Digital Control Systems

Abstract

A control system consists of two main parts. One is the object being controlled, often referred to as the plant, and the other is the controller. With the plant, it is possible to identify certain outputs, which are variables to be controlled and certain control inputs, which are variables to be manipulated, so as to achieve the desired control action. A system where either the input or output signal is digital is referred to as a digital system, and a control system where the controller is a digital system is referred to as a digital control system. The first step in the analysis and design of digital control systems is the mathematical modeling of the analog system being controlled. The two most common models are transfer-function models and state-variable models. The next step is to configure the analog-to-digital (A/D) and digital-to-analog subsystems (D/A), to interface the controlled system with the digital controller. Finally, suitable performance measures must be specified and a design algorithm developed. With the increase in computing power it can be expected that digital control theory will be developed for the design of increasingly complex systems. The chapter observes that future developments in digital control theory can be expected to be more intimately related to the theory and operation of computers and computer networks.