Foreword Large-scale systems have been traditionally characterized by a large number of variables, nonlinearities and uncertainties. Their decomposition into smaller, more manageable subsystems, possibly organized in a hierarchical form, has been associated with intense and time-critical information exchange and with the need for efficient co-ordination mechanisms. The last decade of the past century and the beginning of the 21st century have revealed new characteristic features of industrial and non-industrial large-scale systems.

The enterprise of the present time are to operate in a highly networked environment and there is an ever more increased concern for integration of various technologies and for economic, environmental and social aspects. Consequently the design of control systems must take into account more aspects and needs additional skills and tools. At the same time, the recent advances in computer and communication technologies can provide effective tools and adequate technical infrastructures to support the design and implementation of control systems for the large-scale applications of the present time.

This volume contains the papers presented at the 9th IFAC Symposium on “Large Scale Systems: Theory and Applications” - LSS 2001, held in Bucharest, Romania in the period 18 - 20 July 2001.

LSS 2001 was the ninth edition of a by now traditional symposium with the inaugural edition being held at Udine, Italy, in 1976. Since then, at a three-year succession, the Symposium took place in Toulouse (1980), Warsaw (1983), Zurich (1986), Berlin (1989), Beijing (1992), London (1995) and Patras, Greece (1998). The event was sponsored by the IFAC Technical Committee on Large scale Systems and was co-sponsored by the IFAC Technical Committees on Manufacturing, Modeling, Management and Control, Advanced Manufacturing Technology and Man-Machine Systems. The Symposium was co-organised by the National Institute for R&D in Informatics ICI and the “Politehnica” University of Bucharest (PUB), and was held within the premises of PUB. 

The Symposium addressed the control aspects of industrial, economic, social and environmental systems of which characteristics are high dimensionality, non linearity and uncertainty, associated with a multitude of structural forms, with intense and time critical information exchange and efficient co-ordination. It aimed at covering major aspects of large scale, complex systems including methodological aspects, technological solutions and practical applications.

The Symposium Final Programme included 109 papers (out of 114 accepted), to be presented in regular, invited and plenary sessions. 

68 regular papers were selected (after reviews of the full texts), from as many as 80 which had been submitted. Based on the final versions received, 64 regular papers were included in the Final Programme under 12 technical sessions.

The necessity for striking a fair balance between the technical sessions addressing methodological aspects and those devoted to practical applications encouraged the organizers to ask distinguished scientists from the Czech republic, Japan, Romania, Switzerland and the UK to organize invited sessions. 40 papers were included in the final programme under eight invited sessions.

This volume contains the papers ordered in accordance with the technical sessions.

Session topics included methodology and application fields, currently traditional for the LSS events over the years:

• Modeling and model reduction;
• Decentralized control and estimation;
• Hierarchical control;
• Intelligent and fuzzy control;
• Nonlinear dynamics in complex systems;
• Complex systems theory and analysis;
• Water, gas, power systems;
• Large scale CIMs and production planning and scheduling;
• Communication and information systems;
• Transportation systems;
• Modeling and control of wastewater treatment plants;
• Societal systems modeling, planning and management.

In addition, several, less traditional session topics were included in the technical programme, such as:

• Decision support systems;
• Risk and governance in large-scale systems.

Five high reputed speakers presented plenary papers of broad and general interest in the LSS field, or communicated new approaches and emerging technologies at the turning of the century:

Prof. Christos Cassandras, from the Boston University, USA, spoke about how complexity can be made simple at a small price.
Prof. George Metakides, from the European Commission DG “Information Society”, presented the emerging technologies for ambient intelligence.
Prof. Peter David Roberts, from the City University London, UK, took an overview of various techniques for integrated systems optimization and parameter estimation.
Prof. Masao Ikeda, from Osaka University, Japan, lectured on vibration suppression design of adaptive structures.
Prof. Peter Groumpos, from Patras University, Greece, made a comprehensive analysis of issues and challenges in multilevel hierarchical systems and intelligent control.

115 participants from 17 countries registered with the Symposium. They represented universities, R&D institutes and engineering companies. The participants presented 53 regular papers, 35 invited papers and 5 plenary papers.

It can be appreciated that several subfields that are traditional for LSS events remain of interest to the scientific community, such as hierarchical and decentralized control, model reduction and optimization. Other subfields traditionally of interest to the LSS community, such as decomposition and stability, were less represented at the conference. Traditional applications of LSS methods, such as power, gas, transportation, manufacturing, water systems are still of interest. Other traditional application domains, such as agriculture, process industry, robotics were scarcely represented. The new issues such as risk management and human decision in LSS were well received by the participants. Among main ideas and trends one can include: a) large systems become ever larger (more complicated and networked) and b) there is still a need for practical solutions, possibly including new technologies with a view to attaining a correct balance between control techniques and computer and communication tools.

Even though the vast majority of participants were from academia, their papers (including several methodology-oriented ones) described actual applications. It is felt however that efforts should be further made to implement the new developed methods and techniques into industrial products. Also, the current information and communication technologies are to be applied to a larger extent to solve the new problems of networked systems of the current day.

Acad. F.G. Filip Prof. I. Dumitrache Prof. S.St. Iliescu