Abstract
The purpose of this work is to improve the modelling process for the application of permanent magnets in a frequency up-conversion (FuC) mechanism for piezoelectric energy harvesters. More specifically, the aim is to avoid the burdensome finite element analyses (FEA) in the framework of electromechanical devices design. The analytical calculations are compared with experimental tests conducted by an ad-hoc set up and with FEA. After investigations on the interaction, an application of FuC mechanism is proposed on a meso-scale case study in which a low frequency seismic mass (LFM) interacts non-linearly, due to magnetic field, with an high frequency piezoelectric vibration energy harvester (PVEH). Numerical simulations have been carried out in the time domain (step-by-step analysis) under a harmonic low-frequency input acceleration signal. The peculiar behavior, due to non-linear dynamics, is investigated in both the repulsive and the attractive configurations of the magnets. The results confirm the effectiveness of magnetic FuC and show that the repulsive case allows the device to recover a larger amount of energy than the attractive configuration.
Highlights
The development of energetically autonomous MicroElectro-Mechanical Systems (MEMS) sensors paves the way for the creation of large networks of devices, with no need for wires or batteries
The present paper is focused on the investigation of magnetic interaction for frequency up-conversion in piezoelectric energy harvesters
This formula is quite poor in the representation of the Fy component and it requires two fitting parameters ( F0 and de ) making necessary experimental data or finite element simulations
Summary
The development of energetically autonomous MicroElectro-Mechanical Systems (MEMS) sensors paves the way for the creation of large networks of devices, with no need for wires or batteries To this purpose, the available kinetic energy in the environment could be transformed into electrical energy, through suitable energy harvesting systems, e.g. by means of piezoelectric transduction [1,2,3]. The energy content of the environment, in which MEMS operate, is distributed over a low-frequency spectrum (e.g. 0–100 Hz [4, 5]) and the piezoelectric vibration energy harvesters (PVEHs in the following) are characterized by high natural frequency of vibrations. 5, numerical simulations of the harvesting system are presented on a realistic meso-scale case study with the permanent magnets of the FuC core both in repulsive and in attractive configurations under harmonic acceleration of the device.
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