VHS Case Study 5: Timed Petri net model of steel plant at SIDMAR

This report describes a rather complete timed Petri net model for the steel plant of case study 5. For the description of the semantics used in this model, and for details on the notation, the reader is referred to the report of the [1]. The timed Petri net model of the steel plant is so large that a modularly and hierarchically decomposed net is a more appropriate representation of the model than one single Petri net. We represent all possible execution sequences of the events in the plant as the sequences of events generated by the concurrent execution of two timed Petri net components, and of a schedule (not described in detail here). One component represents the overhead cranes used for moving steel ladles from one treatment station or position to another treatment station or position. The second component of the timed Petri net model represents the material flow, and some of the constraints which can easily be incorporated in the material flow model. It is so large that it is decomposed into several subnets, which have common transitions. These common transitions are exit transitions for one subnet, and entrance transitions for another subnet. All these transitions that appear in two subnets have been explicitly named in the figures to allow unambiguous interpretation of the figures. A first subnet represents the conversion of pig iron into steel and the choice of a recipe. Next there are as many subnets as there are recipes, each subnet representing the sequence of treatments as specified by that recipe. To fix the notation we say there ar