622 research outputs found
Investigation of electrical properties for cantilever-based piezoelectric energy harvester
In the present era, the renewable sources of energy, e.g., piezoelectric materials are in great demand. They play a vital role in the field of micro-electromechanical systems, e.g., sensors and actuators. The cantilever-based piezoelectric energy harvesters are very popular because of their high performance and utilization. In this research-work, an energy harvester model based on a cantilever beam with bimorph PZT-5A, having a substrate layer of structural steel, was presented. The proposed energy scavenging system, designed in COMSOL Multiphysics, was applied to analyze the electrical output as a function of excitation frequencies, load resistances and accelerations. Analytical modeling was employed to measure the output voltage and power under pre-defined conditions of acceleration and load resistance. Experimentation was also performed to determine the relationship between independent and output parameters. Energy harvester is capable of producing the maximum power of 1.16 mW at a resonant frequency of 71 Hz under 1g acceleration, having load resistance of 12 k Omega. It was observed that acceleration and output power are directly proportional to each other. Moreover, the investigation conveys that the experimental results are in good agreement with the numerical results. The maximum error obtained between the experimental and numerical investigation was found to equal 4.3%
Numerical modeling of shape and topology optimisation of a piezoelectric cantilever beam in an energy-harvesting sensor
Piezoelectric materials are excellent transducers for converting mechanical energy from the environment for use as electrical energy. The conversion of mechanical energy to electrical energy is a key component in the development of self-powered devices, especially enabling technology for wireless sensor networks. This paper proposes an alternative method for predicting the power output of a bimorph cantilever beam using a finite-element method for both static and dynamic frequency analyses. A novel approach is presented for optimising the cantilever beam, by which the power density is maximised and the structural volume is minimised simultaneously. A two-stage optimisation is performed, i.e., a shape optimisation and then a “topology” hole opening optimisation
Electrostrictive Polymers for Mechanical-to-Electrical Energy Harvesting
Research of electrostrictive polymers has generated new opportunities for harvesting energy from the surrounding environment and converting it into usable electrical energy. Piezoelectric ceramic based devices have long been used in energy harvesting for converting mechanical motion to electrical energy. Nevertheless, those materials tend to be unsuitable for low-frequency mechanical excitations such as human movement. Since organic polymers are typically softer and more flexible, the translated electrical energy output is considerably higher under the same mechanical force. Currently, investigations in using electroactive polymers for energy harvesting, and mechanical-to-electrical energy conversion, are beginning to show potential for this application. In this paper we discuss methods of energy harvesting using membrane structures and various methods used to convert it into usable energy. Since polymers are typically used in capacitive energy harvesting designs, the uses of polymer materials with large relative permittivities have demonstrated success for mechanical to electrical energy conversion. Further investigations will be used to identify suitable micro-electro mechanical systems (MEMs) structures given specific types of low-frequency mechanical excitations (10-100Hz)
PVDF-TrFE Electroactive Polymer Mechanical-to-Electrical Energy Harvesting Experimental Bimorph Structure
Research of electrostrictive polymers has generated new opportunities for harvesting energy from the surrounding environment and converting it into usable electrical energy. Electroactive polymer (EAP) research is one of the new opportunities for harvesting energy from the natural environment and converting it into usable electrical energy. Piezoelectric ceramic based energy harvesting devices tend to be unsuitable for low-frequency mechanical excitations such as human movement. Organic polymers are typically softer and more flexible therefore translated electrical energy output is considerably higher under the same mechanical force. In addition, cantilever geometry is one of the most used structures in piezoelectric energy harvesters, especially for mechanical energy harvesting from vibrations. In order to further lower the resonance frequency of the cantilever microstructure, a proof mass can be attached to the free end of the cantilever. Mechanical analysis of an experimental bimorph structure was provided and led to key design rules for post-processing steps to control the performance of the energy harvester. In this work, methods of materials processing and the mechanical to electrical conversion of vibrational energy into usable energy were investigated. Materials such as polyvinyledenedifluoridetetra-fluoroethylene P(VDF-TrFE) copolymer films (1um thick or less) were evaluated and presented a large relative permittivity and greater piezoelectric β-phase without stretching. Further investigations will be used to identify suitable micro-electromechanical systems (MEMs) structures given specific types of low-frequency mechanical excitations (10-100Hz)
Plucked piezoelectric bimorphs for knee-joint energy harvesting: modelling and experimental validation
The modern drive towards mobility and wireless devices is motivating intensive
research in energy harvesting technologies. To reduce the battery burden on
people, we propose the adoption of a frequency up-conversion strategy for a new
piezoelectric wearable energy harvester. Frequency up-conversion increases
efficiency because the piezoelectric devices are permitted to vibrate at
resonance even if the input excitation occurs at much lower frequency.
