Input Vibration Research Articles

Perforated auxetic honeycomb booster with reentrant chirality: A new design for high-efficiency piezoelectric energy harvesting

The present study develops an auxetic meta-structure booster to advance piezoelectric energy harvesting (PEH). The model comprised a three-dimensional (3D) cantilever beam equipped with an auxetic substrate bonded to a piezoelectric (PZT) point defect using an epoxy layer. The substrate used in this proposed energy harvester possesses an auxetic region responsible for generating auxetic behavior and concentrating stress in the PZT layer. The auxetic model called auxetic structure (AS)-II is inspired by ancient motifs and is designed based on the combination of several promising mechanisms, including reentrant, chiral, perforation, and honeycomb supercell. The finite element method is employed to create numerical models whose accuracy is confirmed by mesh convergence and available experimental data. A parametric study is conducted on the AS-II harvester to examine the influence of geometry and PZT material type on the harvested electrical power. Our research efforts stem from both mechanical and electrical circuit fields to fulfill the broadband design target within the desired ultra-low-frequency range of regardless of the resonance condition. As a result, the impact of other factors, such as load resistance, frequency, load amplitude, and bonding stiffness, on the PEH performance is further investigated. The reason behind such outstanding performance of AS-II is explained in terms of geometrical physics and stress distribution. The effect of geometrical dimensions on the auxetic behavior is also analyzed using Poisson’s ratio (PR) study. Subsequently, we demonstrate that this innovative adapter can advance the system’s performance in terms of harvested power and lightweight by a magnification factor of and times that of a plain substrate and and 3.16 times that of a conventional auxetic harvester, respectively. The present harvester is strain controllable, where it can set PR between and resulting in robust PEH even if switching input vibration from high to low levels. This new idea enables us to serve cantilever-type resonators at frequencies far lower than their resonant frequencies with small portions of incident excitement.

A novel vision transformer network for rolling bearing remaining useful life prediction

The accurate predictions of remaining useful life (RUL) have become a key and extremely challenging problem. Due to the limitations of the classical convolutional neural network and recurrent neural network structure, the attention mechanism has been introduced to improve feature representation of the long-term bearing degradation data. Transformer network based on attention mechanism is successfully applied in many fields and recognized as an excellent creation for deep learning models. In this paper, a novel lightweight mobile vision transformer (MobileViT) architecture based on deep networks is proposed for the RUL predictions. This new network is named prognostics separable vision Transformer (ProgSViT), which combines the separable convolution and MobileViT. In ProgSViT network, the separable convolutions are first constructed for extracting local feature from the input vibration signal, and the new vision transformer architecture is proposed to learn the global feature representations. In improved MobileViT model, the loss function is optimized, and a new training strategy is provided. Finally, the obtained features are input to the global average pool layers and the full connection layers to perform RUL estimation. Experiment results present the proposed ProgSViT network surpasses the other models in RUL predicting, which possesses higher precision and computational efficiency.

Unleashing multi-scale mechanical enhancement in NiTi shape memory alloy via annular intra-laser deposition with homogenized Ti2Ni nanoprecipitates

Additive manufacturing (AM) of composition-sensitive NiTi shape memory alloys (SMAs) is hindered by uncontrollable non-equilibrium microstructures, leading to functional performance degradation and limitations in high-throughput net-shaping applications. To address these challenges, we propose a novel approach combining annular intra-laser directed energy deposition (AIL-DED) with a tailored gradient post-treatment process. This enables the fabrication of nanocomposite microstructures in NiTi SMAs with precise control over the homogenization of Ti2Ni nanoprecipitates. In-situ monitoring and characterization of thermal history, microstrain, and constitutional phases, were utilized to uncover the relationship between multi-scale structural features and mechanical responses. The interplay between laser reflectivity, energy input, and lattice thermal vibrations affects forming quality in AIL-DED. Dynamic temperature variations were studied before reaching thermal equilibrium, revealing insights into thermal and mechanical interactions during the process. These findings contribute to understanding challenges in fabricating high-quality NiTi SMAs. Examining phase transformation behavior and its correlation with processing parameters deepens understanding of microstructural evolution and provides insights for tailoring material properties. The stress relaxation and dislocation evacuation at elevated temperatures caused the expansion of lattice and interplanar spacing in the age-treated SMA's B2 matrix phase, exhibiting a stable two-step phase transformation behavior (B19′↔R↔B2). AIL-DED combined with two-stage heat treatment strategy demonstrated enhanced homogeneity of non-equilibrium microstructures, resulting in the formation of high-density, well-dispersed Ti2Ni nanoprecipitates, with a semi-coherent interface to B2 matrix. The combination of load-bearing strengthening through well-dispersed Ti2Ni nanoprecipitates and Orowan strengthening at the semi-coherent interface yielded simultaneous enhancements in nanohardness, ultimate compressive strength, compressive fracture strain, and deformation recovery, following the AIL-DED combined with two-stage heat treatment process. The fracture mechanism transitioned from a mixture of brittle-ductile behavior to predominantly ductile characteristics. This study provides valuable insights that advance additive manufacturing and enhance the functional performance of SMAs in critical applications.

