On Structuring Events for IOPT Net Models

Part 9: Embedded Systems and Petri NetsInternational audienceThis paper presents a proposal for structuring events for system models expressed using IOPT nets (Input-Output Place-Transition Petri nets). Currently, a non-autonomous event within an IOPT model is defined based on change of input signals with respect to a specific threshold, when two consecutive execution steps are considered. New types of events are proposed allowing the definition of an event activated not only by crossing a fixed threshold, but also considering a change in associated signal value on a specific amount (belonging to an interval of values). The concept is further extended allowing the definition of an event based on signal values presented on previous execution steps. The proposal results on a classification of several types of events, namely threshold events, momentum events, impetus events, as well as delayed events and logical events. Usage of these types of events allows improvements in terms of expressiveness and compactness of the resulted model

The DS-Pnet modeling formalism for cyber-physical system development

This work presents the DS-Pnet modeling formalism (Dataflow, Signals and Petri nets), designed for the development of cyber-physical systems, combining the characteristics of Petri nets and dataflows to support the modeling of mixed systems containing both reactive parts and data processing operations. Inheriting the features of the parent IOPT Petri net class, including an external interface composed of input and output signals and events, the addition of dataflow operations brings enhanced modeling capabilities to specify mathematical data transformations and graphically express the dependencies between signals. Data-centric systems, that do not require reactive controllers, are designed using pure dataflow models. Component based model composition enables reusing existing components, create libraries of previously tested components and hierarchically decompose complex systems into smaller sub-systems. A precise execution semantics was defined, considering the relationship between dataflow and Petri net nodes, providing an abstraction to define the interface between reactive controllers and input and output signals, including analog sensors and actuators. The new formalism is supported by the IOPT-Flow Web based tool framework, offering tools to design and edit models, simulate model execution on the Web browser, plus model-checking and software/hardware automatic code generation tools to implement controllers running on embedded devices (C,VHDL and JavaScript). A new communication protocol was created to permit the automatic implementation of distributed cyber-physical systems composed of networks of remote components communicating over the Internet. The editor tool connects directly to remote embedded devices running DS-Pnet models and may import remote components into new models, contributing to simplify the creation of distributed cyber-physical applications, where the communication between distributed components is specified just by drawing arcs. Several application examples were designed to validate the proposed formalism and the associated framework, ranging from hardware solutions, industrial applications to distributed software applications

Requirements Specification for Controller Design-from Use Cases to IOPT Net Models

12th IEEE International Conference on Industrial Informatics, INDIN , Porto Alegre: Jul 27-30, 2014Non-autonomous Petri nets offer a language especially adapted for controller specifications. They are typically used in the design phase often with no clear connection to the analysis phase, including requirements specification. This paper shows how use cases can be used to support requirements specification amenable to a direct transformation to IOPT nets, a class of non-autonomous Petri nets. To that end, we propose a set of semi-formal rules for use case descriptions, including use case relationships, which take advantage of the concepts available in IOPT nets, namely input and output signals and events and net addition, a net composition operation

Petri net based development of globally-asynchronous locally-synchronous distributed embedded systems

Dissertação para obtenção do Grau de Doutor em Engenharia Electrotécnica e de ComputadoresA model-based development approach (MBDA) for Globally-Asynchronous Locally- Synchronous (GALS) Distributed Embedded Systems (DESs) is proposed. This approach relies on the GALS-DESs specification through (low- or high-level) Petri net classes, which ensure that the created models are GALS, locally deterministic, distributable, networkindependent, and platform-independent and support their simulation, verification, and implementation (using simulation, model-checking, and code generation tools). The use of network- and platform-independent models enable the use of heterogeneous communication networks to support the distributed components interaction and enable the use of heterogeneous platforms to support the components and the communication nodes implementation. To enable the proposed MBDA, Petri nets are extended with a set of the concepts, most notably time-domains and asynchronous-channels. Algorithms to support the verification of GALS-DES models and their decomposition into implementable sub-models are also proposed. A tool chain framework (IOPT-tools) was extended with this work proposals, supporting their validation and the GALS-DESs development.Fundação para a Ciência e a Tecnologia - grant ref. SFRH/BD/62171/200

Petri net model decomposition - a model based approach supporting distributed execution

Dissertação apresentada para obtenção do Grau de Doutor em Engenharia Electrotécnica, Especialidade de Sistemas Digitais, pela Universidade Nova de Lisboa, Faculdade de Ciências e TecnologiaModel-based systems development has contributed to reducing the enormous difference between the continuous increase of systems complexity and the improvement of methods and methodologies available to support systems development. The choice of the modeling formalism is an important factor for success-fully increasing productivity. Petri nets proved to be a suitable candidate for being chosen as a system specification language due to their natural support of modeling processes with concurrency, synchronization and resource sharing, as well as the mechanisms of composition and decomposition. Also having a formal representation reinforces the choice, given that the use of verification tools is fundamental for complex systems development. This work proposes a method for partitioning Petri net models into concurrent sub-models, supporting their distributed implementation. The IOPT class (Input-Output Place Transition) is used as a reference class. It is extended by directed synchronous communication channels, enabling the com- munication between the generated sub-models. Three rules are proposed to perform the partition, and restrictions of the proposed partition method are identified. It is possible to directly compose models which result from the partitioning operation, through an operation of model addition. This allows the re-use of previously obtained models, as well as the easy modification of the intended system functionalities. The algorithms associated with the implementation of the partition operation are presented, as well as its rules and other procedures. The proposed methods are validated through several case studies emphasizing control components of automation systems

