2014
Autores
De Sousa, M;
Publicação
19th IEEE International Conference on Emerging Technologies and Factory Automation, ETFA 2014
Abstract
Being distributed in nature, IEC 61499 industrial control applications are subject to partial failures. Building applications that are tolerant of these failures (i.e. a fault-tolerant application) may be achieved through the use of replication. In this paper we present a framework to support replicated IEC 61499 applications, and study how replica determinism may be achieved in this framework. © 2014 IEEE.
2017
Autores
Homay, A; de Sousa, M; Almeida, L;
Publicação
2017 IEEE 15TH INTERNATIONAL CONFERENCE ON INDUSTRIAL INFORMATICS (INDIN)
Abstract
An emerging trend in industry 4.0 is to use wireless communication infrastructure and mesh networks in applications requiring high reliability and safety. Although not a typical industrial production process, railway vehicular networks are also an industrial application which come with stringent reliability and safety requirements. Current research is focusing on using vehicular networks as an enabling technology to actively control the separation between two consecutive vehicles, enforcing a safe distance which is nevertheless much shorter than currently used to maintain vehicle separation. In this respect, we analyze a hopping strategy for Time-Slotted Channel-Hopping (TSCH), which was introduced in the IEEE 802.15.4e amendment with a view of improving the reliability of IEEE 802.15.4 networks. We define a probability framework to estimate the chance of successful hopping assuming two previously merged vehicles, and we design a zero-sum game and propose a payoff function to always place communicating nodes in a Nash equilibrium by choosing whether to hop or not, and therefore maximizing the communication throughput by mitigating jamming signals.
2010
Autores
Marau, R; Almeida, L; Sousa, M; Pedreiras, P;
Publicação
2010 IEEE CONFERENCE ON EMERGING TECHNOLOGIES AND FACTORY AUTOMATION (ETFA)
Abstract
The middleware is an important software component when designing an application, facilitating the development and deployment of the applications. In the case of Distributed Embedded Systems (DES), the middleware should provide basic functionalities to abstract the complexity that results from network distribution, namely data consistency, events synchronization and resource management. Often DES applications exhibit real-time requirements and have to deal with dynamic environments that present evolving requirements. While some middleware architectures have been proposed to address resource provisioning and QoS management, none of those middle-wares supports dynamic resource reconfiguration while providing real-time guarantees. This paper proposes a middleware layer, based on the services provided by a flexible real-time communication protocol, addressing distribution abstraction, dynamic reconfiguration and dynamic QoS management under real-time constraints.
2007
Autores
Tisserant, E; Bessard, L; de Sousa, M;
Publicação
2007 5TH IEEE INTERNATIONAL CONFERENCE ON INDUSTRIAL INFORMATICS, VOLS 1-3
Abstract
The IEC 61131-3 standard defines a common framework for programming PLCs (Programmable Logic Controllers), which includes the complete definition of four programming languages and a state machine definition language. Industrial PLC vendors are slowly offering support for this standard, however small inconsistencies remain between their implementations, transferring programs between vendors is almost impossible due to different rile formats, and licenses are generally too expensive to allow students do install these commercial solutions on their own computers. To this end, the authors have developed an Integrated Development Environment (IDE) for the IEC 61131-3 framework, which is being offered to the general public under the GNU Public License (GPL). The IDE consists of a Graphical User Interface (GUI) and a backend compiler. Using the GUI the user may develop programs in any of the four programming languages, as well as the state machine definition language. The backend compiler is used to convert these programs into equivalent C++ programs which may later be compiled and executed on various platforms.
2000
Autores
De Sousa, M; Carvalho, A;
Publicação
Proceedings - DOA 2000: International Symposium on Distributed Objects and Applications
Abstract
RT CORBA has been specified with the intention of supporting real-time (RT) distributed applications using diverse scheduling, resource access and synchronisation protocols. This work analyses how two specific synchronisation protocols may be implemented over RT CORBA, and concludes that it is not possible if the spirit of the RT CORBA specification is to be followed, and unless current operating system services are augmented. We propose several changes to make this mapping possible. © 2000 IEEE.
2003
Autores
De Sousa, M; Carvalho, A;
Publicação
IEEE International Conference on Emerging Technologies and Factory Automation, ETFA
Abstract
We have implemented an IEC 61131-3 IL (Instruction List) and ST (Structured Text) compiler that will be part of an open source PLC. In doing so, several issues were found regarding the specification of the IL and ST languages, produced by the IEC (International Electrotechnical Commission ) standards body. The uncovered issues are discussed in this paper, and some changes to the standard are proposed. The architecture used in the compiler implementation is also outlined in the paper. © 2003 IEEE.
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