Architectures for automated flexible manufacturing cells with routing flexibility
Ali Yalçin, Thomas O. Boucher · 2000
This research addresses the modeling and real-time control of automated flexible manufacturing cells with routing flexibility and direct address material handling. Two architectures are proposed to model these systems; one is based on Finite Automata and one is based on Colored Petri Nets. For the architecture based on Finite Automata, a maximally permissive deadlock avoidance policy that incorporates routing flexibility into operational control of the cell is proposed. The deadlock avoidance policy is implemented using three different algorithms and advantages and disadvantages as well as state space increase of each implementation is discussed. An efficient algorithm to detect partial deadlocks is proposed and shown to be effective in decreasing the search space for the proposed deadlock avoidance policy. Experiments indicate that incorporating routing flexibility into operational control of the cell increases overall resource utilization and improves system performance. The proposed control policy is shown to be applicable to a broader range of systems and allows for better performance in the system than other control policies in the literature that incorporate dynamic routing flexibility. The architecture based on Colored Petri Nets (CPN) captures both alternate machining and alternate sequencing options in the system, extending the modeling power of the previous CPN based methodologies. The decision of which alternative route to take is postponed until the time at which the resource allocation decision is made, which allows for dynamic flexible routing. The architecture also separates the operation to be performed on the part from the machine that processes it. In this manner routing plans are generated automatically whereas, in the architecture based on Finite Automata, routing plans must be explicitly defined. Using t-invariants and current marking of the net, detection of partial deadlocks within Petri Net formalism is also described.