scholarly journals Resonant Frequency Reduction of Piezoelectric Voltage Energy Harvester by Elastic Boundary Condition

2019 ◽  
Vol 35 (6) ◽  
pp. 779-793 ◽  
Author(s):  
Zhi Chao Ong ◽  
Yu-Hsi Huang ◽  
Sheng-Lun Chou
Keyword(s):  
Resonant Frequency ◽  
Natural Frequency ◽  
Energy Harvester ◽  
Real Life ◽  
Laser Doppler Vibrometer ◽  
Energy Output ◽  
Mode Shapes ◽  
Resonant Frequencies ◽  
Fundamental Natural Frequency ◽  
Piezoelectric Voltage

ABSTRACTMost vibration-based energy harvesters, including piezoelectric harvester system, perform efficiently at only its resonant frequency as linear resonators, usually at very high frequency which are out of the range of frequency of interest. In real life applications, these linear resonators are impractical since real ambient vibrations are simply having varying lower frequencies. Hence, design a tuneable vibration energy harvester at a lower and useful frequency range of interest are essential in allowing promising energy output to meet intended power input at a more practical approach. In this paper, the piezoelectric voltage energy harvester (PVEH) was designed with a flexible fixture with the aim to reduce its first fundamental natural frequency. Two thickness of elastic fixtures were applied to generate power on PVEH. Three experimental techniques were used to measure the vibration characteristics of PVEH. First, the full-field optical technique, amplitude-fluctuation electronic speckle pattern interferometry (AF-ESPI) measured simultaneously the resonant frequencies and mode shapes. This is followed by the pointwise measurement system, laser Doppler vibrometer (LDV) in which the resonant frequencies were measured by dynamic signal swept-sine analysis. The resonant frequencies and anti-resonant frequencies were also obtained by impedance analysis. The results obtained from experimental measurements were compared with finite element numerical calculation. It is found that the boundary conditions under the elastic fixtures can effectively reduce the resonant frequency of the PVEH with a reasonable voltage output. The fundamental natural frequency of PVEH with the thickness of 0.58-mm elastic fixture is reduced to 37 Hz maintaining at 7.1 volts (1.2 mW), in comparison with the natural frequency on cantilevered PVEH at 78 Hz that produces 7.7 volts (6.5 mW).

Maximizing the Fundamental Natural Frequency of Triangular Composite Plates

1996 ◽  
Vol 118 (2) ◽  
pp. 141-146 ◽  
Author(s):  
S. Abrate
Keyword(s):  
Natural Frequency ◽  
Material Properties ◽  
Composite Structures ◽  
Natural Frequencies ◽  
Ritz Method ◽  
Laminated Composite ◽  
Composite Plates ◽  
Mode Shapes ◽  
Fundamental Natural Frequency ◽  
Wide Range

While many advances were made in the analysis of composite structures, it is generally recognized that the design of composite structures must be studied further in order to take full advantage of the mechanical properties of these materials. This study is concerned with maximizing the fundamental natural frequency of triangular, symmetrically laminated composite plates. The natural frequencies and mode shapes of composite plates of general triangular planform are determined using the Rayleigh-Ritz method. The plate constitutive equations are written in terms of stiffness invariants and nondimensional lamination parameters. Point supports are introduced in the formulation using the method of Lagrange multipliers. This formulation allows studying the free vibration of a wide range of triangular composite plates with any support condition along the edges and point supports. The boundary conditions are enforced at a number of points along the boundary. The effects of geometry, material properties and lamination on the natural frequencies of the plate are investigated. With this stiffness invariant formulation, the effects of lamination are described by a finite number of parameters regardless of the number of plies in the laminate. We then determine the lay-up that will maximize the fundamental natural frequency of the plate. It is shown that the optimum design is relatively insensitive to the material properties for the commonly used material systems. Results are presented for several cases.

