Introduction to Digital Control

There is a need to control the evolution with time of one or more of the system variables in many engineering systems. Controllers are required to ensure satisfactory transient and steady-state behavior for these engineering systems. To guarantee satisfactory performance in the presence of disturbances and model uncertainty, most controllers in use today employ some form of negative feedback. A sensor is needed to measure the controlled variable and compare its behavior to a reference signal. Control action is based on an error signal defined as the difference between the reference and the actual values. This chapter explains the reasons for the popularity of digital control systems. Following this, it illustrates a block diagram for digital control of a given analog control system. Furthermore, it explains the structure and components of a typical digital control system. Digital control offers distinct advantages over analog control that explain its popularity. The advantages are—accuracy, implementation errors, flexibility, speed, and cost. Finally, the chapter discusses examples of control systems where digital implementation is now the norm.