Mechanical plucking-based frequency up-conversion is obtained by deflecting the
piezoelectric bimorph via a plectrum, then rapidly releasing it so that it can
vibrate unhindered; during the following oscillatory cycles, part of the
mechanical energy is converted into electrical energy. In order to guide the
design of such a harvester, we have modelled with finite element methods the
response and power generation of a piezoelectric bimorph while it is plucked.
The model permits the analysis of the effects of the speed of deflection as well
as the prediction of the energy produced and its dependence on the electrical
load. An experimental rig has been set up to observe the response of the bimorph
in the harvester. A PZT-5H bimorph was used for the experiments. Measurements of
tip velocity, voltage output and energy dissipated across a resistor are
reported. Comparisons of the experimental results with the model predictions are
very successful and prove the validity of the model
Model and design of a double frequency piezoelectric resonator
A novel design of a multifrequency mechanical resonator with piezoelectric materials for energy harvesting is presented. The electromechanical response is described by a finite element model, which predicts the output voltage and the generated powe
Employee attitudes as a mediator between HRM and organizational performance
Attitude is a power that controls human behaviour. When employee Attitude is positive, it can give impact positive to organization performance. A proper human resource management (HRM) managed by organization, the employee attitude will be affected. HRM practices influence employee attitude positively and there is a mediating role of employee attitude between training and development dimension of HRM practices and organizational performance. Therefore, the purpose of this study is to explore employee atttiude as a mediator between HRM and organizational performance. A sample of this study was 219 respondents from employee construction in Libya. The data was analyzed using structural equation modelling (SEM) approach. This study showed that employee attitudes is a full mediator between relationship HRM and organizational performance. Therefore, HRM practices influence employee attitude and its give impact to organizational performance for more effective and efficient in achieving organization goal
Modeling and Analysis of Bimorph Piezoelectromagnetic Energy Harvester
Piezoelectric energy harvesting is one of the methods of obtaining energy from environment. It is often a cantilever beam with or without tip mass poled with piezoelectric material. The fixed end of cantilever beam is subjected to either base excitation or translation as occurring from an environmental source such as automobile or vibrating engine. The piezoelectric energy harvester generates maximum energy when it is excited at resonance frequency and the little variation below or above the resonance frequency will drastically reduce the power output. In this line, present work studies a broadband nonlinear piezoelectric energy harvester driven by periodic and random oscillations. The simulated response to the base excitation is illustrated in terms of harvested power. By introducing magnetic force, we can broaden the frequency zone so as to capture more energy even the beam do not vibrate close to source frequency. A magnetic tip is included at the free end of the cantilever beam and is excited by two permanent magnets fixed on either sides laterally. The symmetric bimorph cantilever beam piezoelectric energy harvester with magnetic tip is modeled as Single-degree of freedom lumped parameter system. The time domain history and frequency response diagrams for the cantilever displacement, voltage and power at the constant load resistance gives a stability picture as well as the amount of energy harvested. The effect of various parameters of energy harvester system on induced voltage and output power is studied. The distributed parameter model is formulated by using Euler-Bernoulli beam theory and Galerkin’s approximation technique. The finite element modeling equations are presented with piezoelectric coupling terms. Novelty in the work include; (i) adding a magnetic force in the system to make it as broadband harvester (ii) validation of approximation solutions with spring-mass modeling
DEVELOPMENT OF PIEZOELECTRIC ENERGY HARVESTING SYSTEM FOR LOW-FREQUENCY VIBRATIONS
