Liveness of Disjunctive and Strict Single-Type Automated Manufacturing System: An ROPN Approach

The resource-oriented Petri net (ROPN) modeling method is applied in this paper to model a class of automated manufacturing systems (AMS) named disjunctive and strict single-type AMSs (DS-AMS), where multiple units of a single resource type are required to support a processing stage. This modeling method is more compact and intuitive than the existing ones in the contemporary literature, named weighted systems of simple sequential processes with resources. Based on the ROPN model, a significant result is re-proved in a different way, which is more succinct and understandable. Such a result presents a sufficient and necessary condition on the liveness of an ROPN. Furthermore, based on this result, we develop efficient strategies to ensure the liveness of an ROPN modeling a DS-AMS. To enforce the liveness of such an ROPN, only some specific transitions need to be controlled by taking advantage of its structural properties. Also, an efficient approach is developed to implement the proposed policy by identifying and controlling such transitions. Two examples are employed to demonstrate the efficiency of the developed method. Some limitations of the method are pointed out in the end, which will be studied in the future.