First-order Hybrid Petri Nets Research Articles

Hybrid Petri Nets to Re-design Low-Automated Production Processes: the Case Study of a Sardinian Bakery

This paper shows the practical relevance of first-order hybrid Petri nets in the re-design process of low-automated production systems. In particular, we analyze the case study of a bakery producing “pane Carasau”, a typical Sardinian bread, whose traditional production plant currently has difficulties in coping with the constant increase in market demand. Through first-order hybrid Petri nets, the current functioning and the operating features and dynamics of the case study are modelled, waste sources and bottlenecks are detected, and alternative re-designed scenarios are implemented and evaluated to identify the most suitable reengineering actions to be developed.

Modelling and simulation of energy consumption of ceramic production chains with mixed flows using hybrid Petri nets

Ceramic production chain consisting of discrete flow and continuous flow energy-intensive processes consumes substantial amounts of energy. This study aims to evaluate energy consumption performance and energy-saving potentials of the ceramic production chain. According to the energy consumption characteristics of manufacturing processes and process interaction constraints in a ceramic production chain, an approach integrating the first-order hybrid Petri net (FOHPN) model, an objective linear programming model and a sensitivity analysis is proposed. The FOHPN model will simulate the energy consumption patterns of the ceramic production chain. Meanwhile, multi-objective linear programming model and sensitivity analysis will suggest the optimal specific energy consumption (SEC) of the production chain and identify the influences of input parameters (i.e. production rate of a process) on the SEC in the optimal production scheme. Finally, a real case study from bathroom ceramic plant validates the approach. It provides a tool for modelling and simulation of energy consumption of ceramic production chains with mixed flows and helps operators to perform energy-saving actions in the ceramic enterprise.

Fault detection and power distribution optimization of smart grids based on hybrid Petri net

Although smart grids have attracted significant researches in recent years no comprehensive model has been proposed to capture fault occurrences and power distribution optimization in such systems. In this paper a First Order Hybrid Petri Net (FOHPN) approach is proposed to model smart grids. Since smart grids are event driven systems that are comprised of continuous dynamics, FOHPN approach seems to be a logical choice for modeling and analysis of such systems. An IEEE standard 14-bus power system with actual data is used for modeling and simulation. The proposed model includes all units of smart grids along with their interactions, and it also guarantees the optimal behavior of the system regarding fault detection and power distribution. Simulation results validate both accuracy and reliability of the model.

Modeling and performance analysis of a closed-loop supply chain using first-order hybrid Petri nets

Green or closed-loop supply chain had been the focus of many manufacturers during the last decade. The application of closed-loop supply chain in today’s manufacturing is not only due to growing environmental concerns and the recognition of its benefits in reducing greenhouse gas emissions, energy consumption, and meeting a more strict environmental regulations but it also offers economic competitive advantages if appropriately managed. First-order hybrid Petri nets represent a powerful graphical and mathematical formalism to map and analyze the dynamics of complex systems such as closed-loop supply chain networks. This article aims at illustrating the use of first-order hybrid Petri nets to model a closed-loop supply chain network and evaluate its operational, financial, and environmental performance measures under different management policies. Actual data from auto manufacturer in the United States are used to validate network’s performance under both tactical and strategic decision-making, namely, (1) tactical decision—production policies: increase of recovered versus new components and (2) strategic decision—closed-loop supply chain network structure: manufacturer internal recovery process or recovery process done by a third-party collection and recovery center. The work presented in this article is an extension of the use of first-order hybrid Petri nets as a modeling and performance analysis tool from supply chain to closed-loop supply chain. The modularity property of first-order hybrid Petri nets has been used in the modeling process, and the simulation and analysis of the modeled network are done in MATLAB® environment. The results of the experiments depict that first-order hybrid Petri nets are a powerful modeling and analysis formalism for closed-loop supply chain networks and can be further used as an efficient decision-making tool at both tactical and strategic levels. Unlike other researches on modeling supply chain networks that focus on evaluating individually cost, operational, or environmental aspects, the research here shows how first-order hybrid Petri nets can be extended to assess simultaneously operational, financial, and environmental network’s performance measures at different managerial decision-making levels. The results particularly are compelling for researchers and industrial practitioners who can use the same methodology in evaluating their network’s performance and making educated management decisions based on the performance results and the impact of their selected supply chain and manufacturing strategies.

Management of Intermodal Freight Terminals by First-Order Hybrid Petri Nets

In this paper, we show how first-order hybrid Petri nets can be efficiently used to model and manage intermodal freight transport terminals. The proposed formalism enables the terminal decision maker to choose the speeds associated with continuous transitions in order to optimize the terminal performance by two alternative control policies: the container flows maximization and the minimization of the residual containers in the storage area. The approach may be used either offline, to take decisions on the terminal resources, or online, to solve congestions/malfunctions. A real case study is modeled and managed by the proposed optimal control policies.

