Computer Control: An Overview

Computers are today essential for implementing controllers in many different situations. The computers are often used in embedded systems. An embedded system is a built-in computer/microprocessor that is a part of a larger system. Many of these computers implement control functions of different physical processes, for example, vehicles, home electronics, cellular telephones, and standalone controllers. The computers are often hidden for the end-user, but it is essential that the whole system is designed in an effective way. Using computers has many advantages. Many problems with analog implementation can be avoided by using a computer, for instance, there are no problems with the accuracy or drift of the components. The computations are performed identically day after day. It is also possible to make much more complicated computations, such as iterations and solution of system of equations, using a computer. All nonlinear, and also many linear operations, using analogue technique are subject to errors, while they are much more accurately made using a computer. Logic for alarms, start-up, and shut-down is easy to include in a computer. Finally, it is possible to construct good graphical user interfaces. However, sometimes the full advantages of the computers are not utilized. One reason for this is when the computer is only used to approximately implement an analog controller. The full potential of a computer-controlled system is only obtained when also the design process is regarded from a sampled-data point of view. This paper gives a brief review of some of the tools that are important for understanding, analyzing, designing, and implementing sampled-data control systems.