Anikó Costa

The Input-Output Place-Transition Petri Net Class and Associated Tools

Petri nets are a well-known formalism widely used in different application areas. Yet, the lack of adequate tools that can be integrated within engineering development frameworks are one major drawback. This paper identifies and justifies the characteristics of one class of Petri nets targeted for the modelling of automation systems and (networked) embedded systems, named as input-output Petri net (IOPT), and its representation using the Petri net markup language (PNML). The paper also presents a set of associated tools under development. This Petri net class, defined on top of the well-known place-transition Petri nets, is the common link across a set of tools under development, including a graphical editor, a state-space analyser for the verification of properties, conflict resolution through automatic arbiter generation, automatic code generators, simulator, among others. In this sense, the main goal of the proposed Petri net class and associated tools is to support the entire system development flow, from specification to implementation.

From Petri net models to VHDL implementation of digital controllers

Modeling of discrete-event systems using Petri net models is well-studied. Also, their usage for specification of digital controllers is widely used. Yet, it is recognized that we have a lack of tools when facing support for the implementation of these models, namely for automatic code generation. The paper briefly presents the FORDESIGN project that aims to develop a set of tools to contribute for filling this gap within automation systems and (networked) embedded systems development. The set of tools is based on a Petri net class, named as Input-Output Petri Net (IOPT), and its representation using the Petri Net Markup Language (PNML). The paper presents some rules used by an automatic code generator able to produce VHDL code starting with the PNML representation of the Petri net model.

Remote laboratory support for an introductory microprocessor course

Introductory microprocessor design courses can benefit from the usage of laboratory assignments, leading, normally, to high rates of laboratory space and time occupation. In this paper, a remote laboratory is proposed in order to alleviate the laboratorys physical occupation. An 8031 microcontroller based set-up was used to support a set of experiments. Local and remote accesses to the experiments are possible, supported by the LabView environment, and complemented by a specific virtual workbench adaptor to emulate user presence.

From use cases to system implementation: statechart based co-design

This paper proposes a methodology for embedded systems co-design, based on statechart models. The process starts with grabbing the system functionalities through use cases. A set of procedures addressing the implementation of statechart models is presented. The main goal of this set of procedures is to lift the structuring mechanisms presented in statecharts to the top level. In this sense, the complexity of statechart implementation will be similar to the complexity of communicating concurrent state machines and the platforms selected to support implementation will not need to have specific capabilities to directly support the structuring mechanisms of Harels statecharts. As a consequence, full direct implementation of statecharts is possible considering different types of implementation platforms, ranging from hardware-centric or software-centric to hardware-software partitioning through codesign techniques.

Petri nets tools framework supporting FPGA-based controller implementations

This paper presents a set of tools having embedded systems co-design as the main target area of application and Petri nets as the underlying modeling formalism. The presented tools have been developed within the framework of the R&D FORDESIGN project, which will be briefly presented along with the proposed development methodology. The Petri net model, which is defined on top of the well-known place-transition Petri nets class, and represented in compliance with the PNML format, is the common link across the set of tools already developed (beta versions). These include a graphical editor, automatic code generators for different target languages (namely C and VHDL), tools for model composition and model decomposition (to support the usage of co-design techniques), and a configuration tool (where reconfigurable platforms, like FPGAs, and microcontroller architectures are considered as implementation platforms). The usage of some of the developed tools is briefly presented using an automation system example, in order to obtain specifications for a set of distributed controllers, and deployment into an FPGA-based implementation platform.

Ecore representation for extending PNML for Input-Output Place-Transition nets

This paper presents a metamodel for the Input-Output Place-Transition nets (IOPT nets), a Petri net class targeted at controllers modeling. The proposed metamodel reuses many of the elements of the Petri Net Markup Language (PNML) metamodel, such as places, transitions, and arcs; it extends the PNML metamodel for Place/Transition nets to comprise concepts inherent to IOPT nets. The IOPT nets metamodel is described in Ecore format, putting IOPT nets in the puzzle of MDA artifacts taking benefit from the MDA infrastructure.

Architecture for remote laboratories based on REST web services

In this paper, a new architecture for remote laboratories based on REST (Representational State Transfer) web services is proposed. The proposed platform use languages such as HTML, AJAX (asynchronous Javascript and XML) and Labview. A web browser is the client interface and on the server side runs an application based on Labview 8.6 with REST web resources. The main contributions are: a) the proposed architecture; b) a “thin client“ based on a browser requiring a low bandwidth. Experimental tests, using an analog process simulator, were done and the obtained results show a good performance.

Petri net Splitting Operation within Embedded Systems Co-design

As system complexity increases, the role of Model Based Development is more and more important. Several modeling formalisms are widely used when considering the area of hardware-software co-design of embedded systems. The goal of the work presented in this paper is to contribute for the usage of Petri nets as the system-level specification language. Techniques for system model partitioning into components are a major concern within co-design methodologies. This paper proposes a net operation, called net splitting, able to decompose a Petri net model into Petri net sub-models using synchronous communication channels. The operation is based on the definition of a valid cutting set. Specific rules are presented in order to obtain the sub-models from the initial one. The generated sub-models are associated with components to be executed concurrently, allowing a distributed execution of the initial model. On the other hand, at the implementation level, it is necessary to accommodate a severe deviation on synchronous communication channel execution semantics (as far as the components are in execution in different controllers and zero time delay is not possible to obtain). For some specific situations, initial model properties are not preserved considering execution of components obtained after net splitting operation. Although, it is possible to anticipate the impact of using specific communication channels models at the implementation level. For that end, a second step on property verification is needed in order to validate a specific partitioning solution. An illustrative example applying the referred mechanisms is presented.

Extending input-output place-transition Petri nets for distributed controller systems development

Petri nets have been widely used in the design of embedded controllers, namely in electronic hardware and computing platforms design, as well as within automation application areas. This paper presents updated characteristics of one class of Petri nets, named Input-Output Place-Transition Petri nets (IOPT nets), extended to support networked embedded controllers design and globally-asynchronous locally-synchronous (GALS) systems modeling, together with its associated metamodel and execution semantics. The proposed meta-model is compliant with the Petri Net Markup Language (PNML) metamodel, augmented with the descriptions for inputs and outputs, as well as for time domains and communication channels. The meta-model is described using UML class diagrams and has an equivalent Ecore meta-model that positioning IOPT nets within the Eclipse Modeling Framework (EMF).

On lifting of statechart structuring mechanisms

We propose a set of procedures addressing the implementation of statechart models. The main goal of this set of procedures is to lift the structuring mechanisms presented in statecharts to the top level. In this sense, the complexity of statechart implementation will be similar to the complexity of communicating concurrent state machines and the platforms selected to support implementation will not need to have specific capabilities to directly support the structuring mechanisms of Harels statecharts. The framework is the design of embedded systems (in the sense of reactive realtime systems) and automation applications, either industrial automation or building automation, either the emphasis is on system, hardware or software levels, using or not codesign techniques. An application focused on hardware implementation using VHDL as implementation language is used as an example.