The Development of Complex Data Structures Using Object Enhanced Time Petri Nets

The paper addresses the fault detection problem for discrete event systems modeled by Petri nets (PN). Assuming that the PN structure and initial marking are known, faults are modeled by unobservable transitions. The paper recalls a previously proposed diagnoser that works online and employs an algorithm based on the definition and solution of some integer linear programming problems to decide whether the system behavior is normal or exhibits some possible faults. To reduce the on-line computational effort, we prove some results showing that if the unobservable subnet enjoys suitable properties, the algorithm solution may be obtained with low computational complexity. We characterize the properties that the PN modeling the system fault behavior has to fulfill and suitably modify the proposed diagnoser.

A set of non-negative integral vectors is said to be right-closed if the presence of a vector in the set implies all term-wise larger vectors also belong to the set. A set of markings is control invariant with respect to a Petri Net (PN) structure if the firing of any uncontrollable transition at any marking in this set results in a new marking that is also in the set. Every right-closed set of markings has a unique supremal control invariant subset, which is the largest subset that is control invariant with respect to the PN structure. This subset is not necessarily right-closed. In this paper, we present an algorithm that computes the supremal right-closed control invariant subset of a right-closed of markings with respect to an arbitrary PN structure. This set plays a critical role in the synthesis of Liveness Enforcing Supervisory Policies (LESPs) for a class of PN structures, and consequently, the proposed algorithm plays a key role in the synthesis of LESPs for this class of PN structures.

The authors propose evolutionary Petri net consisting of units in order to obtain a structural model of team medical care automatically. The number of medical staffs is not sufficient in aged societies, so the work efficiency must be improved. The authors conceive that a Petri net can be used to express cooperative operation; therefore, the structure of a Petri net might assist in understanding the whole team medical care in hospitals and facilities. Evolutionary Petri net is a method to create the best structure of a Petri net that expresses a target workflow well and evolves the genes of individuals correspond to Petri nets. In the previous work, the authors represented each gene as a combination of nodes. However, the representation frequently generated worthless individuals that do not have a Petri net structure. In this work, the authors represent each gene as a combination of units that consist of two types of nodes. Additionally, the authors propose a new method to separately calculate the fitness value on the Petri net structure and that on the unit structures. The authors verified that the total fitness value of the best individual quickly reached the best value by applying genetic operators along with the balance of the two fitness values.

Petri net as a modeling tool

This article addresses expressiveness problems for Petri nets and their useful extension for modeling and control of a system that can be modeled with Petri nets. We construct some Petri net modules, namely, an enabling module, an inhibitor module and a Modulo-N counter, which are useful for system operations. We also present the simplifications for the enabling and inhibitor modules. Then, we propose two new types of arcs, namely, enabling and inhibitor arcs, with a weighted function set. The arcs with the weighted function set from places to transitions are the marked arcs. A function set is employed to denote the weight of an arc according to the system requirements. They are very useful to solve the resource reallocation problem in a resource allocation system, where resource sharing contributes to the occurrences of deadlocks. Finally, two examples are used to show the advantages of the presented new types of arcs.

This paper presents a new scheduling method for a flexible manufacturing system (FMS) in a Petri net framework. Petri nets can concisely model multiple lot sizes for each job, the strict precedence constraint, multiple kinds of resources, and concurrent activities. To decrease the likelihood of rejecting the critical markings, our algorithm adopts an improved checking method for previous generated marking. To reduce the computation complexity, an elaborate scheme is applied, which performs A* search locally and backtracking search globally in the reachability graph of the Petri net. Some numerical experiments are carried out to demonstrate usefulness of the algorithm.

For automated manufacturing systems (AMSs), deadlock resolution in terms of Petri nets remains an attractive topic to which many approaches are dedicated. However, few of them can quantitatively optimize certain indices during their supervisor synthesis process. This causes unnecessary control limitations and often leads to high implementation cost. In the framework of Petri nets, this paper proposes a method to synthesize a cost-effective supervisor with the aid of a set of mathematical programming formulations. Along the same vein, we also show some results by investigating timed Petri nets, which can be utilized to make a good tradeoff between implementation cost and system cycle time. Examples are used to validate the effectiveness of our result.

