This paper investigates a new application of nonlinear techniques for vibration energy harvesting. The Synchronous Electric Charge Extraction (SECE) energy harvesting technique for piezoelectric ...generators is extended and adapted to electromagnetic generators. This new circuit, which is the dual of the SECE circuit, is named SMFE for Synchronous Magnetic Flux Extraction. A theoretical model is developed, and the harvested power is simulated. Comparisons with a classical energy extraction approach show that between 2.5 more power and 10% less power can be harvested, depending on the generator characteristics. It also allows the maximum power to be harvested whatever the value of the load. Finally, the SMFE circuit was embedded and tested on a simple centimeter-scale electromagnetic harvester. Measurements confirm the theoretical operating principle of the circuit.
A normalized model for piezoelectric and electromagnetic vibration energy harvesters is described, allowing a unique expression of the harvested power to be written. The normalization used points out ...three characteristic parameters of any generator: its coupling coefficient, its losses coefficient and its mechanical quality factor. The evolution of the normalized harvested power is theoretically studied as a function of these parameters. Experimental results and a bibliographic study present typical orders of magnitude of coupling and losses coefficients values for piezoelectric and electromagnetic generators, and put forward unusual dualities: while piezoelectric generators have low coupling and low losses coefficients, electromagnetic generators exhibit high resistive losses compensated by high coupling coefficients. For both generators almost the same normalized power can be harvested with these dual parameters. Finally, the scaling effect is investigated: it is notably shown that the power density of an electromagnetic generator does not decrease proportionately with its volume as it is commonly accepted.
This paper presents a comparison between four vibration-powered generators designed to power standalone systems, such as wireless transducers. Ambient vibrations are converted into electrical energy ...using piezoelectric materials. The originality of the proposed approaches is based on a particular processing of the voltage delivered by the piezoelectric material, which enhances the electromechanical conversion. The principle of each processing circuit is detailed. Experimental results confirm the predictions given by an electromechanical model: compared to usual generators, the proposed approaches dramatically increase the power of the generators.
This paper presents a new technique of electrical energy generation using mechanically excited piezoelectric materials and a nonlinear process. This technique, called synchronized switch harvesting ...(SSH), is derived from the synchronized switch damping (SSD), which is a nonlinear technique previously developed to address the problem of vibration damping on mechanical structures. This technique results in a significant increase of the electromechanical conversion capability of piezoelectric materials. Comparatively with standard technique, the electrical harvested power may be increased above 900%. The performance of the nonlinear processing is demonstrated on structures excited at their resonance frequency as well as out of resonance.
An upgrading of the 25 T cryogen-free superconducting magnet (CSM) at the HFLSM to a 30T-class CSM is considered by replacing the present Bi2223 insert coil with a REBCO ones, since REBCO tapes have ...better mechanical and in-field critical current properties. In our strategy for the REBCO coil of the 30T-CSM, two tapes co-winding technique will be adopted in order to increase the space current density in the coil and to avoid a hotspot generation due to local degradation. Electromagnetic and mechanical properties of two bundle co-wound (two-ply) pancake coils are investigated as an R&D test coil for the 30T-CSM. The R&D coils were fabricated with Fujikura REBCO tapes that have 4.1 mm width and 0.11 or 0.15 mm thickness depending on the coil. The coil voltages and strains were measured at 4.2 K under a background field of 11 T. The maximum hoop stress up to 460-530 MPa at the outermost winding estimated by the BJR relation was applied, and no degradation by the hoop stress was found.
This paper deals with the synchronized switch damping (SSD) technique, a semi-passive approach developed to address the problem of structural vibration damping. This technique takes advantage of an ...original nonlinear processing of the voltage generated by piezoelements. It was shown that the original control law for the SSD technique was optimal in the case of monomodal excitations. In the case of wide band multimodal excitation it is not true anymore. This paper proposes a novel multimodal control law for the SSD technique. It is based on a probabilistic description of the piezovoltage and results in an optimization of the energy dissipated in the nonlinear device connected to the piezoelectric elements.
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•Experimental evidence of wideband piezoelectric energy harvesting is given, with +200 % bandwidth compared to up-to-date solutions.•The ratio between the system bandwidth and the ...natural bandwidth of the transducer is 1017 %.•A strongly-coupled generator, specifically designed to that purpose, is presented.•An automatic procedure for maximum power point tracking is implemented for this innovative technique.•An analytical demonstration of the maximum power point is proposed and the main limitations are discussed.
This paper reports, for the first time, experimental evidence of the effectiveness of the frequency-tuning synchronized electrical charge extraction technique (FTSECE) with a strongly-coupled generator. The ratio between the system bandwidth (7 Hz) and the natural bandwidth of the transducer (0.688 Hz) is 1017 %, surpassing previous demonstrations of synchronized charge extraction methods by a large extent. We prove that the bandwidth of the FTSECE system is only limited by the unideal characteristics of the circuit components and generator. This is a major advantage of FTSECE as opposed to other competitive methods where the bandwidth is intrinsically mathematically limited, even in the hypothetical presence of ideal components. We also propose a new circuit for the implementation of FTSECE, which allows the piezoelectric generator to be connected to the same ground as the control circuit. Our experimental setup based on the combination of a strongly-coupled piezoelectric generator and a FTSECE architecture allows operation at a maximum power plateau on a +/-3.5 % interval around the resonance frequency. The resulting full width at half maximum (FWHM) is +/-10 % around the resonance frequency, which corresponds to +200 % compared to most up-to-date architectures designed for bandwidth enhancement, with the advantage of suppressing local minima in the power responses.
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