1,721,043 research outputs found
Total harmonic distortion estimation in piezoelectric micro-electro-mechanical-system loudspeakers via a FEM-assisted reduced-order-model
No full textPiezoelectric micro-electro-mechanical-system (MEMS) loudspeakers are attracting growing research interest in the last years due to the increasing interest towards miniaturization required by new wireless audio devices. Finite Element Models (FEM) and Lumped Element Models (LEM) able to accurately simulate their linear response have been recently proposed in the literature. However, a nonlinear model suitable to predict the Total Harmonic Distortion (THD) of these devices is to date still missing. In this work, we present a FEM-assisted lumped-parameters equivalent circuit for THD estimation which accounts for geometric nonlinearities and piezoelectric hysteresis. The loudspeaker nonlinear electro-mechanical domain is simulated through a Reduced Order Model (ROM) which considers as basis function the pre-stressed undamped actuated mode of the device computed via FEM, to account for loudspeaker diaphragms of arbitrarily complex geometry. Parameters of the acoustical circuit are computed through analytical formulas. The good matching between numerical predictions and experimental results, carried out on a piezoelectric MEMS loudspeaker prototype for in-ear condition, demonstrates the accuracy of the proposed tool
Synthesis of auxetic structures using optimization of compliant mechanisms and a micropolar material model
Full text linkAim of this work is the synthesis of auxetic structures using a topology optimization approach for micropolar (or Cosserat) materials. A distributed compliant mechanism design problem is formulated, adopting a SIMP–like model to approximate the constitutive parameters of 2D micropolar bodies. The robustness of the proposed approach is assessed through numerical examples concerning the optimal design of structures that can expand perpendicularly to an applied tensile stress. The influence of the material characteristic length on the optimal layouts is investigated. Depending on the inherent flexural stiffness of micropolar solids, truss–like solutions typical of Cauchy solids are replaced by curved beam–like material distributions. No homogenization technique is implemented, since the proposed design approach applies to elements made of microstructured material with prescribed properties and not to the material itself
A novel low-frequency multi-bandgaps metaplate: Genetic algorithm based optimization and experimental validation
No full textMetaplates, i.e. 2D extruded structures made by a periodic repetition of unit cells that exhibit a complete and wide 3D bandgap, are attracting increasing interest thanks to the variety of emerging applications. In this work, an innovative planar unit cell suitable for metaplates is proposed and optimized through a genetic algorithm, to achieve wide and low frequency bandgaps. Four objective functions are employed to show the potentiality of the proposed topology with respect to the state of the art. Metaplates obtained through the periodic repetition of the optimized unit cells are then simulated and experimentally tested. High performance metaplates, endowed e.g. with a nondimensional opening frequency of 0.0029 and bandgap width equal to 95%, are here obtained, thus opening the path to challenging applications also in the world of Micro-Electro-Mechanical Systems (MEMS)
SMART MATERIALS AND METAMATERIALS FOR MEMS: A GROWING TREND IN MICROSYSTEMS TECHNOLOGY
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Sensitivity and temperature behavior of a novel z-axis differential resonant micro accelerometer
Full text linkGIROSCOPIO TRIASSIALE MEMS A MODULAZIONE DI FREQUENZA
No full textLa presente invenzione riguarda un giroscopio triassiale MEMS a modulazione di frequenza (FM) totalmente differenziale. La struttura meccanica del giroscopio è costituita da due masse inerziali che possono traslare rispetto al substrato nelle tre direzioni.
La stessa struttura meccanica può essere impiegata per un giroscopio biassiale (pitch-roll o roll-yaw o yaw-pitch) a modulazione di ampiezza (AM), totalmente differenziale
Interpolation Based Reduced Order Modelling for Non-linearities in MEMS
No full textIn this paper a numerical Reduced Order Modelling (ROM) procedure able to simulate Micro-Electrical-Mechanical-Systems (MEMS) devices featuring electrostatic and geometric non-linearities is proposed. The main idea is to model MEMS devices as composition of stiff components, compliant elements and electrodes. Consequently, the problem dimensionality is determined by the degrees of freedom (dof) of the stiff components. Elastic and electrostatic forces are modelled through a mapping procedure that consists in the interpolation or fitting of numerically precomputed tables. The ROM is applied to the analysis of a MEMS quad-mass structure and validated with experimental data
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