Heartbeat Energy Harvesting Using the Fan-Folded Piezoelectric Beam Geometry

2015 ◽  
Author(s):  
M. H. Ansari ◽  
M. Amin Karami
Keyword(s):  
Natural Frequency ◽  
Energy Harvester ◽  
Low Frequency ◽  
Mode Shapes ◽  
Vibration Energy ◽  
Vibration Energy Harvester ◽  
Mechanical Coupling ◽  
Energy Harvesters ◽  
Piezoelectric Energy ◽  
Piezoelectric Beam

A three dimensional piezoelectric vibration energy harvester is designed to generate electricity from heartbeat vibrations. The device consists of several bimorph piezoelectric beams stacked on top of each other. These horizontal bimorph beams are connected to each other by rigid vertical beams making a fan-folded geometry. One end of the design is clamped and the other end is free. One major problem in micro-scale piezoelectric energy harvesters is their high natural frequency. The same challenge is faced in development of a compact vibration energy harvester for the low frequency heartbeat vibrations. One way to decrease the natural frequency is to increase the length of the bimorph beam. This approach is not usually practical due to size limitations. By utilizing the fan-folded geometry, the natural frequency is decreased while the size constraints are observed. The required size limit of the energy harvester is 1 cm by 1 cm by 1 cm. In this paper, the natural frequencies and mode shapes of fan-folded energy harvesters are analytically derived. The electro-mechanical coupling has been included in the model for the piezoelectric beam. The design criteria for the device are discussed.

Postbuckling and Free Vibrations of Composite Beams

2007 ◽  
Author(s):  
Samir A. Emam ◽  
Ali H. Nayfeh
Keyword(s):  
Natural Frequency ◽  
Axial Load ◽  
Closed Form Solution ◽  
Composite Beams ◽  
Free Vibrations ◽  
Form Solution ◽  
Mode Shapes ◽  
Axial Stiffness ◽  
Fundamental Natural Frequency ◽  
Transverse Vibrations

An exact solution for the postbuckling configurations of composite beams is presented. The equations governing the axial and transverse vibrations of a composite laminated beam accounting for the midplane stretching are presented. The inplane inertia and damping are neglected, and hence the two equations are reduced to a single equation governing the transverse vibrations. This equation is a nonlinear fourth-order partial-integral differential equation. We find that the governing equation for the postbuckling of a symmetric or antisymmetric composite beam has the same form as that of a metallic beam. A closed-form solution for the postbuckling configurations due to a given axial load beyond the critical buckling load is obtained. We followed Nayfeh, Anderson, and Kreider and exactly solved the linear vibration problem around the first buckled configuration to obtain the fundamental natural frequencies and their corresponding mode shapes using different fiber orientations. Characteristic curves showing variations of the maximum static deflection and the fundamental natural frequency of postbuckling vibrations with the applied axial load for a variety of fiber orientations are presented. We find out that the line-up orientation of the laminate strongly affects the static buckled configuration and the fundamental natural frequency. The ratio of the axial stiffness to the bending stiffness is a crucial parameter in the analysis. This parameter can be used to help design and optimize the composite beams behavior in the postbuckling domain.

3D Modal Analysis of a Loaded Tire with Binary Random Noise Excitation

2019 ◽  
Vol 48 (3) ◽  
pp. 207-223
Author(s):  
Ipar Ferhat ◽  
Rodrigo Sarlo ◽  
Pablo A. Tarazaga
Keyword(s):  
Modal Analysis ◽  
High Frequency ◽  
Random Noise ◽  
Real Life ◽  
Laser Doppler Vibrometer ◽  
Static Condition ◽  
Three Dimensions ◽  
Vibration Measurement ◽  
Mode Shapes ◽  
Testing Techniques

