FORMAL MODELLING OF INDUSTRIAL DISTRIBUTED CONTROL SYSTEMS * M. Marcos, E. Estévez *Departamento de Ingeniería de Sistemas y Automática, Universidad del País Vasco, UPV/EHU (Spain) Abstract: Industrial Process Measurement and Control Systems (IPMCS) are used in most of the industrial sectors to achieve production improvement, process optimisation and time and cost reduction. Integration, reuse, flexibility and optimisation are demanded to adapt to a rapidly changing and competitive market. There is also a growing requirement that all software tools that support the different phases of the development process (design, configuration, management) can be integrated as well. Thus, a consolidation of modelling methodologies for achieving this goal is needed. This paper presents a formal modelling for IPMCS that captures all aspects of the system to design in terms of functionality and implementation (hardware and software). The modelling language (eXtensible Markup Language, XML) allow to implement model validation as well as to easily transform information coming from / going to different software tools, achieving tool integration. Copyright © 2005 IFAC Keywords: distributed control systems, formal modelling, programmable logic controllers, industrial applications. 1. INTRODUCTION Nowadays most of the industrial sectors use Programmable Logic Controllers (PLCs) to achieve the control of their productive systems. In the last years, technological advances in these controllers allow the production improvement, process optimisation and time and cost reduction. The application of standards has also a great force in the fast growth of the control and instrumentation of industrial processes. The International Electrotechnical Commission has published several standards promoting interchangeable and open systems. The IEC 61131-3 standard deals with the software model and programming languages for IPCMS. The evolving standard IEC 61499 standard (IEC, 2000) focuses on distributed IPMCS based on an extended definition of Function Blocks and it provides the requirements for software tools to support the specification, analysis and validation of Distributed IPMCS as well as the configuration, implementation, operation and maintenance of such systems. However, as fast as industry reaches a greater maturity level, a consolidation of the modelling methodologies becomes necessary. Therefore, modelling languages, that allow system description and definition before their construction, must be used. The modelling methodology should allow to model the system from different viewpoints as well as to involve the entire system lifecycle. In this sense, PLCopen (PLCopen, 2003) is a vendor- and product-independent worldwide association whose mission is to be the leading association resolving topics related to control programming to support the use of international standards in this field. For this, PLCopen has several technical and promotional committees (TCs). In particular, TC6 for XML had as original goal to define an open interface to communicate different programming tools. But, from the beginning, TC6 members realized that having XML as a common road, other tools, like simulation and modelling tools, or documentation and version control tools could be integrated. Some attempts have been done by different authors towards the use of well known modelling languages for designing IPMCS. Bonfé and Fantuzzi (2000), Heverhagen and Tracht, (2001) propose the use of UML (Jacobson, et al., 1992), (Rumbaugh, et al., 1996) for specifying components of control systems following the IEC 61131-3 standard. But they only model the implementation issues for this software model and their goal is to generate source code. There are other works that focus on the design of