Low Ambient Vibrations Research Articles

Noncontact magnetically coupled piezo-electromagnetic rotary energy harvester

Aiming at the problems of high environmental vibration frequency, low output power and short life of the energy harvesters, a noncontact magnetically coupled piezo-electromagnetic rotary energy harvester is proposed in this paper. It consists of a base, a top cover, a rotating body, a cantilever beam, a permanent magnet, a coil, a hollow tube and a clamp. The novel hybrid harvester can produce both piezoelectric and electromagnetic energy at the same time, and in addition, it can efficiently generate electricity at low ambient vibration. Moreover, the piezoelectric material is protected from direct collision by noncontact magnetic coupling excitation. In order to conduct a comprehensive study on the performance of the piezoelectric-electromagnetic rotary energy harvester, we set up a rotating test platform to carry out systematic test verification, and to determine the distance between the permanent magnet and the rotating body and the number of permanent magnets on the rotating body. The test results show that when four permanent magnets are uniformly pasted on the rotating body and the rotating speed is 775 r/min, the piezoelectric and electromagnetic output power are 3.4 mW and 2.69 mW, respectively, and the total hybrid output power is 6.09 mW.

Multiple spring-mass oscillator for wide bandwidth piezoelectric energy harvester

This work proposed a design of unique wideband piezoelectric energy harvester. The solution toward broadband response was achieved by using multiple spring-mass oscillators integrated with piezoelectric energy harvester array. The harvester was demonstrated to harvest continuous power from vibration source under various frequencies in the range of 0-250 Hz. It is shown that the stable output power of the harvester over a wide range of source frequency was achieved. The maximum output voltage and power of each beam were 4, 3.6, 9.8, 10 V and 0.01, 0.07, 0.45, 0.52 mW for 15, 30, 45 gm of the proof masses and the superimposed case, respectively. The resonant frequencies of the harvester were in the low ambient vibration frequency range. Expanded in resonance frequency was achieved in this new design harvester.

Cascaded essential nonlinearities for enhanced vibration suppression and energy harvesting

The concept of simultaneous energy harvesting and vibration suppression has made tremendous progress in the past few years. However, the energy harvesting and vibration reduction seem to be independent, or even paradox in some scenarios; for example, energy harvesting strategy expects the primary system to maintain large-amplitude vibration as long as possible. In comparison, the vibration suppression strategy aims to suppress the vibration of primary system as soon as possible. In this paper, we aim to demonstrate how to properly design an integrated system, which first ensures the broadband vibration suppression performance, while at the same time, harvests additional energy as much as possible. To achieve this goal, a cascaded essentially nonlinear system is presented for high-sensitive vibration and harvesting energy. The presented device comprises a nonlinear energy sink and a nonlinear energy harvester with cascaded essential nonlinearities. Numerical results show that the presented device is able to simultaneously suppress vibration and harvest vibration energy over a wide frequency range. Moreover, unlike previous research, it is effective for extremely small initial impulses. This work explores possibilities for reducing and harvesting extremely low ambient vibration.

Triboelectricity-based self-charging droplet capacitor for harvesting low-level ambient energy

Abstract In this study, we propose a self-charging droplet capacitor for harvesting low-level mechanical energy. The capacitor comprises of a conductive liquid droplet, which is placed on a heterogeneous and hydrophobic surface of dielectric materials coated onto a conductive substrate. The substrate and the droplet, along with the dielectric materials in between, form a parallel-plate type capacitor. The droplet is free to move on the surface, and thus, enables the position-dependent variation of capacitance. The surface consists of two regions, each with a different material and thickness. The different strengths of solid-water contact electrification of the two materials give rise to a self-charging mechanism. The variation in thickness allows for the capacitance change required for energy harvesting. A device is fabricated with two droplet capacitors and one ceramic capacitor. Passive diode switches are used to enable reconfiguration of the connectivity of the capacitors, which leads to a geometrical growth of the energy in the system. With a 450 μL water drop in each capacitor, the device can effectively harvest energy from low ambient vibrations. The energy harvested grows by 100 times within 11 cycles, sufficient to illuminate 30 LEDs connected in series.

Fundamentals of roller integrated compaction control for oscillatory rollers and comparison with conventional testing methods

Abstract Oscillatory rollers are used for compaction work in sensitive areas like inner city construction sites or near vibration-sensitive structures due to their ability to cause very low ambient vibrations. The fundamentals of oscillatory roller compaction and Continuous Compaction Control (CCC) with oscillatory rollers are discussed within the present paper. The influence of the soil stiffness on the motion behaviour of an oscillatory drum was studied to introduce a novel CCC value for oscillatory rollers based on these findings. The algorithm for the calculation of this novel CCC value for oscillatory rollers is tested on real acceleration measurements obtained from experimental field tests. Moreover, the CCC value is extensively compared to the results of dynamic load plate test by means of the Light Falling Weight Device and to the results of CCC measurements with vibratory rollers.

