Modeling and Performance Analysis of a Flexible PCB Assembly Station Using Petri Nets

This paper presents Petri net modeling and performance analysis of a flexible workstation for automatic assembly of printed circuit boards. Concentrating on the operational aspects, we construct ordinary and temporal Petri net models for an existing flexible workstation (AT&T FWS-200). These models enable designers to have better understanding of concurrency, synchronization, mutual exclusion, and sequential relations involved in the system control from the graphical representations of Petri nets. From the models the performance analysis of system operations under different settings can be conducted, with the results used to help designers choose the best operational setting based on system parameters such as component insertion time and robot failure rate. We focus our performance analysis on two cases: one is the Petri net with parallel mutual exclusion based control structure, and the other is the control structure based on the marked graph. The analysis results lead to the conclusion that the former structure has better performance in terms of throughput and equipment utilization. The approaches as presented in this paper can be generalized and applied to many other applications of multi-robot assembly systems.