Due to the increased availability of low cost network technology, the use of networks to interconnect sensors, actuators and controllers is becoming widely accepted for the implementation of feedback control systems. Such type of feedback... more
Due to the increased availability of low cost network technology, the use of networks to interconnect sensors, actuators and controllers is becoming widely accepted for the implementation of feedback control systems. Such type of feedback implementation, wherein the control loops are closed through a real-time network, are called network controlled systems (NCS). When implementing a NCS, the underlying communication network must provide a timely communication service, which must be adequate to fulfill ...
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This paper presents the application of a CAN network to the integration of sensors and actuators in an unmanned airship called HELIX, based on the architecture of distributed processing proposed by LM Pinho (2001). Initially, a study of... more
This paper presents the application of a CAN network to the integration of sensors and actuators in an unmanned airship called HELIX, based on the architecture of distributed processing proposed by LM Pinho (2001). Initially, a study of the viability of several communication networks used in vehicles (such as CAN, VAN, C2D and FIP, etc.) was accomplished. The preliminary study concluded that the behavior of CAN was better for this application when compared to other types of networks analyzed. In the present work, a ...
Research Interests:
Resumo Em Sistemas de Controle via Redes (NCS:“Networked Control Systems”) os elementos sensor, controlador e atuador trocam informações entre si através da troca de mensagens sob uma rede de comunicação, a qual gera atrasos na... more
Resumo Em Sistemas de Controle via Redes (NCS:“Networked Control Systems”) os elementos sensor, controlador e atuador trocam informações entre si através da troca de mensagens sob uma rede de comunicação, a qual gera atrasos na transmissão de mensagens que conseqüentemente introduzem atrasos de controle no processo a controlar, o que pode levar o sistema a perda de performance e instabilidade. O tempo de transmissão de mensagens depende do algoritmo de acesso ao meio de comunicação ...
Research Interests:
Due to the increased availability of low cost network technology, the use of networks to interconnect sensors, actuators and controllers is becoming widely accepted for the implementation of feedback control systems. Such type of feedback... more
Due to the increased availability of low cost network technology, the use of networks to interconnect sensors, actuators and controllers is becoming widely accepted for the implementation of feedback control systems. Such type of feedback implementation, wherein the control loops are closed through a real-time network, is called Network Controlled Systems (NCS). When implementing a NCS, the underlying communication network must provide a timely communication service, which must be the adequate to fulfil ...
Research Interests:
Research Interests:
Research Interests:
This paper presents the application of a CAN network to the integration of sensors and actuators in an unmanned airship called HELIX, based on the architecture of distributed processing proposed by LM Pinho (2001). Initially, a study of... more
This paper presents the application of a CAN network to the integration of sensors and actuators in an unmanned airship called HELIX, based on the architecture of distributed processing proposed by LM Pinho (2001). Initially, a study of the viability of several communication networks used in vehicles (such as CAN, VAN, C2D and FIP, etc.) was accomplished. The preliminary study concluded that the behavior of CAN was better for this application when compared to other types of networks analyzed. In the present work, a ...
Research Interests:
In this paper we describe a real-time industrial communication network able to support both controlrelated and multimedia traffic. The industrial communication network is based on the PROFIBUS standard, with multimedia capabilities being... more
In this paper we describe a real-time industrial communication network able to support both controlrelated and multimedia traffic. The industrial communication network is based on the PROFIBUS standard, with multimedia capabilities being provided by an adequate integration of TCP/IP protocols into the PROFIBUS stack. From the operational point of view the integration of TCP/IP into PROFIBUS is by itself a challenge, since the master-slave nature of the PROFIBUS MAC makes complex the implementation of the ...
Abstract: Wireless Sensor Networks (WSN) currently represent the best candidate to be adopted as the communication solution for the last mile connection in process control and monitoring applications in industrial environments. Most of... more
Abstract: Wireless Sensor Networks (WSN) currently represent the best candidate to be adopted as the communication solution for the last mile connection in process control and monitoring applications in industrial environments. Most of these applications have stringent dependability (reliability and availability) requirements, as a system failure may result in economic losses, put people in danger or lead to environmental damages.
ABSTRACT Due to the increased availability of low cost network technology, the use of networks to interconnect sensors, actuators and controllers is becoming widely accepted for the implementation of feedback control systems. Such type of... more
ABSTRACT Due to the increased availability of low cost network technology, the use of networks to interconnect sensors, actuators and controllers is becoming widely accepted for the implementation of feedback control systems. Such type of feedback implementation, wherein the control loops are closed through a real-time network, is called Network Controlled Systems (NCS).
