15 research outputs found
Industrial Fieldbus Improvements in Power Distribution and Conducted Noise Immunity With No Extra Costs
Industrial distributed control continues the move
toward networks at all levels. At lower levels, control networks
provide flexibility, reliability, and low cost, although perhaps the
simplest but most important advantage is the reduced volume
of wiring. Powered fieldbuses offer particular notable benefits in
system wiring simplification. Nevertheless, very few papers are
dealing with the potentials and limitations in power distribution
through the bus cable. Only a few of the existent fieldbus standards
consider this possibility but often simply as an option without
enough technical specifications. In fact, nobody talks about it, but
power distribution through the bus and conducted noise disturbances
are strongly related. This paper points out and analyzes
these limitations and proposes a new low-cost fieldbus physical
layer that enlarges power distribution capability of the bus and
improves system robustness. We show an industrial application
on water desalination plants and the very good results obtained
owing to the fieldbus. Finally, we present electromagnetic compatibility
test results that verify improvements against electrical fast
transients on the sensor/actuator connection side as disturbances
usually encountered in harsh-environment industrial applications
Wireless model-based predictive networked control system over cooperative wireless network
Owing to their distributed architecture, networked control systems (NCSs) are proven to be feasible in scenarios where a spatially distributed feedback control system is required. Traditionally, such NCSs operate over real-time wired networks. Recently, in order to achieve the utmost flexibility, scalability, ease of deployment, and maintainability, wireless networks such as IEEE 802.11 wireless local area networks (LANs) are being preferred over dedicated wired networks. However, conventional NCSs with event-triggered controllers and actuators cannot operate over such general purpose wireless networks since the stability of the system is compromised due to unbounded delays and unpredictable packet losses that are typical in the wireless medium. Approaching the wireless networked control problem from two perspectives, this work introduces a practical wireless NCS and an implementation of a cooperative medium access control protocol that work jointly to achieve decent control under severe impairments, such as unbounded delay, bursts of packet loss and ambient wireless traffic. The proposed system is evaluated on a dedicated test platform under numerous scenarios and significant performance gains are observed, making cooperative communications a strong candidate for improving the reliability of industrial wireless networks
Power conversion and signal transmission integration method based on dual modulation of DC-DC converters
For the development of communication systems such as Internet of Things, integrating communication with power supplies is an attractive solution to reduce supply cost. This paper presents a novel method of power/signal dual modulation (PSDM), by which signal transmission is integrated with power conversion. This method takes advantage of the intrinsic ripple initiated in switch mode power supplies as signal carriers, by which cost-effective communications can be realized. The principles of PSDM are discussed, and two basic dual modulation methods (specifically PWM/FSK and PWM/PSK) are concluded. The key points of designing a PWM/FSK system, including topology selection, carrier shape, and carrier frequency, are discussed to provide theoretical guidelines. A practical signal modulation-demodulation method is given, and a prototype system provides experimental results to verify the effectiveness of the proposed solution
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A service orientated architecture and wireless sensor network approach applied to the measurement and visualisation of a micro injection moulding process. Design, development and testing of an ESB based micro injection moulding platform using Google Gadgets and business processes for the integration of disparate hardware systems on the factory shop floor
Factory shop floors of the future will see a significant increase in interconnected devices for monitoring and control. However, if a Service Orientated Architecture (SOA) is implemented on all such devices then this will result in a large number of permutations of services and composite services. These services combined with other business level components can pose a huge challenge to manage as it is often difficult to keep an overview of all the devices, equipment and services. This thesis proposes an SOA based novel assimilation architecture for integrating disparate industrial hardware based processes and business processes of an enterprise in particular the plastics machinery environment. The key benefits of the proposed architecture are the reduction of complexity when integrating disparate hardware platforms; managing the associated services as well as allowing the Micro Injection Moulding (µIM) process to be monitored on the web through service and data integration. An Enterprise Service Bus (ESB) based middleware layer integrates the Wireless Sensor Network (WSN) based environmental and simulated machine process systems with frontend Google Gadgets (GGs) based web visualisation applications. A business process framework is proposed to manage and orchestrate the resulting services from the architecture.
