MODELING OF COMBINED DISCRETE-CONTINUOUS PROCESSES

The dynamic behavior of processing systems exhibits both continuous an d significant discrete aspects. Process simulation is therefore a comb ined discrete/continuous simulation problem. In addition, there is a c ritical need for a declarative process modeling environment to encompa ss the entire range of processing system operation, from purely contin uous to batch. These issues are addressed by this article. A new forma l mathematical description of the combined discrete/continuous simulat ion problem is introduced to enhance the understanding of the fundamen tal discrete changes required to model processing systems. The modelin g task is decomposed into two distinct activities: modeling fundamenta l physical behavior, and modeling the external actions imposed on this physical system. Both require significant discrete components. Import ant contributions include a powerful representation for discontinuitie s in physical behavior, and the first detailed consideration of how co mplex sequences of control actions may be modeled in a general manner.