Page 1. Real-Time Communication in IEEE 802.11 Wireless Mesh Networks: A Prospective Study Carlos Manuel Dias Viegas DSIE'11 - Doctoral Symposium on Informatics Engineering January 2011 Faculty of Engineering of the University of Porto... more
Page 1. Real-Time Communication in IEEE 802.11 Wireless Mesh Networks: A Prospective Study Carlos Manuel Dias Viegas DSIE'11 - Doctoral Symposium on Informatics Engineering January 2011 Faculty of Engineering of the University of Porto Page 2.
Abstract In this paper we address the ability of WorldFIP to cope with the real-time requirements of distributed computer-controlled systems (DCCS). Typical DCCS include process variables that must be transferred between network devices... more
Abstract In this paper we address the ability of WorldFIP to cope with the real-time requirements of distributed computer-controlled systems (DCCS). Typical DCCS include process variables that must be transferred between network devices both in a periodic and sporadic (aperiodic) basis. The WorldFIP protocol is designed to support both types of traffic. WorldFIP can easily guarantee the timing requirements for the periodic traffic.
Abstract In this paper, a TDMA-based mechanism is proposed for IEEE 802.11 Wireless LANs. This mechanism prioritizes real-time traffic in IEEE 802.11 networks, allowing the coexistence of standard stations with modified (real-time)... more
Abstract In this paper, a TDMA-based mechanism is proposed for IEEE 802.11 Wireless LANs. This mechanism prioritizes real-time traffic in IEEE 802.11 networks, allowing the coexistence of standard stations with modified (real-time) stations in the same network domain. The worst-case timing analysis of the TDMA-based mechanism shows that the service interval is upper-bounded, even when the communication medium is shared with timing unconstrained stations.
Abstract. Due to the increased availability of low cost network technology, the use of networks to interconnect sensors, actuators and controllers is becoming widely accepted for the implementation of feedback control systems. Such type... more
Abstract. Due to the increased availability of low cost network technology, the use of networks to interconnect sensors, actuators and controllers is becoming widely accepted for the implementation of feedback control systems. Such type of feedback implementation, wherein the control loops are closed through a real-time network, are called Network Controlled Systems (NCS).
Abstract. In this paper, a new traffic separation mechanism is proposed for IEEE 802.11 e networks. Such Traffic Separation Mechanism (TSm) allows the coexistence of CSMA default stations with real-time stations in the same network... more
Abstract. In this paper, a new traffic separation mechanism is proposed for IEEE 802.11 e networks. Such Traffic Separation Mechanism (TSm) allows the coexistence of CSMA default stations with real-time stations in the same network domain. A station implementing the proposed TSm scheme has the same operating behavior as a default IEEE 802.11 e network station, except in what concerns the evaluation of the backoff delay.
Abstract In this paper, we propose a TDMA-based communication approach to be used upon the EDCA communication mechanism defined in the IEEE 802.11 e standard. This approach allows the coexistence of realtime (RT) traffic together with... more
Abstract In this paper, we propose a TDMA-based communication approach to be used upon the EDCA communication mechanism defined in the IEEE 802.11 e standard. This approach allows the coexistence of realtime (RT) traffic together with uncontrolled (external) traffic sources. In the context of this paper, RT traffic means small sized packets generated in periodic intervals, which must be delivered before the end of the message stream period.
Resumo Neste artigo é apresentada a aplicação da margem de jitter no projeto de NCS (“Networked Control Systems”), com base no conceito de margem de jitter apresentado em (Cervin et al., 2004). Sabendo que os algoritmos de escalonamento... more
Resumo Neste artigo é apresentada a aplicação da margem de jitter no projeto de NCS (“Networked Control Systems”), com base no conceito de margem de jitter apresentado em (Cervin et al., 2004). Sabendo que os algoritmos de escalonamento de tempo real introduzem jitter de saída na malhas de controle, com base num projeto integrado de controleescalonamento, é possível através de teste de escalonabilidade otimizar a execução das tarefas de controle.
Resumo Em Sistemas de Controle via Redes (NCS:“Networked Control Systems”) os elementos sensor, controlador e atuador trocam informações entre si através da troca de mensagens sob uma rede de comunicação, a qual gera atrasos na... more
Resumo Em Sistemas de Controle via Redes (NCS:“Networked Control Systems”) os elementos sensor, controlador e atuador trocam informações entre si através da troca de mensagens sob uma rede de comunicação, a qual gera atrasos na transmissão de mensagens que conseqüentemente introduzem atrasos de controle no processo a controlar, o que pode levar o sistema a perda de performance e instabilidade.