Design and experiment of piezoelectric multimodal energy harvester for low frequency vibration

Abstract Most piezoelectric vibration energy harvesters are conventional single-degree-of-freedom (SDOF) systems, and typically perform well at the single resonant mode - which makes the harvesters less efficient for low ambient vibration frequencies. In this work, we have proposed and experimentally validated a piezoelectric multimodal energy harvester having several mechanical degrees of freedom (DOFs). This multi-modal vibration energy harvester has a unique design that helps to obtain multiple resonant mode operation of the harvester at the lower frequency range. The finite element method (FEM) simulation model has been used to predict the mode shapes of the proposed energy harvester at different vibration modes. The experimental results imply that the proposed energy harvester can obtain four peak values in the range of 10–20 Hz, which are concentrated around 10, 14, 16, and 20 Hz respectively. In addition, the piezoceramic material lead zirconate titanate (PZT) has been used as a piezoelectric element that has excellent piezoelectric properties. A prototype multimodal energy harvester with four piezoelectric elements is fabricated, where a single piezoelectric element generated a peak power with a maximum of 249 µW delivered to an optimum load of 55 KΩ at 16 Hz resonant mode under 0.4 g base acceleration. In order to increase the output power and bandwidth, it is always a good idea to use multiple piezoelectric elements in one harvester structure; consequently, four piezoelectric elements of the fabricated prototype are connected in parallel. The device with parallel connected piezoelectric modules generates a peak output power of 740 µW across an equivalent optimum load resistance at 3rd resonant mode (16 Hz), while the device's base is excited at 0.4 g acceleration.

Simulation and Characterisation of Planar Spring Based on PCB-FR4 in Electromechanical System for Energy Harvesting

This paper presents comparison study of simulation and fabrication characterized two type planar springs at micro–fabricated electromagnetic power generator for an ambient vibration energy harvesting system. The power generator utilized a LASER–machined FR4-PCB planar spring, a copper coil, and NdFeB magnet. In order to change resonant frequency, we developed a gimbal suspension structure for the fabrication of spring. The NdFeB permanent magnet was applied as inertial mass. The system was specially designed to harvest low ambient vibrations from 20 to several hundred hertz and low acceleration. The dimension of fabricated energy harvester had 2.5 x 2.5 cm2 in size. In this study we present two different design of cantilever, which is has two and four cantilever, respectively. The different designed given different resonance frequency to the system. The result of simulation giving resonance frequency of two cantilever membrane 22.6 Hz and four cantilever membrane 110.3 Hz. The measurements result has generated 0.135 V with resonance frequency 39 Hz of two cantilever membrane appropriate for human motions, four cantilever membrane has generated 0.174 V with resonance frequency106 Hz appropriate for machine industries.

Electromagnetic Energy Harvester for Low Frequency Vibrations Using MEMS

This paper proposes design and analysis of electromagnetic energy harvester using MEMS technology. The energy harvester is intended to harvest energy from low frequency ambient vibrations that is less than 100Hz. The design would consist of a cantilever which is the simplest MEMS structure which can further be used to power the amplifiers. These amplifiers can be used to amplify the low amplitude and low frequency vibration signals. The work intends to explore the opportunities in harnessing vibrations induced by the live loads, such as laden Lorries & Buses on bridges, to harvest energy in the form of generated voltage. A cantilever based electromagnetic energy harvester can be employed to capture these miniscule level of vibrations and convert them into electrical energy. The Faraday's law of electromagnetic induction is the fundament idea utilized to design the cantilever beam simulated with dimensions of 2500x500μm. The material plays a vital role in sensitivity and hence NdFeB is selected as magnetic material whereas Aluminum as the conducting coil electrode material. The voltage of 2.34mV is generated using single cantilever beam energy harvester. An array of six such cantilevers generates a voltage of 3.27mV. The simulation results confirm that the low ambient vibrations can be effectively utilized to generate useful energy.

Low frequency piezoelectric energy harvesting at multi vibration mode shapes

A multi-degree of freedom micro-energy harvester has been designed, fabricated, and tested and sub 100Hz natural frequencies have been achieved. This design's resonant frequencies at its first three mode shapes are within the low ambient vibration frequency range. The structure is fabricated from a silicon substrate with Aluminum Nitride (AlN) energy harvesting elements on thin silicon beams and uses a chip as a proof mass. The nonlinear stiffness due to stretching strain in the structure provides a wider harvestable frequency bandwidth in each mode. The nonlinear load-deflection equation for the second mode shape of the device, which corresponds to vertical oscillation and maximum harvester deflection, has been modeled using finite element simulation. The first three natural frequencies of 71.8, 84.5, and 188.4Hz were measured experimentally for the presented harvester. A frequency bandwidth of 10Hz has been obtained for the second mode shape under a base excitation of 0.2g. A maximum open circuit voltage of 1V and power output of 136nW with a load resistance of 2MΩ have been measured using this harvester. Using a synchronized switch harvesting on inductor (SSHI) electrical interface and Lead Zirconate Titanate (PZT), simulations estimate that the power output could be improved to ∼3.1μW.

