• 제어로봇시스템학회논문지
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• 제16권4호
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• pp.403-410
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• 2010

The switched Ethernet has many features for real-time communications such as providing traffic isolation, large bandwidth, and full-duplex links, and so on. The switched Ethernet, however, cannot guarantee the timely delivery of a real-time message because message delay increases when collisions occurs at the output ports and message loss can even occur due to the overflow at the output buffer. Recently, many research efforts have been done to use the switched Ethernet as an industrial control network. In the industrial control network, sensors periodically sense the physical environment and transmit the sensed data to an actuator, and the periodic messages from sensors to actuators have typically real-time requirements such that those messages must be transmitted within their deadlines. This paper first suggests a feasible condition for EDF (Earliest Deadline First)-based scheduling of periodic messages on a synchronized switched Ethernet and a message scheduling algorithm which satisfies the proposed feasible condition. Pedreiras, et al. [10] suggested a feasible condition for message scheduling on the Ethernet (shared media Ethernet), but there has been no research result on the scheduling condition on the switched Ethernet until now. We compared the real-time message scheduling capacity between the Ethernet and the switched Ethernet by simulation. The simulation result shows that the message scheduling capacity of the Ethernet has almost remained constant as the number of nodes on the network increases, but, in the case of the switched Ethernet, the message scheduling capacity has increased linearly according to the number of nodes on the network.

• 제어로봇시스템학회논문지
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• 제9권1호
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• pp.90-98
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• 2003

The real-time industrial network, often referred to as fieldbus, is an important element for building automated manufacturing systems. Thus, in order to satisfy the real-time requirements of field devices, numerous fieldbus protocols have been announced. But the application of fieldbus has been limited due to the high cost of hardware and the difficulty in interfacing with multi-vendor products. Therefore, as an alternative to fieldbus, the computer network technology, especially Ethernet (IEEE 802.3), is being adapted to the industrial environment. However, the crucial technical obstacle for Ethernet is its non-deterministic behavior that makes it inadequate for industrial applications where real-time data have to be delivered within a certain time limit. Recently, the development of switched Ethernet shows a very promising prospect for industrial application due to the elimination of uncertainties in the network operation resulting in much improved performance. This paper focuses on the application of the switched Ethernet for industrial communications. More specifically, this paper presents an analytical and experimental performance evaluation of the switched Ethernet and a case study about networked control system.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.491-494
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• 2002

The real-time industrial network often referred to as fieldbus, is an important element for building automated manufacturing systems. Thus, in order to satisfy the real-time requirements of field devices such as sensors, actuators, and controllers. numerous standard organizations and vendors have developed various fieldbus protocols such as Profibus, WorldFIP and Foundation Fieldbus. However, the application of fieldbus has been limited due to the high cost of hardware and the difficulty in interfacing with multi-vendor products. In order to solve these problems, the computer network technology, especially Ethernet (IEEE 802.3), is being adopted lo the industrial environment. The crucial technical obstacle for Ethernet is that its non-deterministic behavior makes it inadequate for industrial applications where real-time data such as control command and alarm signal hale to be delivered within a certain time limit. Recently, the development of switched Ethernet shows a very promising prospect for industrial application due to the elimination of uncertainties in the network operation resulting in much improved performance. This paper focuses on the application of the switched Ethernet for industrial comm unications.

• 제어로봇시스템학회논문지
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• 제10권8호
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• pp.718-725
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• 2004

The real-time industrial network, often referred to as fieldbus, is an important element for intelligent manufacturing systems. Thus, in order to satisfy the real-time requirements of field devices, numerous fieldbus protocols have been announced. But, the application of fieldbus has been limited due to the high cost of hardware and the difficulty in interfacing with multi-vendor products. Therefore, as an alternative to fieldbus, the computer network technology, especially Ethernet (IEEE 802.3), is being adapted to the industrial environment. However, the crucial technical obstacle for Ethernet is its non-deterministic behavior that makes it inadequate for industrial applications where real-time data have to be delivered within a certain time limit. Recently, the development of switched Ethernet shows a very promising prospect for industrial application due to the elimination of uncertainties in the network operation resulting in much improved performance. This paper focuses on the application of the switched Ethernet with cascade structure for industrial communications. More specifically, this paper presents an analytical performance evaluation of switched Ethernet with cascade structure, and a case study about networked control system.

• 전기학회논문지
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• 제59권10호
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• pp.1923-1928
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• 2010

The IEC 61850 protocol proposed for the interoperability between IEDs(intelligent electronic devices) adopts the prioritized switched ethernet as its communication channel because substation bus is utilized to exchange both real-time and non real-time messages. The prioritized switched ethernet uses IEEE 802.1Q/p QoS(Quality of Service) in addition to IEEE 802.3 ethernet to enhance the real-time characteristics. However, IEEE 802.1Q/p QoS has priority-blocking problem that occurs when higher-priority frame transmission request during lower-priority frame transmission. To resolve this problem, this paper proposes P(Preemptive)-Ethernet. P-Ethernet uses the modified IEEE 802.1Q/p frame format and new priority preemption mechanism. This paper also implements P-Ethernet controller using FPGA (Virtex-4) and MicroBlaze processor. From the implementation results, P-Ethernet controller shows a improved latency and jitter of transmission period compare to the normal ethernet controller.