Results from the analysis of the WSN kits in terms of their usability and reliability showed that the Jennic WSN was easy to setup and had a reliable communication link in the polymer industrial environment with the PER being below 0.5%. The prototype Jennic WSN based µIM process monitoring system had limitations when monitoring high-resolution machine data, therefore a novel hybrid integration architecture was proposed. The assimilation architecture was implemented on a distributed server based test bed. Results from test scenarios showed that the architecture was highly scalable and could potentially allow a large number of disparate sensor based hardware systems and services to be hosted, managed, visualised and linked to form a cohesive business process
Comunicações sem-fios de tempo-real para ambientes abertos
Doutoramento em Engenharia InformáticaWireless communication technologies have become widely adopted, appearing
in heterogeneous applications ranging from tracking victims, responders and
equipments in disaster scenarios to machine health monitoring in networked
manufacturing systems. Very often, applications demand a strictly bounded
timing response, which, in distributed systems, is generally highly dependent
on the performance of the underlying communication technology. These
systems are said to have real-time timeliness requirements since data
communication must be conducted within predefined temporal bounds, whose
unfulfillment may compromise the correct behavior of the system and cause
economic losses or endanger human lives.
The potential adoption of wireless technologies for an increasingly broad range
of application scenarios has made the operational requirements more complex
and heterogeneous than before for wired technologies. On par with this trend,
there is an increasing demand for the provision of cost-effective distributed
systems with improved deployment, maintenance and adaptation features.
These systems tend to require operational flexibility, which can only be ensured
if the underlying communication technology provides both time and event
triggered data transmission services while supporting on-line, on-the-fly
parameter modification.
Generally, wireless enabled applications have deployment requirements that
can only be addressed through the use of batteries and/or energy harvesting
mechanisms for power supply. These applications usually have stringent
autonomy requirements and demand a small form factor, which hinders the use
of large batteries. As the communication support may represent a significant
part of the energy requirements of a station, the use of power-hungry
technologies is not adequate. Hence, in such applications, low-range
technologies have been widely adopted. In fact, although low range
technologies provide smaller data rates, they spend just a fraction of the energy
of their higher-power counterparts.
The timeliness requirements of data communications, in general, can be met by
ensuring the availability of the medium for any station initiating a transmission.
In controlled (close) environments this can be guaranteed, as there is a strict
regulation of which stations are installed in the area and for which purpose.
Nevertheless, in open environments, this is hard to control because no a priori
abstract
knowledge is available of which stations and technologies may contend for the
medium at any given instant. Hence, the support of wireless real-time
communications in unmanaged scenarios is a highly challenging task.
Wireless low-power technologies have been the focus of a large research
effort, for example, in the Wireless Sensor Network domain. Although bringing
extended autonomy to battery powered stations, such technologies are known
to be negatively influenced by similar technologies contending for the medium
and, especially, by technologies using higher power transmissions over the
same frequency bands. A frequency band that is becoming increasingly
crowded with competing technologies is the 2.4 GHz Industrial, Scientific and
Medical band, encompassing, for example, Bluetooth and ZigBee, two lowpower
communication standards which are the base of several real-time
protocols. Although these technologies employ mechanisms to improve their
coexistence, they are still vulnerable to transmissions from uncoordinated
stations with similar technologies or to higher power technologies such as Wi-
Fi, which hinders the support of wireless dependable real-time communications
in open environments.
The Wireless Flexible Time-Triggered Protocol (WFTT) is a master/multi-slave
protocol that builds on the flexibility and timeliness provided by the FTT
paradigm and on the deterministic medium capture and maintenance provided
by the bandjacking technique. This dissertation presents the WFTT protocol
and argues that it allows supporting wireless real-time communication services
with high dependability requirements in open environments where multiple
contention-based technologies may dispute the medium access. Besides, it
claims that it is feasible to provide flexible and timely wireless communications
at the same time in open environments. The WFTT protocol was inspired on
the FTT paradigm, from which higher layer services such as, for example,
admission control has been ported. After realizing that bandjacking was an
effective technique to ensure the medium access and maintenance in open
environments crowded with contention-based communication technologies, it
was recognized that the mechanism could be used to devise a wireless
medium access protocol that could bring the features offered by the FTT
paradigm to the wireless domain. The performance of the WFTT protocol is
reported in this dissertation with a description of the implemented devices, the
test-bed and a discussion of the obtained results.As tecnologias de comunicação sem fios tornaram-se amplamente adoptadas,
surgindo em aplicações heterógeneas que vão desde a localização de vítimas,
pessoal médico e equipamentos em cenários de desastre à monitorização da
condição física de máquinas em ambientes industrials. Muito frequentemente,
as aplicações exigem uma resposta limitada no tempo que, geralmente, em
sistemas distribuídos, é substancialmente dependente do desempenho da
tecnologia de comunicação utilizada. Estes sistemas tendem a possuir
requisitos de tempo-real uma vez que a comunicação de dados tem de ser
conduzida dentro de limites temporais pré-definidos que, quando não
cumpridos, podem comprometer o correcto funcionamento do sistema e
resultar em perdas económicas ou colocar em risco vidas humanas.