Quantification of damage expansion influence on frequency response function of plate for structural health monitoring with integral differential method

This paper presents a feasibility study on damage size quantification throughout the damage expansion procedure using the integral differential method based on the developed frequency response function (FRF) programme. A designed pattern of piezoelectric Micro Fibre Composite (MFC) transducers was integrated with three composite panels for a real time monitoring testing by swept sine vibration input signals under three varied frequency bandwidths ranged from 10 to 1 kHz, 1k-3 kHz and 3k-5 kHz, respectively. The composite panels under pristine stage without any impact damages were tested and documented as a cross-reference for subsequent quantification estimation. The damages were introduced around transducers array, and its expansion process is equivalently simulated by a repetitive impact test procedure. A modified damage index, difference of response (DoR), was derived through integral differential method to assess the FRF outcome change of damaged composite plate relative to the pristine state. Combined with damage geometrical dimensions measured by thermography imaging technology, a quantification formula is derived reversely through numerical analysis, which showed a segmentation linear relation between the DoR and damage size governed by the power and logarithmic functions. The damages under different severity subjected to an additional composite plate were successfully quantified by the segmentation formula, which validate the feasibility of quantification with DoR.

Effect of pulse on fragility curves of buckling-restrained braced frames

To investigate the effect of presence of the pulse in earthquake motions on the vulnerability of buckling-restrained braced frames (BRBFs), this technical note uses pulse-like ground motions (original records) and their residual parts obtained by extracting the pulse via wavelet analysis, as input vibrations. Conducting the numerical simulation of 4, 8, 12, and 15-storey BRBFs, their responses to the scaled original and residual motions are recorded using incremental dynamic analysis (IDA). Accordingly, the seismic performance of BRBFs is generally evaluated, and fragility curves are developed at collapse prevention (CP), life safety (LS), and immediate occupancy (IO) performance levels. The results indicate that a maximum difference of about 25%–30% may occur between the fragility curves due to the original and residual parts of ground motions at the maximum considered earthquake (MCE) intensity level for 8, 12, and 15-storey BRBFs, so that the original records lead to a severe damage in comparison with the residual ones. Also, the original records increase the probability by 20% on average compared to the residual records at the LS level for the considered BRBFs.

An Improved DC-DC Boost Converter for Energy Harvesting

A novel dual-input DC-DC boost converter that can perform the integration of harvested energy from solar and vibrational input energy sources is proposed. Firstly, the background of a hybrid energy system that relates to multi-input DC-DC converters is discussed, and the limitations of the current designs of power converter ICs are highlighted. A detailed design analysis of the proposed converter was done to justify its performance. A current and voltage stress analysis has been performed to ensure suitable switching devices are selected for the converter. Two different power control strategies are proposed for the DIDCB converter to manage output voltage during source and load-side disturbances. Performance analysis of the circuit is carried out using MATLAB Simulink software. Different duty ratios for power switches in the converter were tested to determine the maximum boost ratio and the highest efficiency that can be achieved by the converter. To demonstrate the feasibility of the proposed converter, the performance of the converter is compared with existing converter topologies. The proposed converter achieved a high efficiency of 99.4%, had less fluctuation in the output voltage, and had reduced overshoot. In addition, the proposed converter demonstrated a simpler configuration and required fewer component counts, which helped reduce the cost and size of the system.

