Abstract
Decentralized supervisory structure has drawn much attention in recent years to address the computational complexity in designing supervisory structures for large Petri net model. Many studies are reported in the paradigm of automata while few can be found in the Petri net paradigm. The decentralized supervisory structure can address the computational complexity, but it adds the structural complexity of supervisory structure. This paper proposed a new method of designing a global controller for decentralized systems of a large Petri net model for flexible manufacturing systems. The proposed method can both reduce the computational complexity by decomposition of large Petri net models into several subnets and structural complexity by designing a global supervisory structure that can greatly reduce the cost at the implementation stage. Two efficient algorithms are developed in the proposed method. Algorithm 1 is used to compute decentralized working zones from the given Petri net model for flexible manufacturing systems. Algorithm 2 is used to compute the global controller that enforces the liveness to the decentralized working zones. The ring assembling method is used to reconnect and controlled the working zones via a global controller. The proposed method can be applied to large Petri nets size and, in general, it has less computational and structural complexity. Experimental examples are presented to explore the applicability of the proposed method.
Highlights
Due to the complexity of flexible manufacturing systems in the recent years, decentralized systems control has drawn much attention worldwide by the researchers in the area of the discrete event systems
This paper focuses on the design of a global supervisory structure for decentralized systems using the Petri nets paradigm
We proposed a new method to design a global supervisory structure of the decentralized systems using Petri nets for flexible manufacturing systems
Summary
Due to the complexity of flexible manufacturing systems in the recent years, decentralized systems control has drawn much attention worldwide by the researchers in the area of the discrete event systems. Large-scale discrete event systems (DES) are modeled through the composition of many smaller subsystems representing shared resources by the concurrent operations. The controlled of large-size flexible manufacturing systems is tedious and time-consuming, perhaps it required huge memory space due to a large number of its state space. To reduce the computational complexity and required memory space for the analysis and control of large flexible manufacturing systems, we decomposed the systems into several working zones (i.e., several sub-problems). Several methods are developed in the literature to analyze the decentralized systems of DES-based on the system applications. The DES find application in the areas of automation [1,2], software development [3], computer engineering [4,5], communication
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