Academic literature on the topic 'Colored modified hybrid Petri nets'

Petri nets are a discrete event simulation approach developed for system representation, in particular for their concurrency and synchronization properties. Various extensions to the original theory of Petri nets have been used for modeling molecular biology systems and metabolic networks. These extensions are stochastic, colored, hybrid and functional. This paper carries out an initial review of the various modeling approaches based on Petri net found in the literature, and of the biological systems that have been successfully modeled with these approaches. Moreover, the modeling goals and possibilities of qualitative analysis and system simulation of each approach are discussed.

A modification of the Petri nets is proposed  a Fuzzy Colored Petri Net (FCPN), leading to the integration of Fuzzy Petri Nets (FPN) and Colored Petri Nets (CPN). Separately, the shortcomings of FPN and CPN and the advantages the developed FCPN for modeling intelligent control systems are identified and justified. In the developed modified FCPN the membership functions of the terms of a linguistic variable are applied to markers of the CPN as color and fuzzy existence conditions are assigned to arcs depending on the values of the linguistic variable. As a result, FCPN with enhanced capabilities was obtained, which eliminates the shortcomings of CPN and FPN. The FCPN and a simulation approach are defined, which includes a reasoning algorithm, as well as a detailed procedure for modeling and analysis of nonlinear discrete objects. The structure is organized in the CPN Tools system with the synchronization of the CPN ML (Markup Language) language with the MatLab package. The choice of membership function and fuzzification of term values is performed in the Fuzzy Toolbox application of the MatLab system. The proposed approach is illustrated by simple example, including the control of water pumps, to maintain the required water level in the pumping well. A model is developed for the automation of adaptive fuzzy control of water pumps based on modified FCPN. Based on the criteria for the operation of water pumps according to the water levels in the pumping well, many positions and transitions of the FCPN are formed. Describing the necessary behavior of the system by the relations between the positions and transitions of the FCPN using the logic “If ... Then ...” an adaptation algorithm is developed. Based on the algorithm, the matrices of input and output incidents are determined. The graph model of the FCPN is developed. Visualization of the model is implemented in the CPN Tools system. The computer simulations and net analysis experiments demonstrate the convenience of the developed approach when modeling the intelligent control of dynamic systems.

A modification of the Petri nets is proposed  a Fuzzy Colored Petri Net (FCPN), leading to the integration of Fuzzy Petri Nets (FPN) and Colored Petri Nets (CPN). Separately, the shortcomings of FPN and CPN and the advantages the developed FCPN for modeling intelligent control systems are identified and justified. In the developed modified FCPN the membership functions of the terms of a linguistic variable are applied to markers of the CPN as color and fuzzy existence conditions are assigned to arcs depending on the values of the linguistic variable. As a result, FCPN with enhanced capabilities was obtained, which eliminates the shortcomings of CPN and FPN. The FCPN and a simulation approach are defined, which includes a reasoning algorithm, as well as a detailed procedure for modeling and analysis of nonlinear discrete objects. The structure is organized in the CPN Tools system with the synchronization of the CPN ML (Markup Language) language with the MatLab package. The choice of membership function and fuzzification of term values is performed in the Fuzzy Toolbox application of the MatLab system. The proposed approach is illustrated by simple example, including the control of water pumps, to maintain the required water level in the pumping well. A model is developed for the automation of adaptive fuzzy control of water pumps based on modified FCPN. Based on the criteria for the operation of water pumps according to the water levels in the pumping well, many positions and transitions of the FCPN are formed. Describing the necessary behavior of the system by the relations between the positions and transitions of the FCPN using the logic “If ... Then ...” an adaptation algorithm is developed. Based on the algorithm, the matrices of input and output incidents are determined. The graph model of the FCPN is developed. Visualization of the model is implemented in the CPN Tools system. The computer simulations and net analysis experiments demonstrate the convenience of the developed approach when modeling the intelligent control of dynamic systems.

