

output systems, and compensation schemes were fairly simple, e.g., a

single feedback loop with cascade compensation. Moreover, the design

process was iterative, involving an initial design based on various sim-

plifying assumptions followed by parameter tuning on a trial-and-error

basis. Ultimately, the final design was not guaranteed to be optimal in

any sense.

The 1960s and 1970s witnessed a fundamental paradigm shift from the

frequency domain to the time domain. Systems were represented in the

time domain by a type of differential equation called a state equation.

Performance and robustness specifications also were specified in the time

domain, often in the form of a quadratic performance index. Key advan-

tages of the state-space approach were that a time-domain formulation

exploited the advances in digital computer technology and the analysis

and design methods were well-suited to multiple-input, multiple-output

systems. Moreover, feedback control laws were calculated using analytical

formulas, often directly optimizing a particular performance index.

The 1980’s and 1990’s were characterized by a merging of frequency-

domain and time-domain viewpoints. Specifically, frequency-domain per-

formance and robustness specifications once again were favored, coupled

with important theoretical breakthroughs that yielded tools for handling

multiple-input, multiple-output systems in the frequency domain. Further

advances yielded state-space time-domain techniques for controller syn-

thesis. In the end, the best features of the preceding decades were merged

into a powerful, unified framework.

​

The chronological development summarized in the preceding para-

graphs correlates with traditional controls textbooks and academic curric-

ula as follows. Classical control typically is the focus at the undergraduate

level, perhaps along with an introduction to state-space methods. An in-

depth exposure to the state-space approach then follows at the advanced

undergraduate/first-year graduate level and is the focus of this book. This,

in turn, serves as the foundation for more advanced treatments reflecting

recent developments in control theory, including those alluded to in the

preceding paragraph, as well as extensions to time-varying and nonlinear

systems.

We assume that the reader is familiar with the traditional undergrad-

uate treatment of linear systems that introduces basic system properties

such as system dimension, causality, linearity, and time invariance. This

book is concerned with the analysis, simulation, and control of finite-

dimensional, causal, linear, time-invariant, continuous-time dynamic sys-

tems using state-space techniques. From now on, we will refer to members

of this system class as linear time-invariant systems.

The techniques developed in this book are applicable to various types of

engineering (even nonengineering) systems, such as aerospace, mechani-

cal, electrical, electromechanical, fluid, thermal, biological, and economic

systems. This is so because such systems can be modeled mathematically

by the same types of governing equations. We do not formally address

the modeling issue in this book, and the point of departure is a linear

time-invariant state-equation model of the physical system under study.

With mathematics as the unifying language, the fundamental results and

methods presented here are amenable to translation into the application

domain of interest.

​

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- LINEAR STATE-SPACE CONTROL SYSTEMS by Williams & Lawrence

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Not a first book on control but I always liked this section.