Abstract
The paper aims to assess and improve the performances of a multilayer piezoelectric MEMS device for vibrations harnessing. Two operating modes are possible: at resonance and outside resonance. In some applications it is not possible to operate at resonance, functioning being mostly at low frequencies in a quasi-static regime. An Euler-Bernoulli classic beam theory mathematical model was studied for estimating the behaviour of multilayer piezoelectric generators, in terms of deflection and voltage, at functioning under resonance frequency. The analytical results were compared with the finite element method simulation in COMSOL Multiphysics. The main goal of this study is to obtain an accurate model for engineering design purposes, with simple analytical equations and ease of use, but with predictable errors. The study proved the usefulness of the derived model but also its limitations. It also proves the need to improve the model using plate theory, for sensors with high width/height ratio.
Highlights
Different transduction mechanisms have been studied for converting vibrations into electricity, but piezoelectric energy harvesting has received the most attention due to the high power density and ease of application [1]
The total voltage in the two piezoelectric layers and the maximum mechanical stress, calculated as functions of force
For all the considered values of the force applied at the free end on a direction perpendicular to the surface (z-direction): the electric field in the piezoelectric layers, the voltage differences between central layer declared as ground and the upper and lower layer declared as terminals, the deformations, the distribution of stress tensor component on x direction evaluated in the piezoceramic layers, and the maximum overall stress in the piezoceramic layers, computed with von Mises relations
Summary
Different transduction mechanisms (piezoelectric [1,2,3,4], electromagnetic [4,5,6], electrostatic [7,8]) have been studied for converting vibrations into electricity, but piezoelectric energy harvesting has received the most attention due to the high power density and ease of application [1]. Operating at resonance enables energy harvesters to be placed on equipment producing high vibrations (engines, compressors, turbines, etc.). The transducer does not support the external mass and force, this being the role of a flexible mechanical suspension, but is actuated during suspension movement In this case the regime is quasi-static, the operating frequency being very low comparing with the resonance frequency
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