Integration of batch plant scheduling and control by means of hybrid net condition/event system model

The effective operation of a batch processing based plant requires better integration of process engineering functions of the plant, especially scheduling and control functions. In this paper, we try to propose such a method by means of hybrid net condition/event system model. Recently, the authors (1998) proposed hybrid net condition/event system model (HNCES) to describe hybrid systems including batch plants. Unlike hybrid Petri nets, the HNCESs allow one to model a system in a modular manner. We start with the unit level equipment flowsheet for a batch plant. A unit level HNCES model is first derived by identifying the units, the connectivity between each pair of units and by ignoring material transfer equipment. The basic HNCES is then refined to a control-level HNCES model and reduced it to a schedule-level HNCES model of the plant respectively. Model consistency is assured during the refinement and the reduction.