The use of self-tuning to resolve the problem of uncertain dynamics is the theme of this book. The idea behind self-tuning is to adjust the controller settings automatically, based on the measured input/output behaviour of the real plant. Microprocessors have played a crucial role in achieving acceptance of self-tuning for they allow the computationally demanding algorithms to be implemented cheaply. Self-tuners do not remove the need for an engineer's skill but allow him to think more positively about the real control needs and constraints of his plant rather than simply hoping that manually-tuned and fixed PID laws will solve all his problems.