• 제어로봇시스템학회논문지
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• 제12권12호
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• pp.1241-1248
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• 2006

In high reliability systems for industrial network such as railway signal system, fieldbus protocols have been known to satisfy the real-time and fault tolerant requirements. But, the application of fieldbus has been limited due to the high cost of hardware and software, and the difficulty in interfacing with multi-vendor products. Therefore, as an alternative to fieldbus, the computer network technology, especially Ethernet(IEEE 802.3), is being adapted to the industrial network. In this paper, we propose a switched Ethernet based railway signal system because of its very promising prospect for industrial application due to the elimination of uncertainties in the network operation. In addition, we propose the redundancy architecture for the reliability of network components. More specifically, this paper presents an analytical performance evaluation of switched Ethernet for railway signal system, and shows experimental evaluation of redundancy architecture.

• 정보처리학회논문지C
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• 제11C권1호
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• pp.99-108
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• 2004

본 논문에서는 공장자동화를 위한 제어네트워크로서의 스위칭 이더넷 네트워크의 성능을 분석한다. 스위칭 이더넷은 네트워크상에서의 충돌을 없앰으로써 실시간 데이터의 전송을 가능하게 하여 준다. 공장자동화 제어네트워크는 일반 컴퓨터 네트워크와는 달리 전송되는 데이터의 양은 적은 반면 실시간 전송을 요한다. 본 논문에서는 이더넷 스위치를 이용한 선형 및 트리 토폴로지의 네트워크에서 제어시스템이 요구하는 전송지연시간 요구를 만족하는지에 대해 분석한다.

• 한국정보과학회논문지:시스템및이론
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• 제33권9호
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• pp.684-690
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• 2006

본 논문에서는 스위칭이더넷에서의 주기적 메시지에 대해 경성 실시간 통신을 위한 메시지 전송 모델을 제안하고, 각 메시지들을 마감시간 안에 전송하기 위한 메시지 스케쥴링 알고리즘을 제안한다. 제안하는 스케쥴링 알고리즘은 중앙노드 없이 동작하는 분산 알고리즘이고 스위치에 새로운 기능의 추가없이 송신자와 수신자 노드 사이에서 동작한다. 제안한 알고리즘은 새로운 주기적 메시지에 대한 전송요청이 오면 이미 스케쥴 되어 있는 주기적 메시지에 영향을 미치지 않고 송신 링크와 수신 링크에서 스케쥴링 가능한지 검사를 하고, 스케쥴링이 가능하면 전송 스케쥴을 생성한다. 본 논문에서 제안하는 스케쥴링 알고리즘은 스위칭이더넷에서 주기적 메시지에 대해 마감시간 내 전송을 보장하고, 새로운 메시지에 대한 동적인 추가가 용이하여 경성 실시간 시스템에서 유연한 메시지 전송 기법을 제공한다.

• Journal of Electrical Engineering and Technology
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• 제2권3호
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• pp.379-385
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• 2007

Recently, vital devices of the railway signaling systems have been computerized in order to ensure safe train operation. Due to this computerization, we have gradually come to need networking interfaces between these devices. Thus it is important that there be reliable communication links in the signaling systems. Network technologies are applied in the real-time industrial control system, and there are numerous studies to be carried out on the computer network technology for vital control systems such as railway signaling systems. For deploying the studies, we consider costs, reliability, safety assurance technique, compatibility, and etc. In this paper, we propose the Ethernet for railway signaling systems and also precisely describe the computer network characteristics of vital railway signaling systems. Then we demonstrate the experimental results of the proposed network algorithm, which is based on switched Ethernet technology with redundancy scheme.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2011년도 추계학술대회
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• pp.116-120
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• 2011

본 논문에서는 CAN네트워크와 Profibus 네트워크를 통합하기 위한 통합 프로토콜 게이트웨이를 설계, 구현하였다. CAN/Profibus 네트워크를 통합하기 위하여 스위칭이더넷을 백본 네트워크로 사용하였고, 각각의 필드버스 네트워크는 CAN/Ethernet 및 Profibus/Ethernet 게이트웨이를 이용하여 이더넷 스위치에 연결되며, 각 게이트웨이는 필드버스 프레임과 이더넷 프레임 사이의 변환을 수행한다. 또, 스위칭 이더넷 환경에서 게이트웨이 사이에 분산 경성 실시간 스케줄링 알고리즘을 적용하여 메시지의 실시간성을 만족할 수 있게 하였다. CAN/Ethernet 및 Profibus/Ethernet 게이트웨이 구현을 위해 실시간 메시지 전송을 지원하는 리눅스 2.6.31.12 Real-Time Patch 버전을 사용하였고, 실제 구현을 통해 메시지의 성공적인 변환과 실시간성을 확인할 수 있었다.