Introduction

Abstract

Prior to the 1940s, most industrial systems were run essentially manually or using on-off control. Many operators were needed to keep watch on the many variables in the plant. With the continuous industrialization over the last several decades, manufacturing and production have taken off at an incredibly high speed in almost every part of the world. As a consequence of the expanding scale and volume of production, there could be hundreds or even thousands of variables to be controlled in a plant. The manual effort thus needed in operation is tremendous. With increasing labor and equipment costs, and with eager demand for high precision, quality and efficiency, the idea of employing operators for the control of physical systems rapidly became uneconomical and infeasible. Automatic control thus becomes a solution much sought after. The fundamental component in an automatic control system is the so called “controller”. It could either be a piece of hardware or software code in a computer. Its job is to receive information about the system from a variety of sensors, process it, and automatically generate commands for corrective action to bring the variable of interest to its desired value or trajectory. Wide applications of automatic control have driven great attention to its theoretical development. Since the age of the familiar classical control theory, many new and sophisticated theories have evolved and striking developments have taken place especially since 1950s.