Hichem Nouira

Energy harvesting using vibrating structures excited by shock

Energy scavenging research shows a growing interest these last years. This paper aims to demonstrate the ability of micromachined vibrating structures to store mechanical energy and then to convert it into electrical energy through a piezoelectric plate. Such a micro power generator may be used as a mechanical to electrical energy transformer. The energy conversion consists in a mechanical shock enabling to convert low vibrating energy levels at very low frequencies (typically below 10 Hz for human being excitation source) to mechanical energy to the vibrating structure for which resonant frequencies are ranging from 10 kHz to 1 MHz. Moreover this basic low frequencies to high frequencies spectrum conversion enables to avoid frequency tuning designing that is required for adapting the frequency spectrum of the excitation source.

3F-4 Experimental Evidence and Modeling of Microsliding on Cantilever Quartz Beam

The design of mechanical systems requires various studies in order to ensure an optimal behavior during operation. In particular, the study of its dynamic behavior makes it possible to evaluate the role of a connection in the energy dissipation mechanisms. In this context, an experimental setup dedicated to small structures has been developed to quantify damping due to microsliding at the beam-clamp interface. The mechanical characterization of the clamped connection is carried out by experimental dynamic tests on a free-clamped structure. The instantaneous frequencies and damping are identified by the wavelet transform technique of a slightly non-linear system. In parallel, numerical prediction of the equivalent damping is achieved thanks to the implementation of the regularized Coulomb law in a finite element model. A genetic algorithm and artificial neural networks are used to update the stiffness parameter and the friction coefficient. The optimized model is in good agreement with experimental results. It allows for determining the spatial distribution of microsliding and tangential force along the contact interface. The dissipated energy and equivalent damping are finally deduced according to the dynamic deflection of the free part of the beam.

P2E-4 Energy Harvesting Using Composite Silicon/Lithium Niobate Vibrating Structures

Energy scavenging research shows a growing interest these last years. This paper describes all the potential energy losses in an energy harvesting device. Such a micro power generator may be used as a mechanical to electrical energy transformer. A finite element piezoelectric optimization is performed on a cantilever structure and enables to show the best location for the piezoelectric plate.