Decomposition of first-order hybrid Petri nets for hierarchical control of manufacturing systems

Although hybrid Petri net (HPN) is a popular formalism in modelling hybrid production systems, the HPN model of large scale systems gets substantially complicated for analysis and control due to large dimensionality of such systems. To overcome this problem, a typical approach is to decompose the net into subnets and then control the plant through hierarchical or decentralized structures. Although this concept has been widely discussed in the literature for discrete PNs, there is a lack of research for HPNs. In this paper, a new method of decomposition of first-order hybrid Petri nets (FOHPNs) is proposed first and then the hierarchical control of the subnets through a coordinator is introduced. The advantage of using the proposed approach is validated by an existing example. A sugar milling case study is analysed by using a decomposed FOHPN model and the optimization results are compared against the results of the approaches presented in other papers. Simulation results show not only an improvement in production rate, but also show the ability to control the plant online. In addition, by using the hierarchical control structure for an FOHPN model, it is possible to reduce the cost of communication links, improve the reliability of the system, maintain the plant locally, and partially redesign the system.

Agent-based modelling of the evacuation of endangered areas in crisis situations

The evacuation process from endangered areas (EA) into safe spaces in crisis situations is modelled by means of simple agents (gate-ways equipped by sensors). Petri nets (PN) are utilized here to model the EA structure as well as the agents and their cooperation. More precisely, timed PN (TPN) and first-order hybrid PN (FOHPN) are used to do this. Rooms, other spaces to be evacuated (corridors) and the safe spaces out of EA (where people are evacuated) are modelled by TPN places and FOHPN continuous places. Gate-ways are modelled by TPN subnets and by FOHPN continuous transitions. While the supervisor for the TPN gate-ways can be synthesized by means of place/transition PN (P/T PN), the blocks of FOHPN discrete places and transitions are used to affect the gate-ways. Depending on the immediate throughput of the gate-ways the escape time behaviour is found in the process of simulation. This paper is the extended version of the paper (Capkovia? Intelligent Information and Database Systems. LNAI. Springer, Cham Heidelberg 2014) presented in the ACIIDS 2014 conference.

Freeway Traffic Modeling and Control in a First-Order Hybrid Petri Net Framework

The paper presents a model for freeway traffic performance evaluation and control in a First-Order Hybrid Petri Net (FOHPN) framework. Such a hybrid Petri net formalism includes continuous places holding fluid, discrete places containing a non-negative integer number of tokens and transitions, which are either discrete or continuous. In order to suitably describe the dynamics of the freeway traffic flow, we allow updating the transition firing speed as a function of the markings modeling the freeway traffic, as described by the stationary flow-density relationship. Moreover, we propose an online optimal control coordination of speed limits with the objective of maximizing the flow density. The use of FOHPNs offers several significant advantages with respect to the model existing in the related literature: the graphical feature enables an easy modular modeling approach and the mathematical aspects efficiently allow simulating and optimizing the system. The effectiveness of the FOHPN formalism is shown by applying the proposed modeling and control technique to a stretch of a freeway in the North-East of Italy, where a solution of an accident situation is considered.

An Improved Freeway Traffic Model in a First Order Hybrid Petri Net Framework

The paper presents a model for traffic state estimation and management of the freeways. The model is based on First-Order Hybrid Petri Nets (FOHPNs), a hybrid Petri net formalism including continuous places holding fluid, discrete places containing a non-negative integer number of tokens and transitions, which are either discrete or continuous. The paper improves a previous model in order to suitably describe the dynamics of the freeway traffic flow. To this aim we modify the dynamics of the FOHPN and we allow updating the transition firing speed as a function of the markings modeling the freeway traffic. The obtained model is a linear discrete-time, time-varying state variable model and is suitable to describe a hybrid system such as a freeway subject to unpredictable events (i.e., accidents or bottlenecks). The effectiveness of the FOHPN formalism is shown by applying the proposed modeling technique to a stretch of a freeway in the North-East of Italy.

Dynamic Modeling of Carbon Flow for Mechanical Manufacturing System Based on Extended First-order Hybrid Petri Nets

Mechanical manufacturing system is a strongly coupled system of production and energy.In view of its coupling characteristics,a dynamic modeling method of carbon flow based on extended first-order hybrid Petri nets is proposed.The dynamic characteristics of carbon flow are analyzed for mechanical manufacturing system,and its corresponding system boundary is established.Production structure and operating model of maufacturing system,balance equations of energy and material and the formula for calculating the carbon emissions are derived from the system boundary,laying a quantitative analysis foundation for the following model.With respect to the continuity of energy and the impact of discrete state on the continuous processes,based on the original first-order hybrid Petri nets,controllable arcs and inhibitor arcs are introduced in order to enhance the modeling semantics,and the formal definition and rules explanation of the model are given.The model is applied to a manufacturing system automatic production line.The multi-objective function is established with the constraints,the time domain characteristics of the energy flow,material flow are simulated and optimized,and the corresponding carbon emissions are calculated.The method lays a theoretical foundation for the enterprises to carry out low-carbon manufacturing.