Refining IOPT Petri Nets Class for Embedded System Controller Modeling

Since its inception, the Input-Output Place-Transition (IOPT) class of Petri nets have changed in response to the gained experience in the use of its associated tools freely available as a cloud based toolset. Here, we informally present the current state of the IOPT net class as supported by the IOPT-Tools, publicly available at http://gres.uninova.pt/IOPT-Tools/. The corresponding formal syntax and semantics are presented, followed by an illustrative example. Finally, we give a brief presentation of the respective XML-based interchange format and conclude

Petri nets based components within globally asynchronous locally synchronous systems

Dissertação apresentada na Faculdade de Ciências e Tecnologias da Universidade Nova de Lisboa para a obtenção do grau de Mestre em Engenharia Electrotécnica e ComputadoresThe main goal is to develop a solution for the interconnection of components constituent of a GALS - Globally Asynchronous, Locally Synchronous – system. The components are implemented in parallel obtained as a result of the partition of a model expressed a Petri net (PN), performed using the PNs editor SNOOPY-IOPT in conjunction with the Split tool and the tools to automatically generate the VHDL code from the representations of the PNML models resulting from the partition (these tools were developed under the project FORDESIGN and are available at http://www.uninova.pt/FORDESIGN). Typical solutions will be analyzed to ensure proper communication between components of the GALS system, as well as characterized and developed an appropriate solution for the interconnection of the components associated with the PN sub-models. The final goal (not attained with this thesis) would be to acquire a tool that allows generation of code for the interconnection solution from the associated components, considering a specific application. The solution proposed for componentes interconnection was coded in VHDL and the implementation platforms used for testing include the Xilinx FPGA Spartan-3 and Virtex-II

FPGA in image processing supported by IOPT-Flow

Image processing is widely used in the most diverse industries. One of the tools widely used to perform image processing is the OpenCV library. Although the implementation of image processing algorithms can be made in software, it is also possible to implement image processing algorithms in hardware. In some cases, the execution time can be smaller than the execution time achieved in software. This work main goal is to evaluate the use of VHDL, DS-Pnets, and IOPT-Flow to develop image processing systems in hardware, in FPGA-based platforms. To enable it, a validation platform was developed. A set of image processing algorithms were specified, during this work, in VHDL and/or in DS-Pnets. These were validated using the IOPT-Flow validation tool and/or the Xilinx ISE Simulator. The automatic VHDL code generator from IOPT-Flow framework was used to translate DS-Pnet models into the implementation code. The FPGA-based implementations were compared with software implementations, supported by the OpenCV library. The created DS-Pnet models were added into a folder of the IOPT-Flow editor, to create an image processing library. It was possible to conclude that the DS-Pnets and their associated tools, IOPT-Flow tools, support the development of image processing systems. These tools, which simplify the development of image processing systems, are available online at http://gres.uninova.pt/iopt-flow/

Geração automática de código ANSI C a partir de Redes de Petri IOPT - PNML2C -

Dissertação apresentada na Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa para obtenção do Grau de Mestre em Engenharia Electrotécnica e de ComputadoresNesta dissertação apresenta-se a elaboração de regras de tradução e o desenvolvimento de uma ferramenta de geração de código na Linguagem ANSI C a partir de Redes de Petri IOPT especificadas em PNML. As redes de Petri IOPT resultam da extensão das redes de Petri Lugar-Transição com algumas características não autónomas,como sinais e eventos de entrada e saída. Para cada característica dos modelos expressos em Redes de Petri IOPT são definidas as estruturas necessárias em ANSI C para a sua execução, de forma a garantir a semântica pretendida. A ferramenta desenvolvida recebe o modelo do controlador expresso através de um modelo IOPT através de um ficheiro no formato PNML, ao qual foram adicionadas as representações dos elementos específicos das redes IOPT. O modelo é analisado e é criado um conjunto de cinco ficheiros preparados para, apenas com a definição do interface com a plataforma de implementação, executar a rede de acordo com a semântica definida. Foram criados dois interfaces para a ferramenta, um gráfico para ser usado por humanos e outro por comandos para facilitar a integração com outras ferramentas. Criou-se ainda uma nova ferramenta com o mesmo objectivo mas utilizando um novo meta-modelo das Redes de Petri IOPT de forma a tratar as alterações introduzidas por este meta-modelo. As ferramentas desenvolvidas foram validadas através de exemplos de sistemas de automação

Technological Innovation for the Internet of Things: 4th IFIP WG 5.5/SOCOLNET Doctoral Conference on Computing, Electrical and Industrial Systems, DoCEIS 2013, Costa de Caparica, Portugal, April 15-17, 2013. Proceedings

International audienceBook Front Matter of AICT 39