Deadlock-free control of ratio-enforced automated manufacturing systems with flexible routes and assembly operations

In the context of automated manufacturing systems (AMS), Petri nets are widely adopted to solve the modeling, analysis, and control problems. So far, nearly all well-known Petri net approaches study AMS with either flexible routes or assembly operations, whereas few work investigates their combination. In this paper, we propose a novel class of nets, which can well deal with both features. We also derive a supervisory controller for on-line ratio enforcement among all processes. Using structural analysis, we show that liveness of such systems can be attributed to the absence of undermarked siphons. We also reveal the design separability between ratio-enforcing and liveness-enforcing supervisors.