Vibration analysis of mechanical systems and structures is vital to determine their behaviour in operating conditions and following exceptional events. Therefore, the experimental study of the vibrations of a system (mechanical, aeronautical, civil) is henceforth an essential step in the design and monitoring process. To this end, in addition to traditional measurement tools such as piezoelectric accelerometers, laser movement sensors and laser vibrometers, high speed cameras are a solution for the future, capable of filming large scenes without contact at very high speeds, in the region of thousands of images a second.

Measurements by high-speed cameras permit defining the vibratory fields of a structure, in both transient and stationary regimes, while the use of several cameras surrounding the structure allows measuring its behaviour in 3D, and to detect the oscillations of elements difficult to reach with classical measurement instruments. This is the case for example of the edges of a contact interface in a link, or the free surface of a fluid in a rigid container in movement.

Our studies therefore focus on the utilisation of this new technology, with particular attention given to the following points :

• image processing (binarisation, code optimisation, reduction of calculation time) ;
• detection of features (points, edges, surfaces, fluids) ;
• target tracking ;
• data filtering and assimilation ;
• operational modal analysis by multi-viewpoint 3D ;
• reconstruction of the behaviour of a 3D structure using models and measures ;
• real-time vibration analysis.

More specifically, features can be detected using the image processing algorithms developed, and their movement tracked throughout dynamic tests. Signal filtering and data assimilation techniques provide the information required to perform modal experimental analysis and identify the dynamic properties of the system studied. Our research also aims at developing methods of analysing vibration behaviour in real-time while relying on the synergy between experimental measures and numerical models.

Experimental measurement campaigns are performed in the VAST team’s test laboratory, and in the framework of research projects (FUI CLIMA, EUGENE) and collaborations with academic and industrial establishments (University of Liege, SOPEMEA).

MEASURING FIELDS BY CAMERA IN A FEW MINUTES...