ABSTRACT Modal analysis of tires has been a fundamental part of tire research aimed at capturing the dynamic behavior of a tire. An accurate expression of tire dynamics leads to an improved tire model and a more accurate prediction of tire behavior in real-life operations. Therefore, the main goal of this work is to improve the tire-testing techniques and data range to obtain the best experimental data possible using the current technology. With this goal in mind, we propose novel testing techniques such as piezoelectric excitation, high-frequency bandwidth data, and noncontact vibration measurement. High-frequency data enable us to capture the coupling between the wheel and tire as well as the coupling between airborne and structure-borne noise. Piezoelectric excitation eliminates the dynamic coupling of shakers and the inconsistency of force magnitude and direction of impact hammers as well as added mass effect. Noncontact vibration measurements using three-dimensional (3D) scanning laser Doppler vibrometer (SLDV) are superior to accelerometers because of no mass loading, a high number of measurement points in three dimensions, and high sensitivity. In this work, a modal analysis is carried out for a loaded tire in a static condition. Because of the highly damped nature of tires, multiple input excitation with binary random noise signal is used to increase the signal strength. Mode shapes of the tire are obtained and compared using both accelerometers and SLDV measurements.

Measurement and Visualization of Dynamics of Piezoelectric Microcantilever

2010 ◽  
Vol 437 ◽  
pp. 30-34
Author(s):  
Wei Jie Dong ◽  
Meng Wei Liu ◽  
Cui Yan
Keyword(s):  
Resonant Frequency ◽  
Optical System ◽  
Light Microscope ◽  
Vibration Mode ◽  
Ccd Camera ◽  
Mode Shapes ◽  
Micro Structure ◽  
Resonant Frequencies ◽  
Video Card ◽  
Piezoelectric Microcantilever

Methods for measuring the resonant frequencies and visualizing the motion of the Pb(Zr0.5Ti0.5)O3 microcantilever are investigated. Considering the two-segment structure of the microcantilever, a self-exiting self-sensing method is proposed to obtain the fundamental resonant frequency. An optical system consisting of light microscope, CCD camera and video card is established to visualize the first two vibration mode shapes. The theoretical, measured and visualized first resonance of one micocantilever is 17.28 kHz, 17 kHz and 17.8 kHz, respectively. A theoretical second resonance of 84.16 kHz is seen at 71.9 kHz. The proposed method is valid for measuring and visualizing low resonances of active micro structure.

Investigating the Feasibility of Tuning the Natural Frequency of an Electromagnetically-Transduced Energy Harvester Using Passively-Controlled Inductance

2014 ◽  
Author(s):  
Brennan E. Yamamoto ◽  
A. Zachary Trimble
Keyword(s):  
Energy Harvesting ◽  
Natural Frequency ◽  
Energy Harvester ◽  
Frequency Tuning ◽  
Excitation Frequency ◽  
Energy Output ◽  
Vibration Energy ◽  
Vibration Energy Harvesting ◽  
Mechanical Spring ◽  
Energy Harvesting System

As the required power for wireless, low-power sensor systems continues to decrease, the feasibility of a fully self-sustaining, onboard power supply, has increased interest in the field of vibration energy harvesting — where ambient kinetic energy is scavenged from the surrounding environment. Current literature has produced a number of harvesting techniques and transduction methods; however, they are all fundamentally similar in that, the harmonic excitation frequency must fall within the resonant bandwidth frequency of the harvesting mechanism to maintain acceptable energy output. The purpose of this research is to investigate the potential for natural frequency tuning by means of passive electrical components, that is, using an imposed electrical inductance to adjust the equivalent stiffness, and resulting resonant frequency of a vibration energy harvester. In past literature, it was concluded that an “active” frequency tuning mechanism would be infeasible, as the power required by an equivalent “stiffening transducer” would require more power to maintain the system at resonance, than the system would actually produce as a result of maintaining resonance, i.e., a net energy loss (Roundy and Zhang 2005). It is believed that the model used in this conclusion can be improved by directly modeling changes in system stiffness as an equivalent mechanical spring, instead of an external inertial loading. Due to the conservative nature of the harmonic spring, the compliance of a harvesting mechanism can be theoretically altered without energy losses, whether the actuation is applied using “active” or “passive” means. This revised model departs from the traditional, base excitation model in most vibration energy harvesting systems, and includes additional stiffness, and damping elements, representative of induced mechanical spring, and related losses. We can validate the feasibility of this technique, if it can be shown that the natural frequency of an energy harvester can be altered, and still maintain energy output similar to its “untuned” natural frequency. If feasible, this tuning method would provide a viable alternative to other bandwidth-increasing techniques in literature, e.g., wideband harvesting, bandwidth normalizing, high-damping, etc. In this research, a change in natural frequency of the experimental energy harvesting system of 0.5 Hz was demonstrated, indicating that adjusting the natural frequency of a vibration energy harvesting system is possible; however, there are many new challenges associated with the revised energy harvesting model, related to the new introduced losses to the system, as well as impedance matching between the mechanical and electrical domains. Further research is required to better quantitatively characterize the relationship between natural frequency shift, and imposed electrical inductance.