Abstract. Deriving fault-tolerant schedulability resilience for real-time systems has been a challenge. While some approaches are based on worst-case conditions, some others are designed to a specific scheduling policy. A simulationbased... more
Abstract. Deriving fault-tolerant schedulability resilience for real-time systems has been a challenge. While some approaches are based on worst-case conditions, some others are designed to a specific scheduling policy. A simulationbased analysis has recently been proposed as an attempt to overcome such shortcomings. Its basic idea is to simulate the system in specific time windows and then infer a resilience value for the analyzed system.
Resumo. O padrao IEEE 802.15. 4 oferece uma soluçao flexıvel de comunicaç ao para redes LR-WPAN. Quando ativo, o modo com beacon habilita comunicaç ao de tempo real através da adoç ao de GTS (Guaranteed Time Slot). No entanto, este modo... more
Resumo. O padrao IEEE 802.15. 4 oferece uma soluçao flexıvel de comunicaç ao para redes LR-WPAN. Quando ativo, o modo com beacon habilita comunicaç ao de tempo real através da adoç ao de GTS (Guaranteed Time Slot). No entanto, este modo de transmissao suporta apenas que sete dispositivos da rede possam se beneficiar deste recurso em cada superquadro. Este trabalho, introduz uma nova técnica de escalonamento dinâmico de GTSs baseada no modelo de tarefas (m, k)-firm.
Abstract Wireless sensor networks may be deployed to retrieve visual information from the monitored field, enriching monitoring and control applications. Whenever a set of camera-enabled sensor nodes are deployed for time-critical... more
Abstract Wireless sensor networks may be deployed to retrieve visual information from the monitored field, enriching monitoring and control applications. Whenever a set of camera-enabled sensor nodes are deployed for time-critical monitoring, visual information as still images and video streams may need to reach the sink as soon as possible, requiring a differentiated treating of the network when compared with non-critical visual data.
Resumo Com a grande disponibilidade eo baixo custo atual da tecnologia de redes, a utilização das redes de computadores para interconectar sensores, atuadores e controladores está tornando-se amplamente aceita para a implementação de... more
Resumo Com a grande disponibilidade eo baixo custo atual da tecnologia de redes, a utilização das redes de computadores para interconectar sensores, atuadores e controladores está tornando-se amplamente aceita para a implementação de sistemas de controle realimentado. Tal tipo de implementação, na qual as malhas de controle são fechadas utilizando uma rede de comunicação de tempo real, são chamadas de Sistemas de Controle via Redes (ou NCS, para Networked Control Systems).
Resumo-Este artigo apresenta uma nova abordagem para a modelagem e controle de um sistema de Mesa-XY controlado por computador e baseado em técnicas de escalonamento de tarefas de tempo-real como principal resultado a otimização de... more
Resumo-Este artigo apresenta uma nova abordagem para a modelagem e controle de um sistema de Mesa-XY controlado por computador e baseado em técnicas de escalonamento de tarefas de tempo-real como principal resultado a otimização de recursos computacionais na execução dos algoritmos de controle. Os algoritmos de controle são executados concorrentemente em um kernel de tempo-real, o qual baseado no paradigma de sistemas de tempo-real é possível garantirmos um desempenho de controle aceitável.
Abstract:-To ensure the correct behaviour of a Networked Control System, the communication network must provide a reliable and timely communication service. The two components with the highest impact on the communication delays are the... more
Abstract:-To ensure the correct behaviour of a Networked Control System, the communication network must provide a reliable and timely communication service. The two components with the highest impact on the communication delays are the Medium Access Control (MAC) protocol and the local communication stack, therefore, the usage of an adequate communication stack is of utmost importance to guarantee the timing correctness of a feedback control application.
Abstract. WorldFIP is standardised as European Norm EN 50170-General Purpose Field Communication System. Field communication systems (fieldbuses) started to be widely used as the communication support for distributed computer-controlled... more
Abstract. WorldFIP is standardised as European Norm EN 50170-General Purpose Field Communication System. Field communication systems (fieldbuses) started to be widely used as the communication support for distributed computer-controlled systems (DCCS), and are being used in all sorts of process control and manufacturing applications within different types of industries.
Resumo. O padrao IEEE 802.15. 4 adota o protocolo CSMA/CA, o qual nao oferece suporte para mensagens com restriç oes temporais. Neste trabalho é proposta uma abordagem de provimento de qualidade de serviço para aplicaçoes de tempo real... more
Resumo. O padrao IEEE 802.15. 4 adota o protocolo CSMA/CA, o qual nao oferece suporte para mensagens com restriç oes temporais. Neste trabalho é proposta uma abordagem de provimento de qualidade de serviço para aplicaçoes de tempo real com mınimas alteraçoes ao protocolo existente. O mecanismo proposto melhora o CSMA/CA através da atribuiç ao descentralizada de prioridades baseada no modelo de tarefas (m, k)-firm. Resultados obtidos através de análises experimentais sao apresentados.
