Manufacturing modeling using process nets with resources

Presents a class of Petri nets called process nets with resources (PNRs) for modeling manufacturing systems where only parts can interact with resources, and resources alone cannot interact with one another. PNRs properly includes S³PR, augmented marked graphs, and, sub-classes of RCN merged nets and ERCN merged nets where firing a transition may only generate parallel processes for parts but not for resources. As a result, PNRs can model far more complex manufacturing process flows and resource sharing than these nets. To construct a PNR, we first build a process net to specify the process flow for each part type. A process net is a consistent, conservative, strongly-connected, and live Petri net and satisfies three conditions. Then resource places denoting the availability of resource types are added to the process nets such that for each resource place, the input and output transitions of the resource place generate a transition sub-net. For qualitative analysis, we show that reversibility of a PNR is assured if and only if there exists no unmarked siphon. Liveness of a PNR can be verified by checking the potential firability of each isolated process net, which is a process net with all resources allocated to it. For certain sub-classes of process nets, conditions for potential liveness are obtained