Modeling buffers in automated manufacturing systems using Petri nets

Petri net design approaches for automated manufacturing systems are discussed, with emphasis on modular design methods for buffers. The simple Petri net module for a buffer is extended to a module for a generalized buffer which can be shared and which can accommodate a number of distinct types of parts. Theoretical results about the preservation of system properties such as boundedness, liveness, and reversibility are presented for when a Petri net contains such buffer modules. Two theorems provide certain conditions to achieve such property preservation. Safe Petri net modules for a buffer are designed using safe places only. The results are illustrated by two manufacturing examples: a multiple-machine and multiple-buffer production line, and an automatic storage-retrieval system in a flexible manufacturing system.