Thesis defence: Loïc FORMA

Active vibration control system for preserving heritage objects

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Loïc Forma, a doctoral student at CY Cergy Paris Université, completed his thesis at the SATIE and STMS laboratories (Ircam-Sorbonne Université-CNRS-Ministère de la Culture), the Musée de la musique and the INP (Institut national du patrimoine). He has received funding from the Fondation des sciences du patrimoine.

He will defend his thesis at the INP. The presentation will be in French. The defence can also be followed live through

Jury :

  • Hervé Lissek, Ecole Polytechnique Fédérale de Lausanne, Reporter
  • Patrice Masson, Université de Sherbrooke, Reporter
  • Ioan Doré Landau, GIPSA-lab Grenoble, Examiner
  • Marc Lethiecq, Université de Tours, Examiner
  • Nicolas Wilkie-Chancellier, CY Cergy Paris Université, director
  • Henri Boutin, Sorbonne Université, co-superviser
  • Marguerite Jossic, Musée de la musique, co-superviser
  • Sandie Le Conte, Institut National du Patrimoine, co-superviser
  • Eléonore Kissel, Musée du Quai Branly, invited

Abstract :

In a heritage context, vibrations represent a real threat to the preservation of objects. However, the vibration protection devices used are generally very rudimentary and the systems proposed in the scientific literature are not applied, mainly due to a lack of practical consideration. To overcome these limitations, the work presented in this thesis revolves around the development of a new type of protection system, based on the principle of active vibration control.

The design of the control device begins with the establishment of a specification with a dual objective. On the one hand, it defines the objectives for controlling the vibrations encountered in heritage areas, and on the other, it formalises the practical considerations of those involved in heritage work. The specifications then make it possible to identify the monitoring strategy best suited to meeting the specifications formulated. In this case, the controller is designed as an autonomous, independent device that is grafted onto the structure to be protected, using an adaptive, feedforward control algorithm.

An experimental control device whose controller is updated using the Filtered-x Least Mean Square (FxLMS) algorithm is designed to test its ability to meet the specifications. The device is first tested on a structure with relatively simple dynamics, then on a test bench representative of a situation commonly encountered in a heritage context. Once the system has been validated, a tool for comparing the performance of different control situations quantitatively, objectively and robustly is proposed. This methodology involves extracting performance descriptors, each of which should represent an aspect of control that it is desirable to quantify.

Although the use of FxLMS enables the specifications to be validated, a strong assumption made by this algorithm restricts its field of use. One solution to this limitation is to use more recent control algorithms based on Youla-Kuçera parametrisation. A parametric study defines the conditions above which the performance of FxLMS is no longer acceptable, and the use of the benchmark makes it possible to quantify the performance of the new algorithms proposed.

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