For the development of modern complex production processes in Industry 4.0, it is appropriate to effectively use advanced mathematical models based on Petri nets. Due to their versatility in modeling discrete-event systems, Petri nets are an important support in creating new platforms for digitized production systems. The main aim of the proposed article is to design a new software tool for modeling and control of discrete-event and hybrid systems using Arduino and similar microcontrollers. To accomplish these tasks, a new tool called PN2ARDUINO based on Petri nets is proposed able to communicate with the microcontroller. Communication with the microcontroller is based on the modified Firmata protocol hence, the control algorithm can be implemented on all microcontrollers that support this type of protocol. The developed software tool was successfully verified in control of laboratory systems. In addition, it can be used for education and research purposes as it offers a graphical environment for designing control algorithms for hybrid and mainly discrete-event systems. The proposed software tool can improve education and practice in cyber-physical systems (Industry 4.0).

The invention of reconfigurable manufacturing systems (RMSs) has created a challenging problem: how to quickly and effectively modify an RMS to address dynamic changes in a manufacturing system, such as processing failures and rework, machine breakdowns, addition of new machines, addition of new products, removal of old machines, and changes in processing routes induced by the competitive global market. This paper proposes a new model, the intelligent colored token Petri net (ICTPN), to simulate dynamic changes or reconfigurations of a system. The main idea is that intelligent colored tokens denote part types that represent real-time knowledge about changes and status of a system. Thus, dynamic configurations of a system can be effectively modeled. The developed ICTPN can model dynamic changes of a system in a modular manner, resulting in the development of a very compact model. In addition, when configurations appear, only the changed colored token of the part type from the current model has to be modified. Based on the resultant ICTPN model, deadlock-free, conservative, and reversible behavioral properties, among others, are guaranteed. The developed ICTPN model was tested and validated using the GPenSIM tool and compared with existing methods from the literature.

The International Maritime Organization regulations on the reduction of greenhouse gas emissions (GHGs) from ships require efficient dealing with this complex techno-economic and highly political problem through joint efforts of all major stakeholders from the shipbuilding industry and ship operations. The key problems of any research in the field of renewable energy, including power generation, storage, transformation and distribution, and the issues associated with limited power generation for specific loads, are the same issues that are experienced in the implementation of electric distribution technologies onboard ships. This paper analyses the effects of efficient shipping using the solar panel system and batteries to ensure continuous power supply, regardless of the weather conditions. The logistics chain of this control architecture is modelled by Colored Petri Nets. The economic analysis examines the annual costs of fuel consumption, the initial capital cost, total net cost and CO2 emissions.

Petri nets are a mathematical apparatus for modelling dynamic discrete systems. Their feature is the ability to display parallelism, asynchrony and hierarchy. First was described by Karl Petri in 1962 [1,2,8]. The Petri net is a bipartite oriented graph consisting of two types of vertices - positions and transitions connected by arcs between each other; vertices of the same type cannot be directly connected. Positions can be placed by tags (markers) that can move around the network. [2] Petri Nets (PN) used for modelling real systems is sometimes referred to as Condition/Events nets. Places identify the conditions of the parts of the system (working, idling, queuing, and failing), and transitions describe the passage from one state to another (end of a task, failure, repair...). An event occurs (a transition fire) when all the conditions are satisfied (input places are marked) and give concession to the event. The occurrence of the event entirely or partially modifies the status of the conditions (marking). The number of tokens in a place can be used to identify the number of resources lying in the condition denoted by that place [1,2,8]. Coloured Petri nets (CPN) is a graphical oriented language for design, specification, simulation and verification of systems [3-6,9,15]. It is in particular well-suited for systems that consist of several processes which communicate and synchronize. Typical examples of application areas are communication protocols, distributed systems, automated production systems, workflow analysis and VLSI chips. In the Classical Petri Net, tokens do not differ; we can say that they are colourless. Unlike standard Petri nets in Colored Petri Net of a position can contain tokens of arbitrary complexity, such as lists, etc., that enables modelling to be more reliable. The article is devoted to the study of the possibilities of modelling Colored Petri nets. The article discusses the interrelation of languages of the Colored Petri nets and traditional formal languages. The Venn diagram, which the author has modified, shows the relationship between the languages of the Colored Petri nets and some traditional languages. The language class of the Colored Petri nets includes a whole class of Context-free languages and some other classes. The paper shows modelling the task synchronization Patil using Colored Petri net, which can't be modeled using well- known operations P and V or by classical Petri network, since the operations P and V and classical Petri networks have limited mathematical properties which do not allow to model the mechanisms in which the process should be synchronized with the optimal allocation of resources.