A potencial adopção de tecnologias sem-fios para um crescente número de
cenários traduz-se num aumento da complexidade e heterogeneidade dos
requisitos operacionais relativamente às tecnologias cabladas. A acompanhar
esta tendência verifica-se uma crescente procura de sistemas distribuídos,
caracterizados quer por uma boa relação custo-eficácia, quer pela simplicidade
de instalação, manutenção e adaptação. Ao mesmo tempo, estes sistemas
tendem a requerer flexibilidade operacional, que apenas pode ser assegurada
se a tecnlogia de comunicação empregue supportar transmissões de dados
dispoletadas quer por eventos (event-triggered), quer por tempo (timetriggered)
e se, ao mesmo tempo, em funcionamento, permitir a alteração dos
parâmetros de comunicação correspondentes.
Frequentemente, as aplicações com comunicações sem fios caracterizam-se
por exigências de instalação que apenas podem ser endereçadas usando
alimentação através de baterias e/ou mecanismos de recolha de energia do
ambiente envolvente. Estas aplicações têm tipicamente requisitos exigentes de
autonomia e de tamanho, impedindo o recurso a baterias de grande dimensão.
Dado que o suporte de comunicações pode representar uma parte significativa
dos requisitos de energia da estação, o uso de tecnologias de comunicação de
elevado consumo não é adequado. Desta forma, nestas aplicações, as
tecnologias de comunicação de curto-alcance tornaram-se amplamente
adoptadas uma vez que, apesar de se caracterizarem por taxas de
transmissão inferiores, consomem apenas uma fracção da energia das
tecnologias de maior alcance.
resumo
Em geral, os requisitos de pontualidade da comunicação de dados podem ser
cumpridos através da garantia da disponibilidade do meio no instante em que
qualquer estação inicie uma transmissão. Em ambientes controlados esta
disponibilidade pode ser garantida, na medida em que existe um controlo de
quais as estações que foram instaladas na área e qual a sua função.
Contrariamente, em ambientes abertos, tal controlo é difícil de garantir uma
vez que não existe conhecimento a priori de que estações ou tecnologias
podem competir pelo meio, tornando o suporte de comunicações de temporeal
um desafio difícil de implementar em cenários com estações de
comunicação não controladas.
As comunicações de baixo consumo têm sido o foco de um esforço de
investigação bastante amplo, por exemplo, no domínio das redes de sensores
sem fios. Embora possam permitir uma maior autonomia a estações baseadas
em baterias, estas tecnologias são reconhecidas como sendo negativamente
influenciadas por tecnologias semelhantes competindo pelo mesmo meio e,
em particular, por tecnologias que utilizem níveis de potência de transmissão
mais elevados em bandas de frequências comuns. De forma cada vez mais
acentuada, a banda industrial, científica e médica (ISM) dos 2.4 GHz tem-se
tornado mais saturada com tecnologias que competem entre si pelo acesso ao
meio tais como, por exemplo, Bluetooth e ZigBee, dois padrões de
comunicação que são a base de vários protocolos de tempo-real. Apesar
destas tecnologias aplicarem mecanismos para melhorar a sua coexistência,
são vulneráveis a transmissões de estações não controladas que usem as
mesmas tecnologias ou que usem tecnologias com níveis de potência de
transmissão mais elevados, impedindo, desta forma, o suporte de
comunicações de tempo-real fiáveis em ambientes abertos.