3D waviness effect of carbon nanotubes on fundamental natural frequency and modeling of resonance of nanocomposite structure

2021 ◽  
Author(s):  
Narendra Kumar Jha ◽  
Santosh Kumar ◽  
Srihari Dodla
Keyword(s):  
Carbon Nanotubes ◽  
Natural Frequency ◽  
Composite Beam ◽  
Volume Fraction ◽  
Mode Shapes ◽  
Fe Model ◽  
Vibratory System ◽  
Single Wave ◽  
Fundamental Natural Frequency ◽  
Neat Matrix

Optimum waviness of carbon nanotubes (CNTs) inside a matrix composite beam and composite bridge is endeavor to obtain its utmost natural frequencies considering a volume fraction of CNTs. 3D FE model of the beam is generated via ABAQUS along with Python programming and thereafter to calculate an optimal waviness under encastre boundary conditions and different vibration modes. The effect of waviness and the number of waves on mode shapes, natural frequency, and corresponding stiffness of a beam are examined, and the outcomes are compared to those of a pure polymer beam, straight CNT-based composite beam and nanobridge value. It was decided to conduct a convergence analysis and the optimum value of the number of elements and nodes was studied and found that 19666 nodes are reliable to give correct results. The FE analysis results reveal that the waviness effect of CNTs significantly depends on mode shapes. The fundamental natural frequency, as well as other related vibrational properties, is observed to be enhanced. By decreasing the waviness from 50 to 25, there is an increment in natural frequency in the 3rd mode by 68.68, 5th mode by 44.6 and 6th mode by 62.4, but in other modes, there is negligible difference. When single-wave CNTs were compared, the sine wave produced more frequency in the third mode by 206.03, 4th mode by 199.8 and 6th mode by 478.6[Formula: see text]Hz. After comparing the results of different waviness types, single sine waviness, multi-waved CNTs, straight CNTs and neat matrix, it is found that for the highest value of waviness of CNT fiber-based nanocomposites, the natural frequency of CNT-reinforced nanocomposite reaches the frequency of the neat matrix and further adding of CNTs does not increase the value of frequency. The result showed that the finite element model (FEM) is a good simulation of the vibratory system.

Energy Harvesting From Heartbeat Using Piezoelectric Beams With Fan-Folded Configuration and Added Tip Mass

2015 ◽  
Author(s):  
M. H. Ansari ◽  
M. Amin Karami
Keyword(s):  
Natural Frequency ◽  
Energy Harvester ◽  
Mode Shapes ◽  
Mechanical Coupling ◽  
Energy Harvesters ◽  
Piezoelectric Energy ◽  
Power Frequency ◽  
Tip Mass ◽  
Multi Mode ◽  
Very High

A fan-folded piezoelectric energy harvester is designed to generate electricity using heartbeat vibrations. This energy harvester consists of several bimorph beams stacked on top of each other making a fan-folded shape. Each beam has a brass substrate and two piezoelectric patches attached on both sides of it. These beams are connected to each other by rigid beams. One end of the device is clamped to the wall and the other end is free to vibrate. A tip mass is placed at the free end to enhance the output power of the device and reduce the natural frequency of the system. High natural frequency is one major concern about the microscaled energy harvesters. The size for this energy harvester is 1 cm by 1 cm by 1 cm, which makes the natural frequency very high. By utilizing the fan-folded geometry and adding tip mass and link mass to the configuration, this natural frequency is reduced to the desired range. The generated electricity can be used to power up a pacemaker. If enough electricity is generated, the pacemaker operates without having a battery and the patient does not need to have a surgery every seven to ten years to have the battery replaced. The power needed for a pacemaker to operate is about 1 microwatt. In this paper, the natural frequencies and mode shapes of fan-folded energy harvesters with added tip mass and link mass are analytically derived. The electro-mechanical coupling has been included in the model and the expression for the multi-mode power frequency response function is calculated.

