Petri net

About: Petri net is a research topic. Over the lifetime, 25039 publications have been published within this topic receiving 406994 citations.

Computationally Improved Optimal Deadlock Control Policy for Flexible Manufacturing Systems

Abstract: Deadlock prevention, deadlock detection, and deadlock avoidance strategies are used to solve the deadlock problems of flexible manufacturing systems. The theory of regions is recognized as the unique method for obtaining maximally permissive (i.e., optimal) controllers in the existing literature. All legal and live maximal behavior of a Petri net model can be preserved by using a marking/transition-separation instance (MTSI). However, obtaining them is an extremely time consuming problem. This work proposes crucial MTSIs that allow designers to employ much fewer MTSIs to deal with deadlocks. The advantage of the proposed policy is that an optimal deadlock controller can be obtained with drastically reduced computation. Experimental results, by varying the markings of given net structures, indicate that it is the most efficient policy to obtain such controllers.

Observer-based state-feedback control of timed Petri nets with deadlock recovery

Abstract: This paper discusses the problem of controlling a timed Petri net whose marking cannot be measured but is estimated using an observer. The control objective is that of enforcing a set of generalized mutual exclusion constraints (GMEC) and all transitions are assumed to be controllable. We show that the use of marking estimates may significantly reduce the performance of the closed-loop system and in particular may lead to a deadlock. First, we present a linear algebraic characterization of deadlock markings based on siphon analysis. Second, we show how this characterization may be used to derive a procedure that may be invoked to recover from a controller induced deadlock. Finally, we assume that the timing delays associated to transitions are known and show how this knowledge can be used to improve the marking estimate and to recover the net from partial deadlocks. This procedure is similar to the one used for deadlock recovery and may be invoked whenever a transition has not fired for a time longer than its expected delay.

Repairable fault tree for the automatic evaluation of repair policies

Abstract: Fault trees are a well known mean for the evaluation of dependability of complex systems. Many extensions have been proposed to the original formalism in order to enhance the advantages of fault tree analysis for the design and assessment of systems. In this paper we propose an extension, repairable fault trees, which allows the designer to evaluate the effects of different repair policies on a repairable system: this extended formalism has been integrated in a multi-formalism multi-solution framework, and it is supported by a solution technique which transparently exploits generalized stochastic Petri nets (GSPN)for modelling the repairing process. The modelling technique and the solution process are illustrated through an example.

Cross-organizational collaborative workflow mining from a multi-source log

Abstract: Today's enterprise business processes become increasingly complex given that they are often executed by geographically dispersed partners or different organizations. Designing and modeling such a cross-organizational workflow is a complicated, time-consuming process and requires that a designer has extensive experience. Workflow logs captured by different cross-organizational systems provide a very valuable source of information on how business processes are executed in reality and thus can be used to derive workflow models through process mining. In this paper, we investigate the application of process mining for workflow integration based on the concept of RM_WF_Net, a type of Petri net extended with resource and message factors. Four coordination patterns are defined for workflow integration. A process mining approach is presented to discover the coordination patterns between different organizations and the workflow models in different organizations from the running logs containing the information about resource allocation. A process integration approach is then presented to obtain the model for a cross-organizational workflow based on the model mined for each organization and the coordination patterns between different organizations.