Seismic characterization of rigid sites in the ITACA database by ambient vibration monitoring and geological surveys

The problem of seismic characterization of rock-mass or stiff-soil outcrops by the use of passive seismic prospecting techniques is discussed. Difficulties in the application of this kind of procedure in the presence of rugged morphology, high surface wave velocities and low ambient vibration powers, typical of stiff-soil/rock-mass sites are examined. A methodology to face these problems is here proposed, which is based on the strict synergy of detailed geologic surveys and application of robust seismic prospecting techniques, jointly considering single-station and multi-station tools. The application of this approach for the characterization of a number of sites belonging to the Italian Accelerometric Network is described, focusing on two representative case histories.

A Bulk Micromachined Electromagnetic Micro-Power Generator for an Ambient Vibration-energy-harvesting System

This paper presents a micro-fabricated electromagnetic power generator for an ambient vibration energy harvesting system. The proposed power generator utilized a bulk micro-machined silicon spring, a copper coil, and NdFeB magnet. In order to reduce the resonant frequency and increase the displacement of the proof mass, we developed a gimbal suspension structure for the fabrication of the silicon spring. The NdFeB permanent magnet was applied as an inertial mass to increase the effective mass of the total spring system. The fabricated spring was assembled using a lowcost Polydimethylsiloxane (PDMS) packaging substrate with a micro-coil, which had a lower DC resistance than a micro-fabricated planar coil. The system was specially designed to scavenge low ambient vibrations of several tens of hertz and low accelerations of under 1 g. The fabricated energy harvester had a 1 × 1 × 0.6 cm size and generated 102 μW of electrical power to a 100 Ω load at 201 mVpeak-to-peak from a vibration of 0.4 g at 53 Hz. The normalized power density was 1.06 mW/cm·g.

Micro-Fabricated Electromagnetic Power Generator to Scavenge Low Ambient Vibration

In this paper, micro-fabricated electromagnetic power generator is presented to convert the low level ambient vibration into electric energy. The proposed micro-power generator is comprised of three micro-components such as bulk-micromachined silicon spiral spring, low loss copper micro-coil, and NdFeB magnet to be assembled with low cost PDMS packaging substrate. In order to maximize the output power, magnet is applied as inertial mass at the center of silicon spiral spring to adjust its resonant frequency. Especially, NdFeB discrete/miniaturized magnet and copper wire wounded micro-coil were utilized to avoid the performance deterioration of the proposed device due to its miniaturization. It was specially designed for scavenging low ambient vibration of several tens of hertz and low acceleration under 1g. The fabricated device generated output power of 115.1 W and load voltage of 68.2 mV to the load resistance of 18.1 from the vibration of 54 Hz with acceleration of 0.57 g. The normalized power density was 590.4 ?W/cm3g2.

A micro electromagnetic low level vibration energy harvester based on MEMS technology

This paper presents a micro electromagnetic energy harvester which can convert low level vibration energy to electrical power. It mainly consists of an electroplated copper planar spring, a permanent magnet and a copper planar coil with high aspect ratio. Mechanical simulation shows that the natural frequency of the magnet-spring system is 94.5 Hz. The resonant vibration amplitude of the magnet is 259.1 μm when the input vibration amplitude is 14 μm and the magnet-spring system is at resonance. Electromagnetic simulation shows that the linewidth and the turns of the coil influence the induced voltage greatly. The optimized electromagnetic vibration energy harvester can generate 0.7 μW of maximal output power with peak–peak voltage of 42.6 mV in an input vibration frequency of 94.5 Hz and input acceleration of 4.94 m/s2 (this vibration is a kind of low level ambient vibration). A prototype (not optimized) has been fabricated using MEMS micromachining technology. The testing results show that the prototype can generate induced voltage (peak–peak) of 18 mV and output power of 0.61 μW for 14.9 m/s2 external acceleration at its resonant frequency of 55 Hz (this vibration is not in a low ambient vibration level).

A micro electromagnetic generator for vibration energy harvesting

Vibration energy harvesting is receiving a considerable amount of interest as a means for powering wireless sensor nodes. This paper presents a small (component volume 0.1 cm3, practical volume 0.15 cm3) electromagnetic generator utilizing discrete components and optimized for a low ambient vibration level based upon real application data. The generator uses four magnets arranged on an etched cantilever with a wound coil located within the moving magnetic field. Magnet size and coil properties were optimized, with the final device producing 46 µW in a resistive load of 4 kΩ from just 0.59 m s−2 acceleration levels at its resonant frequency of 52 Hz. A voltage of 428 mVrms was obtained from the generator with a 2300 turn coil which has proved sufficient for subsequent rectification and voltage step-up circuitry. The generator delivers 30% of the power supplied from the environment to useful electrical power in the load. This generator compares very favourably with other demonstrated examples in the literature, both in terms of normalized power density and efficiency.