Near-Optimal Distributed Control of Automated Manufacturing Systems With Assembly Operations Using Petri Nets

Assembly operations are common in automated manufacturing systems (AMSs). AMSs with assembly operations belong to complex systems due to their complicated structures. The traditional supervisory control techniques (SCTs) are generally not suitable for such large-scale systems. In this article, we propose a distributed control technique for AMSs with assembly operations to achieve a near-optimal liveness enforcement. Specifically, we define a type of decomposable system modeled by decomposable augmented marked graphs (AMGs) and create buffer-linked AMGs (BAMGs) by connecting each subsystem through buffers with specified capacities. Next, we construct the complemented subsystems to ensure structural completeness and simplify their structures to condense their reachability graphs. By conducting liveness analysis of BAMGs employing siphons, we demonstrate that the liveness of BAMGs depends solely on that of each individual subsystem. Finally, we design monitors for simplified subsystems utilizing reachability analysis and achieve distributed control of AMGs. Since the scale of reachable states is greatly reduced in simplified subsystems compared with the original AMGs, our method can save a significant amount of computation. An experimental study demonstrates the effectiveness of the proposed method.