I started my career in 1974 as mechanical engineer in an engineering company (Coppee-Rust) working for the steel industry in the Liege area (cold rolling mill). In 1976 I moved to the nuclear industry (Belgonucléaire) where I specialized in structural dynamics, earthquake engineering, and later in random vibrations. I was mainly concerned with the seismic behaviour of nuclear cores (both PWR and Fast Breeder). I did my Ph.D.from 1978 to 1981 under the supervision of Prof. M. Geradin, while working for Belgonucléaire ; the topic was the « Seismic analysis of pressure water reactor cores » ; it was mainly concerned with nonlinear structural dynamics with impact, but it was also the starting point of my research work in random vibrations. I created a course in Random Vibrations at the University of Liege at about that time. My work on the artificial earthquake generation and on the seismic behaviour of nuclear reactor cores was awarded the International Vinçotte Prize in 1983. Gradually, I got more interested in aerospace and, in 1985, I got an offer to go to the USA as Visiting Professor at the Aerospace and Ocean Engineering Department of Virginia Polytechnic Institute and State University. At the time, there was a tremendous interest in large space structures in the USA, mainly because of the « strategic defense initiative » and the space station program. I stayed there for a year and was initiated to the control of large space structures by Profs. R.Haftka and W.Hallauer ; the former was a world renowned specialist in structural optimization and the latter was, at the time, one of the few experimentalists trying to implement control systems that worked on actual structures. When I returned to Belgium I resumed my job for Belgonucléaire and looked for an academic position. In 1987, I was appointed at the chair of Mechanical Engineering and Robotics of the University of Brussels (ULB). From then on, I shared my time between teaching and research in Structural Dynamics, Control, Robotics, and Mechanical Engineering.

Since my appointment at ULB, my research activities have been devided into three themes :(i) Random vibrations, (ii) Active structures and (iii) Robotics ; they are briefly described below :

(i) Random vibrations :

My book « Vibrations Aléatoires et Analyse Spectrale » was published in 1991 by the « Presses Polytechniques et Universitaires Romandes ». A translated and revised edition was published by Kluwer in 1994 under the title « Random Vibration and Spectral Analysis ».

A software has been developed for spectral analysis of structures subjected to a random environment (both seismic and external loads) ; it has been integrated in a commercial finite element package (SAMCEF) since 1990 and is currently used by numerous industrial companies.

Recent developments have been made in the area of high-cycle fatigue life prediction of metallic structures under multiaxial random loading. An original frequency domain approach has been developed and is currently being extended (with funding from EEC, ESA, SEP, ALENIA-SPAZIO, 1998).

(ii) Active Structures :

When I was appointed at ULB, I decided to start some basic vibration control experiments on my own ; at the same time, the « smart » materials started to become widely available and offered completely new possibilities, particularly for precision structures. On the other hand, they also brought new difficulties in the modeling, due to the strong coupling in their constitutive equations, which requires a complete reformulation of the classical modeling techniques such as finite elements. We therefore started to work simultaneously on modeling, control and experiment. The projects were initially mainly related to space applications, with DORNIER, MATRA MARCONI SPACE, SPACEBEL and ESA as industrial partners. Amongst our early achievements, I would like to point out :

• The first active truss with piezoelectric actuators in Europe (1989),
• The development of a set of control techniques for active damping of flexible structures (1990-1995),
• An in-orbit experiment of active damping of a sandwich piezoelectric plate (successfully flown in september 1995)

The Active Structure Laboratory was inaugurated in November 1995 and my book « Vibration Control of Active Structures, An Introduction » was published by Kluwer in 1997.

Our more recent (ongoing) work covers the control of vibrations ranging from meter (flutter of bridges) to nanometer (precision structures for space telescopes) : I would like to point out

• The active tendon control technology for cable structures, with appications to large cable-stayed bridges (collaboration with BOUYGUES) and to large space trusses (future interferometry missions).
• The development of vibroacoustic control techniques for reducing the noise transmission through flat plates ; this includes the development of a real-time, broad-band noise radiation sensor for acoustic windows, based on a piezoelectric sensor array (collaboration with SAINT-GOBAIN/SAINT-ROCH).
• The development of a large stroke, high precision optical delay line for synthetic aperture telescopes, based on the magnetic bearing technology, which led us to create the spin-off company MICROMEGA to prepare an in-orbit experiment for ESA (1999).

(iii)Robotics

When I was appointed at ULB in 1987, I did not have specific skills in robotics. I started to work on the design and control of walking machines in 1989 ; several prototypes have been constructed and tested. Recently, a micro-rover has been designed as a candidate for space exploration (Mars and comets). Although this activity is pursued with little external funding, it constitutes an excellent support for teaching mechatronics.