Batch process modelling using Petri nets

The automation of batch processes poses difficult issues mainly because it is necessary to concurrently operate with continuous and discrete models. In this paper, we analyse how the hierarchical approach used in the field of discrete manufacturing systems can be extended to batch systems. This hierarchical approach gave rise to three levels which are composed by a discrete event model modelling the control policy (discrete view of the process) and by a continuous model of the process (continuous view of the process). The consistency between the continuous models of the process and the physical state of the plant is ensured by an event generator. This event generator is presented and various cases of variables are considered. Finally, a discrete event modelling of the control policies is illustrated through an example of a batch multipurpose plant, using Petri nets