KEYWORDS: Composites, Bistability, Energy harvesting, Magnetism, Systems modeling, Microsoft Foundation Class Library, Resistors, Motion models, Manufacturing, Carbon
In this paper a bistable composite cantilever beam comprising asymmetric laminates is studied for vibration energy harvesting applications. An additional magnetic bistability is introduced to the harvesting system to lower the level of excitation that triggers the snap-through for the cantilever from one stable state to another, while retaining the favorable broadband performance. In order to achieve the, the cantilever beam is fitted with a permanent magnet at its tip that is oriented so that there is magnetic repulsion with a stationary magnet. The system performance can be adjusted by varying the separation between the magnets. Experimental results reveal that the use of magnetic bistability enhances broadband performance and improves the output power within a certain level of drive level and magnet separation. The load-deflection characteristic of the bistable beam is experimentally determined, and is subsequently used to model the system by a reduced single-degree-of-freedom (SDOF) system having the form of the Duffing equation for a double-well potential system. The dynamics of the beam are investigated using bifurcation diagrams and shows that the qualitative behavior given by the experimentally measured response is predicted well by the simple SDOF model.
In vibration-based energy harvesting, ambient vibration often occurs in such small amplitudes that it cannot be used to drive electrical generators directly. To maximize the amount of output power, the input motion is usually amplified before being used for power generation. This work presents a non-resonant piezoelectric energy harvester that relies on a compliant mechanism to amplify a given persistent input motion in order to enhance the power output. The device can be used in situations where a small cyclic relative motion occurs between two surfaces, and where a device can be fitted to extract energy. The use of a compliant mechanism, as opposed to conventional gear drives or linkages, alleviates problems of excessive clearances, friction and power losses. A finite element model is developed to investigate the effect of the various design parameters on the system performance in terms of the amplification ratio, stiffness and output voltage. Findings of the present work are verified both numerically and experimentally on a cam-driven polymer mechanism. A parametric study is conducted to investigate the most influential variables in an attempt to optimize the design parameters for maximum power output. A magnetically bistable piezoelectric beam, driven by the compliant mechanism, is finally presented and provides substantially greater amounts of output power.
Bistable systems have recently been employed for vibration energy harvesting owing to their favorable dynamic characteristics and desirable response for wideband excitation. In this paper, we investigate the use of bistable harvesters to extract energy from spinning wheels. The proposed harvester consists of a piezoelectric cantilever beam that is mounted on a rigid spinning hub and carries a tip mass in the form of a permanent magnet. Magnetic repulsion forces from an opposite magnet cause the beam to possess two stable equilibrium positions. Inter-well lead-lag oscillations caused by rotation in a vertical plane provide a good source for energy extraction. The design offers frequency tuning, as the centrifugal forces strain the harvester, thereby increasing its natural frequency to cope with a variable rotational speed. This has applications in self-powered sensors mounted on spinning wheels, such as tire pressure monitoring sensors. An effort is made to select the design parameters to enable the harvester to exhibit favorable inter-well oscillations across a range of rotational speeds for enhanced energy harvesting. Findings of the present work are verified both numerically and experimentally.
Conventional energy harvester consists of a cantilevered composite piezoelectric beam which has a proof
mass at its free end while its fixed end is mounted on a vibrating base structure. The resulting relative motion between
the proof mass and the base structure produces a mechanical strain in the piezoelectric elements which is converted
into electrical power by virtue of the direct piezoelectric effect. In this paper, the harvester is provided with a dynamic
magnifier consisting of a spring-mass system which is placed between the fixed end of the piezoelectric beam and the
vibrating base structure. The main function of the dynamic magnifier, as the name implies, is to magnify the strain
experienced by the piezoelectric elements in order to amplify the electrical power output of the harvester. With proper
selection of the design parameters of the magnifier, the harvested power can be significantly enhanced and the
effective bandwidth of the harvester can be improved. The theoretical performance of this class of Cantilevered
Piezoelectric Energy Harvesters with Dynamic Magnifier (CPEHDM) is developed using ANSYS finite element
analysis. The predictions of the model are validated experimentally and comparisons are presented to illustrate the
merits of the CPEHDM in comparison with the conventional piezoelectric energy harvesters (CPEH). The obtained
results demonstrate the feasibility of the CPEHDM as a simple and effective means for enhancing the magnitude and
spectral characteristics of CPEH.
Pipelines conveying gas under pressure exhibit turbulence-induced vibrations. The current work is concerned with
extracting useful power from pipelines operating well within their stability region. At such regions, the pipe vibrations exist in small magnitudes and are unlikely to cause structural failure, yet can be exploited to provide useful energy for low-power electronic devices. Accordingly, emphasis in the present work is placed on the development of an energy harvesting technique employing the omnipresent and inevitable flow-induced vibrations in gas pipelines.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.