The use of a microprocessor in the control of a closed loop automatic system

Abstract

Automatic systems have been widely used in industry since their inception, the reason being that they are more reliable, accurate and overall efficient than man controlled systems. The word automatic is generally applied to systems which can operate satisfactorily, to a class of inputs and to a variety of ‘operating conditions without human intervention. Automatic Control systems replace the human factor by means of physical elements, such that the operator is relieved of time consuming and tiresome tasks. In order to replace efficiently the human factor in a control system, equipment must’ be devised to perform all those functions normally carried out by man. There are two main categories of control systems, open loop systems and closed loop systems. An open loop. system is one which has no means of varying system output except when in accordance with the inherent characteristic of the system. Such a system does not necessarily reach its goal (especially if changes in operating conditions occur) without human intervention. The human operator acts as a feedback link, he compares the output variable to that required and varies the input to the controller accordingly. In this way the open loop system is converted to a closed loop system. A closed loop system is one which has one or more feedback paths. If the required feedback function in the feedback loop of a closed loop system is achieved by means of physical systems other than man, then the resulting system will be an automatic closed loop control system. [...]