The presence of considerable time delays in many industrial processes is
well recognized and achievable performances of conventional unity
feedback control systems are degraded if a process has a relatively
large time delay compared to its time constants. In this case, dead time
compensation is necessary in order to enhance the performances. The most
popular scheme for such compensation is the Smith Predictor, but it is
unsuitable for unstable or lightly damped processes because the
compensated closed-loop system always contains the process poles
themselves. An alternative scheme for delay elimination from the
closed-loop is the finite spectrum assignment (FSA) strategy and it can
arbitrarily assign the closed-loop spectrum. One may note that the
Smith- Predictor Control can be found in delay systems control books and
many process control books, but the FSA control is rarely included in
these books. It is therefore timely and desirable to fill this gap by
writing a book which gives a comprehensive treatment of the FSA
approach. This is useful and worthwhile since the FSA provides not only
an alternative way but also certain advantages over the Smith-Predictor.
The book presents the state-of-the-art of the finite spectrum assignment
for time-delay systems in frequency domain. It mainly contains those
works carried out recently by the authors in this field. Most of them
have been published and others are awaiting publication. They are
assembled together and reorganized in such a way that the presentation
is logical, smooth and systematic.