Driveline System Effects on Powertrain Mounting Optimization for Vibration Isolation under Actual Vehicle Conditions

<div>Vehicle vibration is the key consideration in the early stage of vehicle development. The most dynamic system in a vehicle is the powertrain system, which is a source of various frequency vibration inputs to the vehicle. Mostly for powertrain mounting system design, only the uncoupled powertrain system is considered. However, in real situations, other subsystems are also attached to the powertrain unit. Thereby, assuming only the powertrain unit ignores the dynamic interactions among the powertrain and other systems. To address this shortcoming, a coupled powertrain and driveline mounting system problem is formulated and examined. This 16 DOF problem is constructed around a case of a front engine-based powertrain unit attached to the driveline system, which as an assembly resting on other systems such as chassis, suspensions, axles, and tires. First, the effect of a driveline on torque roll axis and other rigid body modes decoupling is examined analytically in terms of eigensolutions and frequency responses. It is observed from the analysis that when the optimized uncoupled powertrain system is introduced in real vehicle conditions, the vibration isolation level of the powertrain mountings gets degraded. Then, a new improved approach of considering coupled powertrain and driveline systems in the initial design phase itself is proposed. The mounting system parameters such as mount location, mount orientation angle, and stiffness rate are optimized and redesigned for the proposed system. The results of the redesigned system show that the decoupling of the rigid body mode parameters is improved and consequently powertrain vibration performance is also improved in static and dynamic conditions of the vehicle. Overall, the findings of this study suggest that considering the driveline along with the powertrain as a coupled system at the early phase of the mounting system design itself improves the vibration performance of the vehicle during real-life situations.</div>

Kernel Regression Residual Decomposition-Based Polynomial Frequency Modulation Integral Algorithm to Identify Physical Parameters of Time-Varying Systems under Random Excitation

The physical parameters (stiffness, damping) of time-varying (TV) systems under random excitation provide valuable information for their working condition but they are often overwhelmed by noise interference. To overcome this problem, this paper presents a novel multi-level kernel regression residual decomposition method, which can not only effectively separate each modal component from the raw vibration acceleration signal, but also eliminate noise interference. Additionally, the multiple degree-of-freedom (DOF) parameter identification problem is transformed into a single DOF parameter identification problem. Combined with the derived polynomial frequency modulation integral algorithm and the cross-correlation theory based on the fractional Fourier ambiguity function, a physical parameter identification method is proposed. The method provides a new idea in modeling TV systems and identifying physical parameters under random excitation. To demonstrate the effectiveness of the proposed method, numerical simulations are conducted with three different cases of variation (variation, quadratic variation, and periodic variation) in time. Moreover, its robustness is evaluated by adding different signal-to-noise ratio levels of noise (20 dB, 50 dB, 100 dB) to the input vibration acceleration signal. The analysis results confirm the performance of the proposed method for the parameter identification of TV systems under random excitation.

Method and Experimental Study of Oscillator Frequency Optimization of Distributed Tuned Mass Dampers for Broadband Multimodal Vibration Mitigation of Reinforced Concrete Wall

Distributed tuned mass dampers (dTMD) can effectively mitigate the broadband vibration of a structure. However, when the vibration frequency in question reaches several hundred hertz, traditional optimization methods represented by fixed point theory are difficult to apply due to dense modal density, complex boundary conditions, and vibration inputs. This paper proposes the minimax method based on modal damping to optimize the oscillator’s frequency. Two typical wall panel specimens are tested to evaluate the proposed method. The mode shape of the uncontrolled wall and the vibration mitigation effect of the stacked sandwich-damped TMD under single-point bidirectional excitation is tested. The correlation between the modal damping and the vibration mitigation effect is evaluated. The results show that the RC wall panel has a dense mode when the frequency of interest reaches 300 Hz and above; the distributed stacked sandwich-damped TMDs can effectively mitigate the vibration of the RC wall panel in the frequency range of 200~450 Hz; and that the idea of optimizing the frequency of dTMD based on modal damping is feasible.

