A computer system for automation has to satisfy many requirements that we take more or less for granted. It has to run around the clock since a production break may cost enormous amounts of money. It has to work in real time taking various time requirements and process disturbances into consideration. Whatever happens, the system has to behave in a predictable way. It has to be safe, both for the process and for humans.
In most automation systems there are events that will bring the process into another state of operation. Furthermore, there are a lot of applications in both the process and manufacturing industries where control involves primarily switching and sequencing. In both the process and manufacturing industries there is a wealth of applications of switching circuits for combinatorial and sequencing control.
Switching theory, which provides the foundation for binary control, is not only used in automation technology but is also of fundamental importance in many other fields. This theory provides the very principle on which the function of digital computers is based. In general, binary combinatorial and sequencing control is simpler than conventional feedback (analog and digital) control, because both the measurement values and the control signals are binary. However, binary control also has specific properties that have to be considered in more detail.
Keywords
Logical Circuit Boolean Expression Programmable Logic Controller International Electrotechnical Commission Ladder DiagramPreview
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