Search

This article focuses on an intelligent control strategy to improve the performances of shunt-rectifier architectures for vibration energy harvesting. It demonstrates how proper tuning can improve the frequency bandwidth and maximum power of unipolar synchronized electric charge extraction architectures. For resonators with strong enough coupling (k 2 Q > π / 2), tuning the duration of charge extraction with the oscillation frequency improves the power harvesting performances. The main differences with other similar solutions such as unipolar synchronized electric charge extraction without tuning strategy or tunable synchronized electric charge extraction are illustrated. In particular, we show how the choice of the shunt rectifier significantly affects the power response of the generator due to electromechanical coupling phenomenon. The analytical study is experimentally validated on a cantilever-based piezoelectric generator. [ABSTRACT FROM AUTHOR]

This article presents a new way to control the synchronous electric charge extraction interface circuit, which was formerly developed to improve the performances of piezoelectric vibration energy harvesting devices. An analytical model for energy harvesting systems including this new technique, called phase-shift synchronous electric charge extraction, is proposed. This model is then used to study the properties of this new control scheme in the cases of low and high electromechanical coupling. Contrary to the synchronous electric charge extraction technique which exhibited significant improvements in terms of harvested power for piezoelectric devices with low electromechanical coupling, the phase-shift synchronous electric charge extraction technique shows capability to increase the harvested power up to the theoretical limit for piezoelectric devices with high electromechanical coupling. In addition, the presented theoretical results show that the frequency bandwidth of piezoelectric energy harvesting devices may be substantially increased. [ABSTRACT FROM AUTHOR]

This study investigates the feasibility of heat energy harvesting using pyroelectric effect. In order to improve the effectiveness of the energy conversion from heat to electricity, the synchronized switch harvesting on inductor (SSHI) (Guyomar et al., 2005) technique is experimentally tested, which has already proved its quality in electromechanical conversion. For several amplitude variations of temperature from 0.5 to 8.0 K, the conversion efficiency is found about 0.02% of Carnot thermodynamic cycle with a standard interface. Under the same heating conditions, experimental results show that the SSHI technique increases the converted energy by a factor which is about 2.5 times of the standard interface, with which the efficiency practically becomes 0.05% of Carnot thermodynamic cycle. In this case, the produced electrical power for temperature amplitude 7K is more than 0.3mW for an energy harvesting device composed of 8 g of active material. The main power limitation is due to temperature frequency. Low speed of heat transfer makes it difficult to obtain fast temperature variations with large amplitude. [ABSTRACT FROM AUTHOR]

This article is focused on the problem of vibration control for Printed Circuit Boards (PCBs). The proposed control is based on a semi-passive technique called Synchronized Switch Damping on Inductor (SSDI). Implementation of this technique requires PZT inserts and only a few electronic components. Since no external source provides electrical energy to the inserts, a relatively important electromechanical coupling factor is needed to get significant vibration damping. Moreover, the PCB surface that can be covered by the PZT inserts is restricted, limiting the global coupling factor. Optimal location and geometry of the active material are determined according to these constraints using Finite Element Modelling (FEM) of the structure. Experimental results exhibit 15 dB and 10 dB attenuations for the first and the third bending modes respectively. These results are in good agreement with the theoretical predictions. Transient vibration decay is more than 4 times faster. These promising results show that the SSDI technique provides effective protection of PCBs against shocks and vibrations, while the system is lighter than active controls and more robust than passive controls. [ABSTRACT FROM AUTHOR]

This article describes a new approach to harvest electrical energy from a mechanically excited structure equipped with piezoelectric elements. Standard harvesting circuits using piezoelectric elements as an electric generator consist of an AC-DC converter coupled to a load. The technique proposed herein is fully compatible with the standard approach. The difference consists in adding up an electrical switching device connected in parallel with the piezoelectric elements. The switch device is triggered on the maxima or minima of the displacement and realizes a voltage inversion through an inductor. This method allows the artificial increase of the piezoelements' output voltage, resulting in a significant increase of the electrical power flow. It is shown that the power flow transfer strongly depends on the structure electromechanical coupling coefficient. For a weakly coupled structure using this new technique, the electrical power can be increased by over 400% [ABSTRACT FROM AUTHOR]

Semi-passive damping techniques have been developed recently to address the problem of structural damping. Contrary to the standard passive piezoelectric damping, these new techniques adapt to environmental variations. Moreover, they present interesting multimodal damping performances. However, their efficiency is strongly correlated with their electromechanical coupling. The enhanced semi-passive damping technique presented herein compensates for this drawback. It reinforces the electromechanical coupling by artificially increasing the voltage amplitude delivered by the piezoelectric patches. Theoretical predictions and experimental results show a - 24 dB attenuation on the vibration of a resonant cantilever steel beam, while reducing the piezoelectric material volume by 83%. [ABSTRACT FROM AUTHOR]

This article presents a nonlinear approach to optimize the power flow of vibration-based piezoelectric energy-harvesting devices. This self-adaptive principle is based on a particular synchronization between extraction of the electric charge produced by the piezoelectric element and the system vibrations, which maximizes the mechanical to electrical energy conversion. An analytical expression of the optimal power flow is derived from a simple electromechanical model. An electronic circuit designed to perform the synchronous charge extraction is proposed. Theoretical predictions confirmed by experimental results show that the new principle increases the harvested power by 400% as compared with a quasilinear impedance adaptation optimization method. [ABSTRACT FROM AUTHOR]