A First-Order Hybrid Petri Net Model for Supply Chain Management

A supply chain (SC) is a network of independent manufacturing and logistics companies that perform the critical functions in the order fulfillment process. This paper proposes an effective and modular model to describe material, financial and information flow of SCs at the operational level based on first-order hybrid Petri nets (PNs), i.e., PNs that make use of first-order fluid approximation. The proposed formalism enables the SC designer to choose suitable production rates of facilities in order to optimize the chosen objective function. The optimal mode of operation is performed based on the state knowledge of the obtained linear discrete-time, time-varying state variable model in order to react to unpredictable events such as the blocking of a supply or an accident in a transportation facility. A case study is modeled in the proposed framework and is simulated under three different closed-loop control strategies.

A fault monitor for automated manufacturing systems using a hybrid Petri nets formalism

Fault monitoring is an essential requirement for safety and reliability of industrial systems. The paper presents a novel event-based online monitoring technique for automated manufacturing systems, ensuring timely and accurate detection of system failures. The monitor model is based on first-order hybrid Petri nets, ie, Petri nets that make use of first-order fluid approximation. The proposed fault analysis technique relies on a modular framework, so that elementary monitors can be connected with other monitors to check more complex systems while avoiding the state—space explosion problem. In addition, the presented monitor detects system faults as soon as possible, before the maximum execution time assigned to each task. Several examples and an application to an automated manufacturing system proposed in the related literature enlighten the simplicity and modularity of the technique.

First-order hybrid Petri nets. An application to distributed manufacturing systems

In this paper we consider Hybrid Petri Nets (HPNs), a particular formalism that combines fluid and discrete event dynamics. We first provide a survey of the main HPN models that have been presented in the literature in the last decades. Then, we focus on a particular HPN model, namely the First-Order Hybrid Petri Net (FOHPN) model, whose continuous dynamics are piece-wise constant. Here the problem of designing an optimal controller simply requires solving on-line an appropriate linear integer programming problem. In this paper we show how FOHPNs can efficiently represent the concurrent activities of Distributed Manufacturing Systems (DMS), and some interesting optimization problems are also solved via numerical simulation.

Modelling and simulation of a bottling plant using hybrid Petri nets

In this paper we use First–Order Hybrid Petri nets (FOHPN), an hybrid model that combines fluid and discrete event dynamics, to model the concurrent activities of manufacturing systems. In particular we consider an existing mineral water bottling plant and we show how the FOHPN model is extremely suited to describe the high-throughput production lines, that are one of the main components in the considered plant. Some variations with respect to the previous definition of the FOHPN model are also introduced here to better describe the behavior of the conveyor lines. Finally, we show that, thanks to the fluid approximation of some discrete-event dynamics, the considered plant may also be efficiently simulated using FOHPN. This also enabled us to identify, among the most commonly used configurations of the plant, which are the optimal working conditions in terms of maximal throughput and net profit.

Modelling and simulation of manufacturing systems with first-order hybrid Petri nets

First-order hybrid Petri nets are models that consist of continuous places holding fluid, discrete places containing a non-negative integer number of tokens, and transitions, either discrete or continuous. In the first part of the paper, we provide a framework to describe the overall hybrid net behaviour that combines both time-driven and event-driven dynamics. The resulting model is a linear discrete-time, time-varying state variable model that can be directly used by an efficient simulation tool. In the second part of the paper, we focus on manufacturing systems. Manufacturing systems are discrete-event dynamic systems whose number of reachable states is typically very large, hence approximating fluid models have often been used in this context. We describe the net models of the elementary components of a flexible manufacturing system (machines and buffers) and we show in a final example how these modules can be put together in a bottom-up fashion.

First-order hybrid Petri nets: a model for optimization and control

We consider in this paper first-order hybrid Petri nets, a model that consists of continuous places holding fluid, discrete places containing a nonnegative integer number of tokens, and transitions, either discrete or continuous. We set up a linear algebraic formalism to study the first-order continuous behavior of this model and show how its control can be framed as a conflict resolution policy that aims at optimizing a given objective function. The use of linear algebra leads to sensitivity analysis that allows one to study of how changes in the structure of the model influence the optimal behavior. As an example of application, we show how the proposed formalism can be applied to flexible manufacturing systems with arbitrary layout and different classes of products.

A linear state variable model for first-order hybrid petri nets

First-Order Hybrid Petri Nets are a model that consists of continuous places holding fluid, discrete places containing a non-negative integer number of tokens, and transitions, either discrete or continuous. This paper provides a framework to describe the overall hybrid net behavior that combines both time-driven and event-driven dynamics. The resulting model is a linear discrete-time time-varying state variable model, that can be directly used by an efficient simulation tool.