IEEE Industrial Electronics Society
IEEE Industrial Electronics Society
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Introducing Associate Editor – Sam Kwong
Guest Editorial: Special Section on Communication in Automation
Gianluca Cena and Françoise Simonot-Lion
1. A Proposal for a Generic Real-Time Ethernet System
Juergen Jasperneite; Jahanzaib Imtiaz; Markus Schumacher; Karl Weber
Abstract: After the introduction of fieldbus technology real-time Ethernet (RTE) systems now form the second generation of industrial communication systems (2G ICS). A lot of different approaches for RTEs appeared during the last years, most of them optimized for specific use cases or application domains. From a user’s perspective, the transition from a proved fieldbus system to a RTE only makes sense, if multiple system properties are improved significantly in comparison to the state of the art. In order to address such main requirements of machine builders, we introduced three building blocks as key components for a generic RTE system, these includes topology-based addressing, optimized datagram transfer and synchronous scheduling
2. Analysis of Ethernet Powerlink Wireless Extensions Based on the IEEE 802.11 WLAN
Lucia Seno; Stefano Vitturi; Claudio Zunino
Abstract: The industrial communication scenario is experiencing the introduction of wireless networks at all levels of factory automation systems. The benefits deriving from such an innovation are manifold, even if wireless systems can not be thought as a complete replacement of wired networks. Rather, they will be even more used in the near future to realize hybrid (wired/wireless) configurations. In particular, it is envisaged that wireless networks may be employed to implement extensions of (possibly already installed) wired systems. In this paper we consider wireless extensions of Ethernet Powerlink, a very popular Real--Time Ethernet network, implemented by means of the IEEE 802.11 WLAN. Specifically, we focus on a widespread network configuration and address two types of extensions based on, respectively, bridge and gateway devices. In the second part of the paper we provide an analysis of the hybrid networks aimed at evaluating the most relevant performance indexes. Since the reliability of wireless networks may represent a critical aspect, the analysis is carried out taking into account the presence of interference as well as fading in the wireless segment. The results we show, obtained from a theoretical analysis and validated by numerical simulations, allow to get some useful insights on the overall performance of the hybrid networks.
3. Time driven Access and Forwarding for industrial wireless multi-hop networks Marchetto Guido; Baldi Mario; Giacomelli Riccardo;
Abstract: The deployment of wireless technologies in industrial networks is very promising mainly due to their inherent flexibility. However, current wireless solutions lack the capability to provide the deterministic, low delay service required by many industrial applications. Moreover, the high level of interference generated by industrial equipment limits the coverage that ensures acceptable performance. Multi-hop solutions, when combining frame forwarding with higher node density, have the potential to provide the needed coverage while keeping radio communication range short. However, in multi-hop solutions the medium access time at each of the nodes traversed additively contributes to the end-to-end delay and the forwarding delay (i.e., the time required for packets to be processed, switched, and queued) at each node is to be added as well. This paper describes Time-driven Access and Forwarding (TAF), a solution for guaranteeing deterministic delay, at both the access and forwarding level, in wireless multi-hop networks, analyzes its properties, and assesses its performance in industrial scenarios.
4. Enhancing Real-Time Delivery in Wireless Sensor Networks with Two-Hop Information
Li Yanjun; Chen Chung Shue; Song Ye-Qiong; Wang Zhi; Sun Youxian
Abstract: A two-hop neighborhood information based routing protocol is proposed for real-time wireless sensor networks. The approach of mapping packet deadline to a velocity is adopted as that in SPEED; however, our routing decision is made based on the novel 2-hop velocity integrated with energy balancing mechanism. Besides, initiative drop control is embedded to enhance energy utilization efficiency while reducing packet deadline miss ratio. Simulation and comparison show that the new protocol has led to lower packet deadline miss ratio and higher energy efficiency than two existing popular schemes. The result has also indicated a promising direction in supporting real-time QoS for wireless sensor networks.
5. Average Channel Utilization of CSMA with Geometric Distribution under Varying Workload
Marek Miśkowicz
Abstract: Performance analysis of fixed-size contention window CSMA protocol with geometric distribution for slot selection probability is addressed in the paper. This MAC scheme, called Sift, was initially proposed for large-scale event-driven wireless sensor networks. The goal of the present paper is to evaluate the standard performance measures (throughput, protocol capacity, collision rate, and mean access delay) for geometrically distributed CSMA both in the context of data-centric dense sensor networks and node-centric industrial automation systems. The analytical approach based on the stochastic analysis has been applied. To demonstrate how the protocol is able to cope with bursty traffic, the average throughput defined over a specified workload range has been introduced and examined. Using the average throughput as the performance criterion, the geometric CSMA has been compared to conventional CSMA schemes with uniform distribution. The latter are represented by the classical p-persistent CSMA and the predictive p-persistent CSMA used in LonWorks control networks. It is shown that G-CSMA is overload-tolerant event-driven MAC protocol since the average throughput may be kept on high level in wide range of workload if the shape of geometric distribution is well chosen.
