1 - Introduction to linear feedback controls

Abstract

Automation and controls date back thousands of years and likely begun with the desire to keep water levels for irrigation constant. Much later, the industrial revolution brought a need for methods and systems to regulate machinery, for example, the speed of a steam engine. Since about two centuries ago, engineers have found methods to describe control systems mathematically, with the result that the system behavior could be more accurately predicted and control systems more accurately designed. Feedback controls are control systems where a sensor monitors the property of the system to be controlled, such as motor speed, pressure, position, voltage, or temperature. Common to all feedback control systems is the comparison of the sensor signal to a reference signal and the existence of a controller that influences the system to minimize the deviation between the sensor and reference signals. Feedback control systems are designed to meet specific goals, such as keeping a temperature or speed constant, or to accurately follow the reference signal. In this chapter, some of the fundamental principles of feedback control systems are introduced, and some common terms defined.