scholarly journals Liveness characteristic analysis of a class of Petri nets

2018 ◽  
Vol 10 (6) ◽  
pp. 168781401878148
Author(s):  
Miao Liu ◽  
Zhou He
Keyword(s):  
Computational Complexity ◽  
Petri Nets ◽  
Flexible Manufacturing ◽  
Flexible Manufacturing Systems ◽  
Manufacturing Systems ◽  
Effective Algorithm ◽  
Finite Capacity ◽  
Characteristic Analysis ◽  
Control Actions ◽  
Sequential Processes

Petri nets are an effective tool for analyzing and modeling the dynamic behavior of flexible manufacturing systems. Finite capacity systems of simple sequential processes with resources are an important subclass of Petri nets, for which this article gives a liveness characteristic analysis. First, an effective algorithm for deciding the liveness of finite capacity systems of simple sequential processes with resources is developed by analyzing the relation between the structural properties of resource subnets and the strict minimal siphons. Then, a liveness condition of finite capacity systems of simple sequential processes with resources is accordingly established. Based on the proposed liveness condition, an algorithm for configuring an initial marking for a finite capacity systems of simple sequential processes with resources is given, and therefore, a live finite capacity systems of simple sequential processes with resources net with a configured initial marking can be obtained, which avoids the siphon enumerations and the addition of any control actions. It is shown that the computational complexity of both the developed liveness deciding and the initial marking configuration algorithms is polynomial. Examples are finally provided to illustrate the mentioned results.

scholarly journals Global Supervisory Structure for Decentralized Systems of Flexible Manufacturing Systems Using Petri Nets

Processes ◽  
2019 ◽  
Vol 7 (9) ◽  
pp. 595 ◽  
Author(s):  
Muhammad Bashir ◽  
Liang Hong
Keyword(s):  
Computational Complexity ◽  
Petri Nets ◽  
Petri Net ◽  
Flexible Manufacturing ◽  
Flexible Manufacturing Systems ◽  
Manufacturing Systems ◽  
Structural Complexity ◽  
Decentralized Systems ◽  
The Cost ◽  
Global Controller

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.

scholarly journals One Novel and Optimal Deadlock Recovery Policy for Flexible Manufacturing Systems Using Iterative Control Transitions Strategy

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Ter-Chan Row ◽  
Wei-Ming Syu ◽  
Yen-Liang Pan ◽  
Ching-Cheng Wang
Keyword(s):  
Petri Nets ◽  
Petri Net ◽  
Flexible Manufacturing ◽  
Flexible Manufacturing Systems ◽  
Manufacturing Systems ◽  
Experimental Results ◽  
Reachability Graph ◽  
Sequential Processes ◽  
Iterative Control

This paper focuses on solving deadlock problems of flexible manufacturing systems (FMS) based on Petri nets theory. Precisely, one novel control transition technology is developed to solve FMS deadlock problem. This new proposed technology can not only identify the maximal saturated tokens of idle places in Petri net model (PNM) but also further reserve all original reachable markings whatever they are legal or illegal ones. In other words, once the saturated number of tokens in idle places is identified, the maximal markings of system reachability graph can then be checked. Two classical S3PR (the Systems of Simple Sequential Processes with Resources) examples are used to illustrate the proposed technology. Experimental results indicate that the proposed algorithm of control transition technology seems to be the best one among all existing algorithms.

Optimal enforcement of liveness for decentralized systems of flexible manufacturing systems using Petri nets

2020 ◽  
Vol 42 (12) ◽  
pp. 2206-2220
Author(s):  
Muhammad Bashir
Keyword(s):  
Computational Complexity ◽  
Petri Nets ◽  
Petri Net ◽  
Supervisory Control ◽  
Flexible Manufacturing ◽  
Flexible Manufacturing Systems ◽  
Manufacturing Systems ◽  
Common Elements ◽  
Decentralized Controllers ◽  
The Given

The decentralized supervisory structure has drawn much attention in recent years. Many studies are reported in the paradigm of automata while few can be found in the Petri net model. This paper proposes a new method for decentralized supervisory control using the Petri net paradigm. Two efficient Algorithms are developed in the proposed method. Algorithm 1 is used to compute decentralized working zones from the given LS3PR Petri net model for flexible manufacturing systems. Algorithm 2 is used to compute the decentralized controllers that enforced liveness to the decentralized working zones. The sequential assembling is used to reconnect and controlled the working zones via decentralized controllers. The decentralized controller is added to the decentralized working zones that have common elements, that is, common transitions. The proposed method has the following advantages: (i) it can be applied to a complex Petri net model for flexible manufacturing systems, (ii) the proposed methods has less computational complexity when compared with the previous methods, (iii) the proposed method can obtain a minimal number of decentralized controllers that enforce liveness of the uncontrolled Petri net model. Experimental examples are presented to explore the applicability of the proposed methods.

A Method to Compute Siphons Based on Matrix Manipulation

2011 ◽  
Vol 88-89 ◽  
pp. 486-490
Author(s):  
Xue Peng Chen ◽  
Liang Xu Zhao ◽  
Shan Fa Lin ◽  
Wen Hui Wu
Keyword(s):  
Petri Nets ◽  
Petri Net ◽  
Flexible Manufacturing ◽  
Flexible Manufacturing Systems ◽  
Manufacturing Systems ◽  
Incidence Matrix ◽  
Sequential Processes ◽  
Matrix Manipulation ◽  
Structural Object ◽  
And Control

As a structural object of Petri nets, siphons are significant in the analysis and control of deadlocks in a Petri net. However, some existing siphon computation methods are quite time-consuming. In this paper, based on incidence matrix manipulation, a new method is proposed to compute a set of siphons in a class of Petri nets called systems of simple sequential processes with resources (S3PR). The proposed method consists of two algorithms: 1) computation of an unmarked maximal siphon and 2) obtain minimal siphons from an unmarked maximal siphon. A flexible manufacturing systems (FMS) example is used to illustrate the proposed method.

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