Ethernet in Automation: Technological Advances towards Real-time Communication

Abstract
In modern process control systems the different activities are organised by structuring a plant as a hierarchy of functional levels. In order to take into account the different requirements of the traffic exchanged at the various levels in the hierarchy, communication architectures are also organised as levels of networks using different communication protocols according to their specific operating conditions. The heterogeneous nature of these networks, however, causes problems of incompatibility and complicate the exchange of information between different levels. For this reason, manufacturers and users are currently showing great interest in harmonising the communication infrastructure at the plant level. In this context, Ethernet technology seems to be the most natural candidate for a number of practical and economic reasons. Ethernet is thus achieving a leading position, proposing itself as a network capable of supporting all communication needs at all levels in the control hierarchy. At present, Ethernet generally supports communication related to activities which require bandwidth exploitation as well as throughput maximisation and can tolerate non deterministic access times. This is due to the contention-based medium-access control protocol of Ethernet, which cannot provide individual nodes with a predictable medium access time.

However, in the last few years, increasing interest has arisen in the use of Ethernet networks even at the field level, where time-critical communication between sensors, controllers and actuators is currently supported by suitable bus-based networks called Fieldbuses. After a description of the network infrastructures typically used in process control environments, the speech will focus on the use of Ethernet as a single network technology for the whole process control system. It will be outlined how to use switches and hubs for the interconnection of the various nodes/devices in order to simplify data exchange while providing, when required, real-time performance. Then, suitable approaches to improve timeliness in the delivery of real-time data over a Shared Ethernet network will be discussed and their performance, obtained by simulation, will be compared.

Biography:
Dr. Lucia Lo Bello received a M.S. Degree in Electronic Engineering and a Ph.D. in Computer Engineering from the University of Catania in 1994 and 1998, respectively. Starting from 1997/98, she was awarded several lectureships at the Universities of Catania and Messina respectively and a 4-year research scholarship by the Faculty of Engineering, University of Catania, for the research project entitled "Advanced Systems and Technologies for Distributed Information Management in Real-Time Environments". From August 2000 to Feb. 2001, Dr. Lo Bello was awarded a post-doctoral position as a Visiting Researcher at the College of Engineering of Seoul National University, Seoul, South Korea, to conduct research on real-time distributed systems.

Since June 2001, Dr. Lucia Lo Bello is Assistant Professor at the Department of Computer Engineering and Telecommunications, University of Catania, Italy.

Dr. Lo Bello’s current research activity focuses on Real-Time systems, with particular interest in communication and scheduling issues. Among other research interests, time-critical networks for process control (Fieldbuses), distributed operating systems and real-time databases. Part of Dr. Lo Bello’s research activity has been carried out for national and international research projects. Dr. Lo Bello’s research activity has resulted in the publication of a number of papers in conference proceedings and in international journals.

Home page: http://www.diit.unict.it/users/llobello/