scholarly journals Analysis of Flexible Manufacturing System using Petri Nets to design a Deadlock Prevention Policy

Author(s):  
Shashank Satish More ◽  
Dr. S. G. Bhatwadekar ◽  
1990 ◽  
Vol 23 (8) ◽  
pp. 47-52 ◽  
Author(s):  
Meng Chu Zhou ◽  
F. DiCesare ◽  
D. Rudolph

2014 ◽  
Vol 31 (2) ◽  
pp. 331-352 ◽  
Author(s):  
YiFan Hou ◽  
ZhiWu Li ◽  
Mi Zhao ◽  
Ding Liu

Purpose – Siphon-based deadlock control in a flexible manufacturing system (FMS) suffers from the problems of computational and structural complexity since the number of siphons grows exponentially with respect to the size of its Petri net model. In order to reduce structural complexity of a supervisor, a set of elementary siphons derived from all strict minimal siphons (SMS) is explicitly controlled. The purpose of this paper is through fully investigating the structure of a class of generalized Petri nets, WS3PR, to compute all SMS and a compact set of elementary siphons. Design/methodology/approach – Based on graph theory, the concepts of initial resource weighted digraphs and restricted subgraphs are proposed. Moreover, the concept of augmented siphons is proposed to extend the application of elementary siphons theory for WS3PR. Consequently, the set of elementary siphons obtained by the proposed method is more compact and well suits for WS3PR. Findings – In order to demonstrate the proposed method, an FMS example is presented. All SMS and elementary siphons can be derived from initial resource weighted digraphs. Compared with those obtained by the method in Li and Zhou, the presented method is more effective to design a structural simple liveness-enforcing supervisor for WS3PR. Originality/value – This work presents an effective method of computing SMS and elementary siphons for WS3PR. Monitors are added for the elementary siphons only, and the controllability of every dependent siphon is ensured by properly supervising its elementary ones. A same set of elementary siphons can be admitted by different WS3PR with isomorphic structures.


2014 ◽  
Vol 984-985 ◽  
pp. 111-117 ◽  
Author(s):  
T.R. Chinnusamy ◽  
T. Karthikeyan ◽  
M. Krishnan ◽  
A. Murugesan

A Flexible Manufacturing System (FMS) is an integrated, computer-controlled system of machines, automated handling systems, and storage systems that can be used to simultaneously manufacture a variety of jobs. FMSs can be characterized as asynchronous, concurrent, distributed and parallel systems in which multiple operations share multiple resources so that the performance criteria are optimized. Petri nets (PNs) have recently become a promising approach for modeling FMSs. PNs are formal graphical modeling tool that can be efficiently utilized as a process analysis and modeling tool, because it shows graphically and dynamically to simulate a process in an integrated manner. It is a mathematical modeling technique that is useful for modeling concurrent, asynchronous, distributed, parallel, nondeterministic, and stochastic systems. Unreasonably the dispatching resources/jobs to machine in FMS may result in a deadlock situation and the situation is studied thoroughly and avoided through PN techniques. From the design and analysis point of view, the uses of nets have many advantages in modeling, performance evaluation, qualitative analysis and code generation. Scheduling a manufacturing system is usually a Non-Polynomial hard problem. This means that only heuristic algorithms can be used to provide near-optimal schedule when it is merged with PN. The merging of PNs with knowledge based heuristic techniques seems to be very promising to deal with large complex discrete event dynamic systems. This paper presents a comprehensive survey of FMS that combines PNs with other methods.


Author(s):  
Meng Qin

Many deadlock prevention policies on the basis of Petri nets dealing with deadlock problems in flexible manufacturing systems exist. However, most of them do not consider uncontrollable and unobservable transitions. This chapter solves deadlock problems in Petri nets with uncontrollable and unobservable transitions. A sufficient condition is developed to decide whether an existing deadlock prevention policy is still applicable in a Petri net with uncontrollable and unobservable transitions, when the policy itself is developed under the assumption that all the transitions are controllable and observable. Moreover, the author develops a deadlock prevention policy to design liveness-enforcing supervisors for a class of Petri nets with partial observability and controllability of transitions. Furthermore, a sufficient condition to decide the existence of a monitor to enforce a liveness constraint is developed.


Author(s):  
Jiliang Luo

An algorithm is proposed to equivalently transform original linear constraints on Petri nets, where the uncontrollable subnets are forward-concurrent free nets, into admissible ones. Consequently, this algorithm can be used to design both efficient and optimal supervisors for enforcing linear constraints on Petri nets since the problem on how to enforce admissible constraints has been well solved. Further, the supervisor synthesis procedure is presented using this algorithm. Lastly, it is illustrated by an example where an optimal supervisor is designed for a flexible manufacturing system.


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