Multi-frequency array of nonlinear piezoelectric converters for vibration energy harvesting

Abstract

Energy harvesting from wideband and random vibrations demands for techniques and solutions to overcome limitations of linear converters, which best operate when the frequency of vibrations matches the resonant frequency of the converter. Viable approaches comprise, among others, the use of array of linear harvesters with different resonant frequencies, the adoption of nonlinear techniques or the exploitation of mechanically coupled converters. This work proposes a piezoelectric energy harvester where the combination of such techniques is explored in a unique device. The harvester is composed of an array of four piezoelectric cantilevers fabricated by screen printing lead zirconate titanate (PZT) films on a stainless steel substrate. Nonlinear behavior of the cantilevers is achieved by exploiting the interaction between a magnet and their ferromagnetic steel substrate. Two configurations have been analyzed where the magnet is either fixed on the harvester base, or it is elastically suspended through a spring on the harvester base. The latter configuration introduces a mechanical coupling among the cantilevers. For the experimental characterization, the prototype has been excited by band-pass filtered white-noise mechanical vibrations in the range 10-100 Hz with amplitude in the range 0.1-2.2 g. The obtained experimental results show that the rms values of the open-circuit output voltage for each cantilever increase in the nonlinear configuration and it can be up to 215% higher for the case with the elastically suspended magnet compared to the case of the same array operated in linear regime.

An SECE array of piezoelectric energy harvesting

“…The validation of the proposed SECE harvested power given by equation ( 22) for parallel connection and equation (39) for series connection of piezoelectric oscillators are carried out numerically through the conventional circuit simulation. Indeed, the governing equations of an array system provided by equations ( 1)-( 3) can be explained from the circuit point of view.…”

“…The equivalent model parameters used in the simulations are given by table 1 which was obtained from the experiment presented in the next section. The prediction by the proposed framework is presented by the solid continuous blue line based on equation (22) for the case of parallel connection or equation (39) for the case of series connection. For the purpose of comparison, the electric losses are excluded in the simulations which are presented by various rectangle solid points of blue color.…”

“…Its operational principle is simple enough for covering the frequency range of excitation by adjusting the resonant frequency of each oscillator [35][36][37]. Thus, various forms of harvester arrays were developed for serving specific applications, including the configurations of cantilever [38,39], Z-type beam [40], fan-structure [41], circular diaphragm [42] and MEMS [43]. In spite of these activities developed for broadband energy harvesting, little had paid attention to the inclusion of the power conditioning circuits in these array works [44][45][46].…”

Wearable Ball-Impact Piezoelectric Multi-Converters for Low-Frequency Energy Harvesting from Human Motion

“…Specifically, piezoelectric converters have been extensively investigated in energy harvesting systems for the conversion of mechanical energy produced by human movements into electrical energy useful to power wearable electronics devices [ 31 , 32 , 33 , 34 ]. When operating in linear regime as resonant converters, piezoelectric energy harvesters have the best effectiveness if the input vibration frequencies are close to the resonant frequency of the converter [ 35 , 36 , 37 ].…”

Piezoelectric Energy Harvesting from Low-Frequency Vibrations Based on Magnetic Plucking and Indirect Impacts

“…Many works have been presented in the framework of rotational mechanisms: Pillatsch et al [ 21 , 22 ] realized studies and a prototype for applications on watches; numerical FE-based analyses of the magnetic plucking with experimental studies with rotors have been conducted by Dauksevicius et al [ 23 ]; proof-of-concept of rotational devices in the field of wearable applications with imposed motion have been presented by Kuang et al [ 24 ] in 2015 and by Pozzi et al [ 25 ] in 2016 for knee-joint harvesters. With reference to translational mechanisms, recent investigations on translational actuating mechanisms have been proposed by Li et al [ 26 ], in which a magnet is connected to spring for creating a bandwidth bistable device with amplitude variable potential wells, and by Baù et al [ 27 ], who carried out numerical and experimental investigations on multi-frequency array of transducer interacting with a permanent magnet held or elastically fixed to the supporting base.…”