6. Safely Stimulating the Clock Synchronization Algorithm in Time-Triggered Systems – a Combined Formal & Experimental Approach
Matthias Fuegger, Eric Armengaud1; Andreas Steininger
Abstract: Deterministic replay is used during testing to reproduce a scenario and drive the system under test to a given state. In this work, we replay an a-priori defined bus traffic to influence the clock synchronization mechanism. Beyond testing this distributed mechanism itself, our aim is to draw conclusions on the nodes' bus receiver operation. Since these replay activities are part of a transparent online test procedure, it is important to ensure that they do not represent a threat for proper system operation. We show this for TTP/C by means of a generic formal proof, while for the case of FlexRay we formally prove that the system precision can be bounded according to the replay operation applied. Experimental results confirm and illustrate our approach.
7. Software Agents in Industry: A Customized Framework in Theory and Praxis
Sebastian Theiss; Volodymyr Vasyutynskyy; Klaus Kabitzsch
Abstract: Recently, distributed agents are increasingly adopted in automation control systems, where they are used for monitoring, data collection, fault diagnosis and control. However, existing agent platforms do not always fulfill the requirements of practical automation applications in respect of real-time proper ties and resource usage. Often, they offer a lot of functionality that is not necessary in automation and leads to significant overhead in respect of design effort and runtime resources. To meet the specific requirements of the automation domain, a resource-efficient agent platform was developed, which relies on established concepts of agent platforms, but modifies and supplements them accordingly. This platform is implemented in Java and in several C++ variants. This paper describes the architecture of the platform and discusses several performance issues. Results of various performance tests are presented in comparison to the established agent platform JADE. Finally, a practical use case is presented, where the platform is utilized to drive a hardware-in-the-loop emulation and testing environment.
8. Coexistence Issues of Multiple Co-located IEEE 802.15.4/ZigBee Networks Running on Adjacent Radio Channels in Industrial Environments
Lucia Lo Bello, Lucia, and Emanuele Toscano
Abstract: The characteristics of the IEEE 802.15.4 physical and medium access layers make such a protocol a suitable candidate to support communication between sensors and actuators in industrial environments. As industrial networks may comprise a large number of sensors and actuators and the delay increases with the increased number of nodes, a possible solution to keep the delay small is the use of multiple radio channels to implement different small low-latency communication cells. Although in IEEE 802.15.4 the radio channels do not overlap, recent literature showed that some interference may actually occur. This paper provides a better understanding of cross-channel interference in co-located IEEE 802.15.4 industrial networks and proposes a general methodology for the assessment of IEEE 802.15.4 performance under different cross-channel interference conditions. This methodology allows a network designer to perform on-site but accurate assessments and can be easily deployed in real industrial environments to perform measurements directly in the environment-under-test. A case study based on COTS IEEE 802.15.4 devices is presented to show how to apply our methodology to a real scenario and to discuss the results obtained with one or multiple interferers and varying some MAC level parameters.
9. Computation of Performance Bounds for Real-Time systems using Time Petri Nets
Simona Bernardi, and Javier Campos
Abstract: Time Petri Nets (TPNs) have been widely used for the verification and validation of real-time systems during the software development process. Their quantitative analysis consists in applying enumerative techniques that suffer the well known state space explosion problem. To overcome this problem several methods have been proposed in the literature, that either provide rules to obtain equivalent nets with a reduced state space or avoid the construction of the whole state space. In this paper, we propose a method that consists in computing performance bounds to predict the average operational behavior of TPNs by exploiting their structural properties and by applying operational laws. Performance bound computation was first proposed for Timed (Timed PNs) and Stochastic Petri nets (SPNs). We generalize the results obtained for Timed PNs and SPNs to make the technique applicable to TPNs and their extended stochastic versions: TPN with firing frequency intervals (TPNFs) and Extended TPNs (XTPNs). Finally, we apply the proposed bounding techniques on the case study of a robot-control application taken from the literature.
10. Detecting Chains of Vulnerabilities in Industrial Networks
Manuel Cheminod, Ivan Cibrario Bertolotti, Luca Durante, Paolo Maggi, Davide Pozza, Ricardo Sisto, and Adriano Valenzano
Abstract: In modern factories, personal computers are starting to replace traditional Programmable Logic Controllers, due to cost and flexibility reasons, and also because their operating systems now support programming environments even suitable for demanding real-time applications. These characteristics, as well as the ready availability of many software packages covering any kind of needs, have made the introduction of PC-based devices at the factory field level especially attractive. However, this approach has a profound influence on the extent of threats that a factory computing infrastructure shall be prepared to deal with. In fact, industrial personal computers share the same kinds of vulnerabilities with their office automation counterparts. Then, their introduction increases the risk of cyber-attacks. As the complexity of the network grows, the problem rapidly becomes hard to tackle by hand, due to the subtle and unforeseen interactions that may occur among apparently unrelated vulnerabilities, thus bearing the focus on the full automation of the analysis. Going into this direction, this paper presents a software tool that, given an accurate and machine-readable description of vulnerabilities, detects whether or not they are of concern and evaluates consequences in the context of a factory network.
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