2011 - 2012
Discrete Event System (DES) are systems whose behavior is governed by discrete events occurring asynchronously over time and solely responsible for generating state transitions. DESs are particularly used in the field of the manufactured systems, handling systems and transportation systems: even if such system are being studying for long time, because of their complexity, they still present many issues that attract research interest. In particular this dissertation focuses about handling system modeling and DES identification. Obtaining a good model of a system (both time-driven and event-driven) allows to more easily execute operations as performance analysis, control, monitoring of system evolution. However, in some cases modeling of a system is not simple because of several complications due to the behavior of the system or of the context it belongs to. As example, sometimes, especially in the context of material handling and transportation, systems present both an event-driven and a time-driven behavior. In all that cases a very high accuracy is not requested it is usual neglect the latter and “looking” at the system as a DES (as example modeling a handling system it is possible to be interested in knowing if a vehicle is or not in a zone of the path while it is not important to know its exactly position). When the time-driven behavior plays a fundamental role in the obtaining the overall system performance, such dynamics cannot be neglected and they have to be explicitly modeled. This is the case, as example, of the automated warehouse systems, where the handling subsystem, as will be shown in the rest of this dissertation, presents time-driven dynamics that greatly influence the warehouse’s performance. Consequently a new way to model the system behavior has to be used. However, there are situation in which the difficult issue is not choosing the right formalism to model the system but it is the modeling itself. This is typical in many practical contexts, where it can occur that one has to work with unknown ready-made systems and no documentation about their behavior is available, or the model of a very complex system is needed. In these and other cases modeling becomes hard and another way to obtain the model of the system is needed: automated identification can be the solution. In the modeling environment, contribution of this thesis consists in presenting a new methodology to obtain a model oriented to the control and performance analysis of complex material handling systems that is highly modular, compact and made of parameterized modules. First a discrete event model is presented and then a new formalism that merges the concepts of Hybrid Petri Nets and Colored Petri Nets is introduced: the Colored Modified Hybrid Petri Nets (CMHPNs). Hence a new CMHPN model is proposed: it allows to model both the event nature and the continuous nature of the system. As more, to allow the monitoring of system evolutions, a freeware simulation tool for the CMHPNs is presented. Finally it is shown how the CMHPN model can be used to execute analysis and performance evaluation. Liveness analysis is performed by means of a hybrid automaton obtained from the net model. A deadlock prevention policy is synthesized working on an aggregated model. To prove the effectiveness of this new formalism an existing large automated warehouse system is presented as case study: its CMHPNs model is used to simulate the system behavior and to analyze the warehouse’s performance. In the identification environments, the guidelines of a new “active” approach to identify the model of a preexisting system is described. The proposed preliminary algorithm identifies a free labeled PN model on the basis of the observed output sequences and of the modifiable input consisting of the enabled controllable transitions set. The main idea is to use the knowledge of the set of enabled controllable transitions together with additional information on the conflicting transitions to accelerate the net identification with respect to the passive identification approaches. In particular, the system assumes that the maximum time that must elapse from the enabling of a transition until it fires is known and that it is possible to detect if the system is entered in a cyclic behavior. Using this additional information, it is possible to determine set of constraints to represent sequences that are not accepted by the system. Such constraints can be used to improve the net identification. [edited by author]
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