Harvesting energy from vibration sources has attracted the interest of researchers for the past three decades. Researchers have been working on the potential of achieving self-powered MEMS scale devices. Piezoelectric cantilever harvesters have caught the attention in this field because of the excellent combination of high-power density and compact structure. The main objective of this thesis is to develop a novel and optimum piezoelectric harvester system using lumped parameter model (LPM) for given vibration sources. The finite element model (FEM) is used in this work as an original approach to be utilized for optimal design optimization. Three types of validations are accomplished to solidify the use of FEM in mimicking the distributed parameter model (DPM) for linearly tapered piezoelectric cantilevers. The first two validations are accomplished using beam deflection and relative transmissibility functions. Comparisons between the FEM and the DPM developed by the literature are performed. The third validation is carried for an electromechanical piezoelectric cantilever in FEM. Results confirmed the effectiveness of the developed FEM. A number of significant contributions are achieved while fulfilling the aim of this work. First, a dimensionless parameter, Power Factor (PF), is derived and used to understand the impact of the geometry on the piezoelectric harvester performance. The PF showed an optimum performance at a taper ratio of 0, taking the full length of the cantilever and thickness ratio of 0.7. Second, the accuracy of the LPM for linearly tapered piezoelectric harvesters and optimal design are investigated. Results indicated that the percentage of the deflection error between the LPM and the FEM reaches 9% when the taper ratio is zero. However, when tip-mass to cantilever ratios are larger than 2, the error decreases to less than 0.5% leading to more accurate results in the vibrational response of the beam. Further studies on the accuracy are accomplished using the relative transmissibility function. Results showed that as the taper ratio decreases towards zero, the percentage error of using the LPM to predict the vibration response increases significantly to 55%. These results lay the foundation for the third contribution of developing correction factors for tapered and optimal piezoelectric cantilever harvesters using FEM. Comparisons of the corrected LPM and FEM for different configurations are examined. Results indicated that as the taper ratio decreases, the surface power density increases. However, the developed optimal design exhibits the highest surface power density of 1.40×104 [(mW/g2)/ m2] which is 16.4% more than the best following shape of a taper ratio 0.2 and 58% more than the taper ratio 1. Furthermore, a parametric study of the optimal design is performed to scrutinize the effect of various parameters on the harvester performance. Finally, detailed criteria for designing the optimal piezoelectric harvester for different conditions are structured
DESIGN, MODELING AND CHARACTERIZATION OF A PIEZOELECTRIC ENERGY HARVESTING DEVICE
The mechanical vibratory energy has been extracted based on the car engine’s frequency and converted into an electrical energy by making use of a bimorph piezoelectric harvesting device; this process is called energy harvesting. The output of that energy used to power-up small electronics devices such as electronic transmitters and sensors which utilize low voltage and current (1-5 Volt / 10 - 20 mA). A cantilever of Lead-Zirconate-Titanate (PbZrO3TiO2) with dimensions of (40 × 10 ×
0.5 mm) has been analyzed and it’s produced an output power in the range of (100μW - 0.4mW) at resonance frequency of (≤ 0.2 KHz) under peak acceleration of (≤ 10 m/s2). This cantilever’s targeted vibration is dynamic (damped) vibration; therefore it has been subjected into continuous vibratory force. The Static Vibration is run at the first stages to check the working force and stamina of the cantilever by applying a pulse of movement and observe the response of the transient wave of the cantilever. The project aims to design and model a bimorph piezoelectric (PZT) cantilever device uses the effects of piezoelectric property to extract the mechanical vibration that is generated based on the car engine compartment’s specifications and convert it to electrical energy. Successfully, a bimorph piezoelectric harvester cantilever was designed under the optimal conditions identified in this report to extract the car engine vibration produced by dynamic vibration shaker using the typical frequencies and acceleration of the car engine and produced output power nearly 0.39 mW when converts this extracted vibration to electrical energ
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