Article,
Deadlock Control Based on Capacity Restrictions for FMS
IMA Journal of Mathematical Control and Information, (Jul 27, 2016)
DOI: 10.1093/imamci/dnw037
Abstract
In flexible manufacturing systems (FMS), deadlock prevention is an important problem to be solved. Petri nets are a powerful tool and wildly used to model and control FMS. Based on the capacity restrictions for activity places in the Petri net model of an FMS, a new approach is presented to implement the liveness of the controlled net system in this research. First, given a Petri net prone to deadlocks, its initial capacity vector is decided. Then, an algorithm is proposed to compute its final capacity vector iteratively. At each iteration, the capacity of one activity place is decreased by one. The objective is to prevent the excessive occupancy of one resource by one production process, which is an important reason causing a deadlock. This process is carried out until the net model becomes live. With the constraints by the final capacity vector, the controlled net is live. It is proved the iterative algorithm is convergent. Considering the redundancy of capacity restrictions, another algorithm is given to eliminate it. The presented method for FMS control guarantees its live operation and high performance in terms of resource utilization. Generally, the proposed method is applicable, easy to use, effective and straightforward. Finally, two parameterized examples are used to demonstrate the applicability and effectiveness of the proposed approach.