This paper presents an approach to modeling aircraft airline maintenance circuit through a particular Petri Nets structures, called Treble transitions Petri Nets. In order to meet the requirements of the simulation of aircraft airline maintenance circuit, several enhancements were proposed. The first of them consider the characteristic of circuit, the places, transitions and arcs of classical Petri Nets are extended. In the Second enhancement, the rules of transitions were modified. Finally, the relating matrix and the state transfer equation are redefined. One case is included illustrating the applicability and efficiency of the proposed modeling method.

Logical modelling and Petri nets constitute two complementary approaches for the dynamical modelling of biological regulatory networks. Leaning on a translation of logical models into standard Petri nets, we propose a formalisation of the notion of circuit functionality in the Petri net framework. This approach is illustrated with the modelling and analysis of a molecular regulatory network involved in the control of Th-lymphocyte differentiation.

To cope with the complexities of flexible manufacturing system FMS scheduling, this paper proposes and evaluates an improved search strategy and its application to FMS scheduling in a Petri net framework. Petri nets can concisely model multiple lot sizes for each job, the strict precedence constraint, multiple kinds of resources and concurrent activities. On the execution of the Petri nets, our algorithm can use both admissible heuristic functions and nonadmissible heuristic functions having the upper supports of the relative errors in A * heuristic search algorithm. In addition, the search scheme can ensure the results found are optimal and invokes quicker termination conditions. To demonstrate it, the scheduling results are derived and evaluated through a simple FMS with multiple lot sizes for each job. The algorithm is also applied to a set of randomly-generated FMSs with such characteristics as multiple resources and alternative routings.

In this paper we introduce an approach for defining semantics for AUML agent interaction protocol diagrams using Petri net code structures. This approach is based on the usage of net components which provide basic tasks and the structure for Petri nets. Agent interaction protocol diagrams are used to model agent conversations on an abstract level. By mapping elements of the diagrams to net components we are able to translate the diagrams into Petri nets, i.e to generate code structures from the drawings. We provide tool support for this approach by combining a tool for net components with a tool for drawing agent interaction protocol diagrams. This combined tool is available as a plug-in for Renew (Reference Net Workshop).Keywordsagentsagent interaction protocolsAUML Capa high-level Petri nets Mulan net componentsoperational semanticsreference nets Renew

An integrated autonomous control mechanism to optimize sharing of multiple resources in Simultaneous Multi-Threading processors

Many tools for online collaboration, information and file sharing are currently employed to facilitate the process of online education. However, as stated in [14] the existing E-learning environments are not mature enough and only a small set of them provide functionality for defining reusable learning entities, reliable publishing and republishing mechanisms and possibilities for the teachers to give feedback to or receive feedback from the E-students. In order to improve E-learning experience [14] presents PeU 2.0, a system that enables the graphical representation and editing of the learning workflow without the execution environment of a workflow management system. The present paper examines the current executability of Petri Nets and gives a mapping of the visual elements in the PeU 2.0 graphs onto Petri Net structures. An interesting approach is introduces for the physical execution of the Petri Nets.

A new heuristic search approach for scheduling two classes of flexible manufacturing systems (FMSs) that contains assembly operations is proposed. The FMSs are modeled by two classes of Petri nets, called generalized symmetric and asymmetric nets. In the paper, the problem of minimizing makespan is transformed into searching the reachability graph for the optimal (minimal time) firing sequence from the initial marking (state) to the goal marking. A solution of the state equation constitutes a part of the heuristic function. The dynamic information of the nets, such as concurrency and synchronization, is used to adjust the heuristic function since the solution of the state equation may over-estimate the real cost.

Individuals, populations and fluid approximations: A Petri net based perspective