IEEE Industrial Electronics Society
IEEE Industrial Electronics Society
May 17, 2006
Editorial-Special Issue on Communication in Automation
Sauter, T. Vasques, F.
Page(s): 73-77
1. "An Active Star Topology for Improving Fault Confinement in CAN Networks"
Barranco, M. Proenza, J. Rodriguez-Navas, G. Almeida, L.
Page(s): 78-85
Abstract - The controller area network (CAN) is a field bus that is nowadays widespread in distributed embedded systems due to its electrical robustness, low price, and deterministic access delay. However, its use in safety-critical applications has been controversial due to dependability limitations, such as those arising from its bus topology. In particular, in a CAN bus, there are multiple components such that if any of them is faulty, a general failure of the communication system may happen. In this paper, we propose a design for an active star topology called CANcentrate. Our design solves the limitations indicated above by means of an active hub, which prevents error propagation from any of its ports to the others. Due to the specific characteristics of this hub, CANcentrate is fully compatible with existing CAN controllers. This paper compares bus and star topologies, analyzes related work, describes the CANcentrate basics, paying special attention to the mechanisms used for detecting faulty ports, and finally describes the implementation and test of a CANcentrate prototype.
2. "On the Properties of the Flexible Time Division Multiple Access Technique"
Cena, G. Valenzano, V.
Page(s): 86-94
Abstract - Flexible time division multiple access (FTDMA) is a medium access mechanism that some modern popular networks for use in passenger vehicles, such as Byteflight and FlexRay, rely on. Its development was driven explicitly by the new needs of automotive x-by-wire systems, which could not be satisfied by the existing solutions. The FTDMA technique was conceived primarily to overcome the limitations of controller area network and, in particular, for supporting high performance real-time communications. Even though this access scheme is mainly suitable for asynchronous transmissions, it can be adopted profitably for synchronous exchanges as well. In this paper, the main features of FTDMA are analyzed, and its performance is evaluated for different kinds of communications that have to be supported in today's vehicles.
3. "Combining Operational Flexibility and Dependability in FTT-CAN"
Ferreira, J. Almeida, L. Fonseca, J.A. Pedreiras, P. Martins, E. Rodriguez-Navas, G. Rigo, J. Proenza, J.
Page(s): 95-102
Abstract - The traditional approaches to the design of distributed safety-critical systems, due to fault-tolerance reasons, have mostly considered static cyclic table-based traffic scheduling. However, there is a growing demand for operational flexibility and integration, mainly to improve efficiency in the use of system resources, with the network playing a central role to support such properties. This calls for dynamic online traffic scheduling techniques so that dynamic communication requirements are adequately supported. Nevertheless, using dynamic traffic management mechanisms raises additional problems, in terms of fault-tolerance, related with the weaker knowledge of the future system state caused by the higher level of operational flexibility. Such problems have been recently addressed in the scope of using flexible time-triggered CAN (FTT-CAN) in safety-critical applications in order to benefit from the high operational flexibility of this protocol. This paper gathers and reviews the main mechanisms that were developed to provide dependability to the protocol, namely, master replication and fail-silence enforcement.
4. "Automated Modeling and Analysis of CSMA-Type Access Schemes for Building Automation Networks"
Ploennigs, J. Buchholz, P. Neugebauer, M. Kabitzsch, K.
Page(s): 103-111
Abstract - During the design of large technical systems, the use of analytic and simulative models to test and dimension the system before implementation is of practical importance for an efficient and reliable design process. However, setting up the necessary models is time-consuming and therefore often too expensive in practice. Usually most information for modeling is already available in the design tool used to develop such extensive systems and only needs to be extracted for automatic model building. This paper presents an automated modeling approach from an existing design database using the example of a network analysis for building automation fieldbuses. The analysis is based on an analytical decomposition approach that enables fast estimation of performance measures for large-scale networks. The combination of fast analytical algorithms with automatic model generation allows network performance engineering with minimized effort for model generation and analysis.
5. "Providing Real-Time Applications With Graceful Degradation of QoS and Fault Tolerance According to$(m, k)$-Firm Model"
Li, J. Song, Y. Simonot-Lion, F.
Page(s): 112-119
Abstract - The$(m, k)$-firm model has recently drawn a lot of attention. It provides a flexible real-time system with graceful degradation of the quality of service (QoS), thus achieving the fault tolerance in case of system overload. In this paper, we focus on the distance-based priority (DBP) algorithm as it presents the interesting feature of dynamically assigning the priorities according to the system's current state (QoS-aware scheduling). However, DBP cannot readily be used for systems requiring a deterministic$(m, k)$-firm guarantee since the schedulability analysis was not done in the original proposition. In this paper, a sufficient schedulability condition is given to deterministically guarantee a set of periodic or sporadic activities (jobs) sharing a common non-preemptive server. This condition is applied to two case studies showing its practical usefulness for both bandwidth dimensioning of the communication system providing graceful degradation of QoS and the task scheduling in an in-vehicle embedded system allowing fault tolerance.
6. "Vertical Integration of Enterprise Industrial Systems Utilizing Web Services"
Kalogeras, A.P. Gialelis, J.V. Alexakos, C.E. Georgoudakis, M.J. Koubias, S.A.
Page(s): 120-128
Abstract - The need for interoperability is prominent in the industrial enterprise environment. Different applications and systems that cover the overall range of the industrial infrastructure from the field to the enterprise level need to interoperate. This quest is driven by the enterprise need for greater flexibility and for the wider possible integration of the enterprise systems. This paper presents a distributed system architecture that utilizes dominant state-of-the-art standard technologies, such as workflows, ontologies, and web services, in order to address the above quest in an efficient way.
7. "On the Use of Wireless Networks at Low Level of Factory Automation Systems"
De Pellegrini, F. Miorandi, D. Vitturi, S. Zanella, A..
Page(s): 129-143
Abstract - Wireless communication systems are rapidly becoming a viable solution for employment at the lowest level of factory automation systems, usually referred to as either "device" or "field" level, where the requested performance may be rather critical in terms of both transmission time and reliability. In this paper, we deal with the use of wireless networks at the device level. Specifically, after an analysis of the communication requirements, we introduce a general profile of a wireless fieldbus. Both the physical and data link layers are taken directly from existing wireless local area networks and wireless personal area networks standards, whereas the application layer is derived from the most popular wired fieldbuses. We discuss implementation issues related to two models of application layer protocols and present performance results obtained through numerical simulations. We also address some important aspects related to data security and power consumption.
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