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- IOPT Petri Net State Space Generation Algorithm with Maximal-Step Execution SemanticsPublication . Pereira, Fernando; Moutinho, Filipe; Gomes, Luís; Campos-Rebelo, RogérioThis paper presents an algorithm to efficiently generate the state-space of systems specified using the IOPT Petri-net modeling formalism. IOPT nets are a non-autonomous Petri-net class, based on Place-Transition nets with an extended set of features designed to allow the rapid prototyping and synthesis of system controllers through an existing hardware-software co-design framework. To obtain coherent and deterministic operation, IOPT nets use a maximal-step execution semantics where, in a single execution step, all enabled transitions will fire simultaneously. This fact increases the resulting state-space complexity and can cause an arc "explosion" effect. Real-world applications, with several million states, will reach a higher order of magnitude number of arcs, leading to the need for high performance state-space generator algorithms. The proposed algorithm applies a compilation approach to read a PNML file containing one IOPT model and automatically generate an optimized C program to calculate the corresponding state-space.
- Remote operation of embedded controllers designed using IOPT Petri-netsPublication . Pereira, Fernando; Melo, Arildo; Gomes, LuísThis paper presents a new communication architecture to enable the remote control, monitoring and debug of embedded-system controllers designed using IOPT Petri nets. IOPT Petri nets and the related tools (http://gres.uninova.pt) have been used as a rapid prototyping and development framework, including model-checking, simulation and automatic code generation tools. The new architecture adds remote operation capabilities to the controllers produced by the automatic code generators, enabling quasi-real-time remote debugging and monitoring using the IOPT simulator tool. Furthermore, it enables the creation of graphical user interfaces for remote operation and the development of distributed systems where a Petri net model running on a central system supervises the actions of multiple remote subsystems. © 2015 IEEE.
- The IOPT-flow modeling framework applied to power electronics controllersPublication . Pereira, Fernando; Gomes, LuísThe input–output place-transition (IOPT)-flow modeling framework was created to support the design of mixed embedded system controllers containing both reactive and data-driven parts, combining Petri net and dataflow elements. The reactive parts, whose evolution depends on external events, are modeled using Petri nets. Data manipulation operations that process input signals and events are expressed using dataflows. The framework is composed by a Web-based tool-chain including a graphical editor, a simulator, and automatic code generation tools to produce C and VHDL controller implementations. To demonstrate the language and the related tools, an example of a closedloop brushless dc servo motor controller is presented. A prototype using the automatic generated VHDL code was implemented on a field-programmable gate array (FPGA) board.
- Automatic synthesis of VHDL Hardware Components from IOPT Petri Net modelsPublication . Pereira, Fernando; Gomes, LuísThe IOPT Petri net class, designed to implement embedded system controllers, combining the well known properties of Petri nets with input and output functions, provides a set of capabilities suitable to specify digital controller systems. This paper presents an automatic code generation tool used to create VHDL controller implementations of IOPT models and describes the underlying code generation strategies. The new tool is integrated under the Web based IOPT-Tools framework (accessible at http://gres.uninova.pt), containing a complete tool-chain ranging from interactive model design and edition, model checking and simulation tools to automatic code generation, allowing the design of embedded system controllers using only graphical tools and without the need to manually write any hardware description or software code.
- Multifunctional controller architecture for sold-state marx modulator based on FPGAPublication . Pereira, Fernando; Gomes, Luís; SANTOS REDONDO, LUIS MANUELThis paper proposes a multifunctional architecture to implement field-programmable gate array (FPGA) controllers for power converters and presents a prototype for a pulsed power generator based on a solid-state Marx topology. The massively parallel nature of reconfigurable hardware platforms provides very high processing power and fast response times allowing the implementation of many subsystems in the same device. The prototype includes the controller, a failure detection system, an interface with a safety/emergency subsystem, a graphical user interface, and a virtual oscilloscope to visualize the generated pulse waveforms, using a single FPGA. The proposed architecture employs a modular design that can be easily adapted to other power converter topologies.
- The IOPT-Flow framework pairing Petri nets and data-flows for embedded controller developmentPublication . Pereira, Fernando; Gomes, LuísThe IOPT-Flow modeling framework is a Web-based set of tools for the design of embedded and cyber-physical system controllers, comprehending a graphical editor, a simulator and automatic code generation tools. Models are designed using an hybrid formalism combining Petri nets and data-flows to specify the reactive and data-driven parts of the controllers. Model composition based on components simplify the development of complex systems, that may be assembled with the help of a library of previously designed components. The synergy of the interaction between data-flow and Petri net elements brings many advantages to the design of mixed systems that must simultaneously perform data processing operations on input signals and manage complex event driven state-machines. The resulting controllers may be implemented on software or reconfigurable hardware devices, as the code generation tools support C and VHDL. The tools are free to use and are available online http://gres.uninova.pt/iopt-flow.
- A JSON/HTTP communication protocol to support the development of distributed cyber-physical systemsPublication . Pereira, Fernando; Gomes, LuísCyber physical systems are often built using networks of components containing physical and computational resources, enabling the design of distributed applications that collect data from remote sensors and manipulate remote actuators, located on local networks or on far away locations. The communication protocol presented in this paper was designed to support the communication between components of distributed applications. In addition, it includes remote debug and monitoring capabilities, to support the detection and resolution of errors and design mistakes on nodes running on remote locations. Employing the JSON/HTTP standards, the proposed protocol is Web browser friendly, suitable for the creation of Web based applications and user interfaces, but it may be employed on most programming environments that offer libraries to support those standards. As it is based on HTTP, it can easily traverse most firewall configurations and used through proxies. Development of the proposed protocol started on the IOPTTools framework, but the current version was implemented as part of the IOPT-Flow framework, aiming the development of distributed CPS applications based on graphical formalism combining Petri nets and dataflows. Both tool frameworks are available at http://gres.uninova.pt.