9 research outputs found

    Modeling and analysis of hybrid supervisory systems.

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    Sistemas Supervisórios Híbridos podem ser definidos como sistemas de controle cujos estados são representados por variáveis discretas e contínuas, e cuja dinâmica é determinada em função do tempo e da ocorrência de eventos discretos. O desenvolvimento desta classe de Sistemas Supervisórios pode ser dividido em duas fases. A 1ª Fase consiste na elaboração de um modelo protótipo para o Sistema Supervisório, que é descrito usando um formalismo, e que é validado com base nas especificações do problema. Na 2ª Fase, este modelo, já validado, é convertido na linguagem de programação do Sistema Supervisório propriamente dito. Esta tese concentra-se na 1ª Fase, para qual abordam-se três questões principais: (1) a escolha do formalismo de modelagem; (2) como construir o modelo do Sistema Supervisório Híbrido usando este formalismo; e (3) como validar o Sistema Supervisório Híbrido usando o modelo construído. Para questão (1), introduz-se um novo formalismo de modelagem baseado na aplicação dos conceitos de Orientação a Objetos (OO) às redes Predicado Transição Diferenciais (redes PTD). Este novo formalismo é chamado de redes PTD-OO. No que se refere a questão (2), é proposto um procedimento para obtenção do modelo do Sistema Supervisório em redes PTD-OO usando os diagramas da UML (Unified Modeling Language). Finalmente, para a questão (3), o problema de validação é abordado através da definição de um conjunto de propriedades que o modelo em redes PTD-OO deve respeitar afim de que sejam garantidos os requisitos do Sistema Supervisório. Estas propriedades são, então, verificadas através de um procedimento proposto para análise de redes PTD-OO.Hybrid Supervisory Systems can be described as control systems with states that are represented by both discrete and continuous variables. Their dynamics are function of time and depend also on the occurrence of discrete events. The development of Hybrid Supervisory Systems can be divided in two phases. In the 1st Phase, a prototype-model for the Supervisory System is described using a specific formalism and is validated based on the system requirements. In the 2nd Phase, this validated model is converted to the programming language of the Supervisory System. This thesis is focused on the 1st Phase of Hybrid Supervisory System development. It approaches three main issues: (1) the choice of the modelling formalism; (2) how to build the Hybrid Supervisory System model using this formalism; and (3) how to validate the Hybrid Supervisory System using this model. For issue (1), a new modelling formalism is introduced based on Differential Predicate Transition nets (DPT nets) and object-oriented (OO) paradigm. This new formalism is called DPT-OO net. Then, for the issue (2), a modelling procedure that assists the building of the DPT-OO net model using Unified Modelling Language (UML) diagrams is proposed. Finally, for the issue (3), the validation problem is approached by defining a set of properties of the DPT-OO net model that assures the Supervisory System requirements. These properties are then formally verified using a proposed analysis procedure

    A PETRI NET BASED PLATFORM FOR DISTRIBUTED MODELING AND SIMULATION OF PRODUCTIVE SYSTEMS

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    Abstract. Currently with the increasing complexity of productive systems associated with the geographical dispersion of industries there are new requiriments for design tools. In this context the purpose of this work is to introduce a new platform for distributed modeling and analysis of productive systems. The platform is based on Petri net as a modeling formalism and on the label-ring protocol for managing the distributed simulation. The focus of this paper is on the platform communication algorithm. An example is presented in order to illustrate the proposal. Keywords: Petri Net, Distributed Simulation, Productive Systems. 1

    THE DEVELOPMENT OF A PLATFORM TO SIMULATE PRODUCTIVE SYSTEMS IN A DISTRIBUTED ENVIRONMENT

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    Abstract. Pushed by the need of enlarging productive systems, the use of open distributed automation concept is spreading in industry. In distributed systems, some activities, such as the network data transmission may be seen as a succession of discrete states and instantaneous events. In this case, Petri Nets may be used to model this kind of system because it is known as a powerful tool used to model and to analysis concurrent, distributed, asynchronous, and parallel systems and it has a useful graphic representation and mathematic formalism. This work proposes the development of a platform to model and simulate productive systems, in a distributed computers environment. The adoption of middleware systems in this platform guaranties more portability, interoperability, scalability, and interconnectivity, allowing a future integration of this platform with real machines/resources. To help on the design of this platform, both ODP (Open and Distributed Processing) and UML (Unified Modeling Language) diagrams are used

    From natural language standard documents to state machines : advantages and drawbacks

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    Problems in requirements documents are among the root cause of a number of accidents in space missions. A common approach toward the minimization of these problems is to transform the requirements into models that represent the system’s behavior. However, this solution requires dealing with issues such as choosing the best modeling formalism, defining to what extent the transformation process should be automated, and assuring the quality of the requirements documents to be used as input. In space missions, requirements are frequently tailored from standard documents, such as the Packet Utilization Standard, which are composed of mandatory and optional requirements. This paper presents a semi-automatic method to transform standard requirements documents into extended finite state machines. To evaluate it, we apply the method to a set of requirements from the Packet Utilization Standard. We evaluate the method using some Packet Utilization Standard services. In light of the results, the paper discusses advantages and potential problems of each approac

    NEOTROPICAL CARNIVORES: a data set on carnivore distribution in the Neotropics

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    Mammalian carnivores are considered a key group in maintaining ecological health and can indicate potential ecological integrity in landscapes where they occur. Carnivores also hold high conservation value and their habitat requirements can guide management and conservation plans. The order Carnivora has 84 species from 8 families in the Neotropical region: Canidae; Felidae; Mephitidae; Mustelidae; Otariidae; Phocidae; Procyonidae; and Ursidae. Herein, we include published and unpublished data on native terrestrial Neotropical carnivores (Canidae; Felidae; Mephitidae; Mustelidae; Procyonidae; and Ursidae). NEOTROPICAL CARNIVORES is a publicly available data set that includes 99,605 data entries from 35,511 unique georeferenced coordinates. Detection/non-detection and quantitative data were obtained from 1818 to 2018 by researchers, governmental agencies, non-governmental organizations, and private consultants. Data were collected using several methods including camera trapping, museum collections, roadkill, line transect, and opportunistic records. Literature (peer-reviewed and grey literature) from Portuguese, Spanish and English were incorporated in this compilation. Most of the data set consists of detection data entries (n = 79,343; 79.7%) but also includes non-detection data (n = 20,262; 20.3%). Of those, 43.3% also include count data (n = 43,151). The information available in NEOTROPICAL CARNIVORES will contribute to macroecological, ecological, and conservation questions in multiple spatio-temporal perspectives. As carnivores play key roles in trophic interactions, a better understanding of their distribution and habitat requirements are essential to establish conservation management plans and safeguard the future ecological health of Neotropical ecosystems. Our data paper, combined with other large-scale data sets, has great potential to clarify species distribution and related ecological processes within the Neotropics. There are no copyright restrictions and no restriction for using data from this data paper, as long as the data paper is cited as the source of the information used. We also request that users inform us of how they intend to use the data
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