Nonlinear Thermally Buckled Piezoelectric Energy Harvester

2016 ◽  
Author(s):  
M. H. Ansari ◽  
M. Amin Karami
Keyword(s):  
Natural Frequency ◽  
Energy Harvester ◽  
Microelectromechanical Systems ◽  
Energy Content ◽  
The Body ◽  
Mode Shapes ◽  
Governing Equations ◽  
Biomedical Sensors ◽  
Piezoelectric Energy ◽  
Bimorph Beam

A thermally buckled piezoelectric energy harvester is designed to power biomedical devices inside the body. The energy harvester (EN) uses the vibrations inside the body to generate the electricity needed for powering biomedical sensors and devices. The piezoelectric beam consists of a brass substrate and two piezoelectric patches attached to the top and the bottom of the substrate. The bimorph beam is inside a rigid frame. The bimorph beam is buckled due to the difference in the coefficient of the thermal expansion of the beam and the frame. Inside the body, most of the energy content come from the low-frequency vibrations (less than 50 Hz). Having high natural frequency is a major problem in Microelectromechanical systems (MEMS) energy harvesters. Considering the small size of the EN, 1 cm3, the natural frequency is expected to be high. In our design, the natural frequency is lowered significantly by using a buckled beam. A mass is also used in the middle of the beam to decrease the natural frequency even more. Since the beam is buckled, the design is bistable and nonlinear which increases the output power. In this paper, the natural frequencies and mode shapes of the EN are analytically derived. The geometric nonlinearities are included in the electromechanical coupled governing equations. The governing equations are solved and it is shown that the device generates sufficient electricity to power biomedical sensors and devices inside the human body.

Frequency Sweep Test and Modal Analysis of Watermelon during Transportation

2017 ◽  
Vol 13 (5) ◽  
Author(s):  
Fang Wang ◽  
Shaochun Ma ◽  
Wei Wei ◽  
Yong Zhang ◽  
Ziyi Zhang
Keyword(s):  
Resonant Frequency ◽  
Resonance Frequency ◽  
Modal Analysis ◽  
Natural Frequency ◽  
Natural Frequencies ◽  
Mode Shapes ◽  
Frequency Range ◽  
Frequency Sweep ◽  
Order Resonance ◽  
Frequency Sweep Test

Abstract Determining the natural frequency of watermelon is important to reduce loss by vibration during transportation. The purpose of frequency sweep test is to determine the tolerance of watermelon to vibration within a certain frequency range and to search the resonant frequency of watermelon in a certain frequency range. Frequency sweep test of Xinong No.8 watermelon cultivar was conducted, and the acceleration transmissibility curve was obtained. Furthermore, the 1st and 2nd order natural frequencies of watermelon were determined as 35.125 Hz and 71.034 Hz respectively from the acceleration transmissibility curve. Based on Geometric and mechanical parameters of Xinong No.8 watermelon cultivar, a finite element analysis model was developed and modal analysis of watermelon was carried out to obtain its natural frequencies and mode shapes. Since the value of 1st and 2nd order resonance frequency were the same or similar to the value of 3rd, 4th, and 5th order resonance frequency, this study only focused on 1st and 2nd order modes. The 1st order and 2nd order natural frequency test data fit to the corresponding simulation data well which validated the FEA model. This study demonstrated the feasibility of detecting the resonant frequency of watermelon vibration during transportation using FEA methods and provided a theoretical basis for watermelon transportation device design to reduce damage by avoiding resonant frequency.

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