2 Computer-Aided Control Systems Design
stability using the frequency domain approach. This was later extended [5] during
the next decade to give rise to one of the most widely applied control system design
methodologies [6]. Based on the Root Locus method [2,7], afew designed techniques
that allowed the roots of the characteristics equation to be displayed in a graphical
form were subsequently proposed.
The invention of computers in the 1950s gave rise to the application of state-space
equations that use vector matrix notation for machine computation. The concept
of optimum [8] design was rst proposed. The method of performing dynamic
programming [9] was then developed at the same time as the maximum principle[10].
At the initial conference of the International Federation of Automatic Control, the
concept of observability and controllability [11] was introduced. Around the same
period, Kalman demonstrated that when the system dynamic equations are linear,
performance criterion is quadratic and can be controlled using the LQ method. With
the concept of the Kalman lter [12], which combined with an optimal controller,
alinear-quadratic-Gaussian (LQG) control was introduced.
The 1980s showed great advances in control theory for the robust design of
systems with uncertainties in their dynamic equations. The works on H-innity norm
and μ-synthesis theory [13–15] demonstrated how uncertainty can be modeled in the
system equations. A decade later, the concept of intelligent control systems was devel-
oped. An intelligent machine [16] that is able to give a better behavior under uncer-
tainty condition was introduced. Intelligent control theory has the ideas laid down in
the area of Articial Intelligence (AI). Articial Neural Networks [17–19] uses many
simple elements operating in parallel to emulate how their biological counterparts are
used. Subsequently, the idea of fuzzy logic [20] was developed to allow computers
to model human vagueness. The fuzzy logic [21–24] controllers offer some form of
robust control without the requirement to model the system dynamic behavior.
Thus, control theories have made signicant strides in the past 100 years in
history. New mathematical techniques made it possible to more accurately control
signicantly more complex dynamical systems than the original yball governor.
These techniques include developments in optimal control in the 1950s and 1960s,
followed by progress in stochastic, robust, adaptive, and optimal control methods in
the 1970s and 1980s, and intelligent control in 1990s. Applications of control meth-
odology have helped to make efcient power generation, space travel, communication
satellites, aircraft, and underwater exploration possible.
1.2 COMPUTER-AIDED CONTROL SYSTEM DESIGN
One of the aspects of control systems that has received considerable attention is that of
developing efcient and stable computational algorithms. Parallel with the advances
in modern control, computer technology has made its own progress and has played
a vital role in implementing the control algorithms. As a result, the eld of control
has been inuenced by the revolution in computer technology. Now, most control
engineers have easy access to a powerful computer package for system analysis and
design. In fact, computers have become an integral part of control systems. With
the progress in computing ability, the classes of problems which can be modeled,
analyzed, and controlled are considerably larger than those previously treated.