Automatic program generation for PC-based sequence control problems

This paper describes a software tool for the automatic generation of ladder diagrams used in sequence control problems with programmable controllers. Input to the system consists of precedence relationships among activities and a functional description of input and output devices. A network representation of sequence control problems is introduced. The status of the control system at different instances of the operational cycle is progressively constructed based on input information. Two methods for the deduction of ladder diagrams using the notions of event and activity states are described. The concepts are illustrated with an example.