O protocolo de comunicação sem fios flexível disparado por tempo (WFTT) é
baseado numa arquitectura mestre/múltiplo escravo alavancado na
flexibilidade e pontualidade promovidas pelo paradigma FTT e na captura e
manutenção determinística do meio suportadas pela técnica de bandjacking
(captura de banda). Esta tese apresenta o protocolo WFTT e argumenta que
este permite suportar serviços de comunicação de tempo-real com requisitos
elevados de fiabilidade em ambientes abertos onde várias tecnologias de
comunicação baseadas em contenção disputam o acesso ao meio. Adicionalmente, esta tese reivindica que é possível suportar comunicações
sem-fios simultaneamente flexíveis e pontuais em ambientes abertos. O
protocolo WFTT foi inspirado no paradigma FTT, do qual importa os serviços
de alto nível como, por exemplo, o controlo de admissão. Após a observação
da eficácia da técnica de bandjacking em assegurar o acesso ao meio e a
correspondente manutenção, foi reconhecida a possibilidade de utilização
deste mecanismo para o desenvolvimento de um protocolo de acesso ao meio,
capaz de oferecer as funcionalidades do paradigma FTT em meios de
comunicação sem-fios. O desempenho do protocolo WFTT é reportado nesta
tese com uma descrição dos dispositivos implementados, da bancada de
ensaios desenvolvida e dos resultados obtidos
A survey of cognitive radio handoff schemes, challenges and issues for industrial wireless sensor networks (CR-IWSN)
Industrial wireless sensor network (IWSN) applications are mostly time-bound, mission-critical and highly delay sensitive applications therefore IWSN defines strict, stringent and unique QoS requirements such as timeliness, reliability and availability. In IWSN, unlike other sensor networks, late arrival of packets or delay or disruption to an on-going communication are considered as critical failure. Also, because IWSN is deployed in the overcrowded industrial, scientific, and medical (ISM) band it is difficult to meet this unique QoS requirements due to stiff competition for bandwidth from other technologies operating in ISM band resulting in scarcity of spectrum for reliable communication and/or disruption of ongoing communication. However, cognitive radio (CR) provides more spectral opportunities through opportunistic-use of unused licensed spectrum while ensuring minimal interference to licensed users. Similarly, spectrum handoff, which is a new type of handoff in cognitive radio, has the potential to offer increase bandwidth, reliable, smooth and interference-free communication for IWSNs through opportunistic-use of spectrum, minimal switching-delays, and efficient target channel selection strategies as well as effective link recovery maintenance. As a result, a new paradigm known as cognitive radio industrial wireless sensor network (CR-IWSN) has become the interest of recent research efforts. In this paper, we highlight and discuss important QoS requirements of IWSN as well as efforts of existing IWSN standards to address the challenges. We discuss the potential and how cognitive radio and spectrum handoff can be useful in the attempt to provide real-time reliable and smooth communication for IWSNs.The Council for Scientific and Industrial Research (CSIR), South Africa [ICT: Meraka].http://www.elsevier.com/locate/jnca2018-11-01hj2017Electrical, Electronic and Computer Engineerin
Design implementation and analysis of wireless model based predictive networked control system over cooperative wireless network
Owing to their distributed architecture, networked control systems are proven to be feasible in scenarios where a spatially distributed control system is required. Traditionally, such networked control systems operate over real-time wired networks over which sensors, controllers and actuators interact with each other. Recently, in order to achieve the utmost flexibility, scalability, ease of deployment and maintainability, wireless networks such as IEEE 802.11 LANs are being preferred over dedicated wired networks. However, basic networked control systems cannot operate over such general purpose wireless networks since the stability of the system is compromised due to unbounded delays and unpredictable packet losses that are typical in the wireless medium. Approaching the wireless networked control problem from two perspectives, this thesis proposes a novel wireless networked control system and a realistic cooperative medium access control protocol implementation that work jointly to achieve decent control even under unbounded delay, bursts of packet loss and ambient wireless traffic. The proposed system is implemented and thoroughly evaluated on a dedicated test platform under numerous scenarios and is shown to be operational under bursts of packet loss and ambient wireless traffic levels which are intolerable for basic networked control systems while not being hindered by restraining assumptions of existing methods