Abstract: P-NET is a multi-master fieldbus standard based on a virtual token passing scheme. In P-NET each master is allowed to transmit only one message per token visit. In the worst-case, the communication response time can be derived... more
Abstract: P-NET is a multi-master fieldbus standard based on a virtual token passing scheme. In P-NET each master is allowed to transmit only one message per token visit. In the worst-case, the communication response time can be derived considering that, in each token cycle, all stations use the token to transmit a message. In this paper, we define a more sophisticated P-NET model, which considers the actual token utilisation.
Abstract In recent years, the FlexRay communication protocol has been promoted as a de facto standard for in-vehicular communications. In the FlexRay protocol, the communication timeline is organized as a sequence of four segments,... more
Abstract In recent years, the FlexRay communication protocol has been promoted as a de facto standard for in-vehicular communications. In the FlexRay protocol, the communication timeline is organized as a sequence of four segments, whereas the static segment defines a set of slots specifically designed for the transmission of synchronous messages.
Abstract The evolvement of Ethernet in factory automation and test & measurement applications generated the need for high-accuracy clock synchronization. While factory communication can normally fulfil application requirements based on an... more
Abstract The evolvement of Ethernet in factory automation and test & measurement applications generated the need for high-accuracy clock synchronization. While factory communication can normally fulfil application requirements based on an average accuracy in the range of microseconds, test & measurement and several other applications (eg wireless position determination) seek for ultimate performance, meaning nanoseconds at most.
Abstract: Wireless Local Area Networks (WLAN) has attracted significant interest to support real-time communication. The most promising solution was recently published as IEEE 802.11 e, which provide traffic differentiation. However, that... more
Abstract: Wireless Local Area Networks (WLAN) has attracted significant interest to support real-time communication. The most promising solution was recently published as IEEE 802.11 e, which provide traffic differentiation. However, that solution still has an inadequate behavior to support real-time applications. In this paper, we propose a new traffic separation mechanism for IEEE 802.11 e networks.
Abstract In this paper, we present some of the fault tolerance management mechanisms being implemented in the Multi-μ-architecture, namely its support for replica non-determinism. In this architecture, fault tolerance is achieved by... more
Abstract In this paper, we present some of the fault tolerance management mechanisms being implemented in the Multi-μ-architecture, namely its support for replica non-determinism. In this architecture, fault tolerance is achieved by node active replication, with software based replica management and fault tolerance transparent algorithms.
Abstract. Agents paradigms are very popular due to their flexibility, modularity and general applicability to a very wide range of problems. Nowadays, the majority of the agents used in computer networks are passive agents, ie, the agent... more
Abstract. Agents paradigms are very popular due to their flexibility, modularity and general applicability to a very wide range of problems. Nowadays, the majority of the agents used in computer networks are passive agents, ie, the agent has no autonomy, and there is no participation in decision-making actions. In this paper, we present a methodology for agent's development with the employment of artificial intelligence techniques. The methodology has been applied to the baselines development for proactive network management.
Abstract The timing behavior of the EDCAmechanism defined in the IEEE 802.11 e standard is analyzed. More specifically, the target of this paper is to evaluate the limitations of the highest priority level of the EDCA mechanism (voice... more
Abstract The timing behavior of the EDCAmechanism defined in the IEEE 802.11 e standard is analyzed. More specifically, the target of this paper is to evaluate the limitations of the highest priority level of the EDCA mechanism (voice category) when supporting real-time (RT) communication. By RT communication, we mean small-sized packets generated in periodic intervals that must be delivered before the end of the message stream period. Otherwise, the message is considered to be delayed and a deadline loss occurs.
This paper proposes an environment intended for the development of fault-tolerant real-time Ada 95 applications conforming to the Ravenscar profile. This environment is based on the transparent replication of application components, and... more
This paper proposes an environment intended for the development of fault-tolerant real-time Ada 95 applications conforming to the Ravenscar profile. This environment is based on the transparent replication of application components, and it provides a set of generic task interaction objects, which are used as the basic building blocks of the supported applications.
Abstract The IEEE 802.11 s draft standard defines a mesh network in which frame delivery is done by forwarding the frame through nodes, called Mesh Points (MPs). To make this possible, it specifies two routing protocols: HWMP and RA-OLSR.... more
Abstract The IEEE 802.11 s draft standard defines a mesh network in which frame delivery is done by forwarding the frame through nodes, called Mesh Points (MPs). To make this possible, it specifies two routing protocols: HWMP and RA-OLSR. Both protocols suffer from scalability issues caused by the use of broadcast messages for discovery and update of routes. In this work, we propose a new routing protocol, the DHT-based Cluster Routing Protocol (DCRP), that improves the scalability of 802.11 s networks.