High-efficiency regenerative shock absorbers considering twin ball screws transmission for increasing the vehicles’ driving range using a hybrid approach

This article proposes a hybrid system for increasing the electric vehicles’ (EVs) driving range considering regenerative shock absorbers. The proposed hybrid approach is a combination of atomic orbital search (AOS) and wild horse optimizer (WHO); later, it was called AOSWHO method. The major objectives of the proposed work are to extend vehicle range, reduce the charging time of the vehicle, reduce the battery size, and increase the efficiency of vehicle. In this proposed work, linear Permanent magnet (PM) generators are used as the sole instrument and on-board source is utilized to absorb vibration energy of the moving vehicle. Here, the proposed method has four key modules: (a) suspension vibration input, (b) transmission mechanism, (c) generator module, and (d) power storage. A suspension vibration is mostly pretentious by road roughness and speed vibration, which is optimally handled by the proposed hybrid technique. The conversion of the alternating linear vibration into unidirectional rotation of generator shaft is processed by proposed hybrid technique. Based on the volume and efficiency of the dampers, a small volume, brushless DC motor with low rotor inertia is selected to produce electricity. By then, the proposed AOSWHO run on MATLAB site and its performance is related to several existing systems. From the simulation result, it is concluded that proposed system delivers an State of Charge (SOC) of 40.33, which is high compared to existing approaches.

Broadband Vibration-Based Energy Harvesting for Wireless Sensor Applications Using Frequency Upconversion.

Silicon-based kinetic energy converters employing variable capacitors, also known as electrostatic vibration energy harvesters, hold promise as power sources for Internet of Things devices. However, for most wireless applications, such as wearable technology or environmental and structural monitoring, the ambient vibration is often at relatively low frequencies (1-100 Hz). Since the power output of electrostatic harvesters is positively correlated to the frequency of capacitance oscillation, typical electrostatic energy harvesters, designed to match the natural frequency of ambient vibrations, do not produce sufficient power output. Moreover, energy conversion is limited to a narrow range of input frequencies. To address these shortcomings, an impacted-based electrostatic energy harvester is explored experimentally. The impact refers to electrode collision and it triggers frequency upconversion, namely a secondary high-frequency free oscillation of the electrodes overlapping with primary device oscillation tuned to input vibration frequency. The main purpose of high-frequency oscillation is to enable additional energy conversion cycles since this will increase the energy output. The devices investigated were fabricated using a commercial microfabrication foundry process and were experimentally studied. These devices exhibit non-uniform cross-section electrodes and a springless mass. The non-uniform width electrodes were used to prevent pull-in following electrode collision. Springless masses from different materials and sizes, such as 0.5 mm diameter Tungsten carbide, 0.8 mm diameter Tungsten carbide, zirconium dioxide, and silicon nitride, were added in an attempt to force collisions over a range of applied frequencies that would not otherwise result in collisions. The results show that the system operates over a relatively wide frequency range (up to 700 Hz frequency range), with the lower limit far below the natural frequency of the device. The addition of the springless mass successfully increased the device bandwidth. For example, at a low peak-to-peak vibration acceleration of 0.5 g (peak-to-peak), the addition of a zirconium dioxide ball doubled the device's bandwidth. Testing with different balls indicates that the different sizes and material properties have different effects on the device's performance, altering its mechanical and electrical damping.

Study on heterogeneous gas-solid structure and interparticle collision behavior in a vibrated fluidized bed of Geldart D particles using CFD-DEM simulations

The spatiotemporal characteristics of the heterogeneous gas-solid structure and interparticle collisions in fluidized beds of Geldart D particles with and without vibration were comparatively studied by the coupled CFD-DEM simulations. The effects of vibration on the spatiotemporal distributions of particle configuration and particle dynamics were revealed utilizing data visualization and frequency domain analysis. The results show that the input vibration facilitates the formation of square-nosed slugs and improves the uniformity of gas-solid contacts. Moreover, vibration causes fluctuations in static air pressure on the entire bed simultaneously. It is revealed that the introduction of vibration can significantly increase the intensity and uniformity of interparticle collisions, the number of particles involved in collisions, and the total kinetic energy of the bed. The results also show that there exists a positive correlation between average collision number and solid volume fraction while an inverse correlation between granular temperature and solid volume fraction.

Primary microvibration standards down to 10−3 m s−2 at low frequency

The reliability of microvibration measurements is important in some applications, such as infrastructure health monitoring. Thus, it is necessary to develop a vibration standard based on ISO16063-11 for microvibrations. In this study, the low-frequency standard vibration calibration system in the National Metrology Institute of Japan was upgraded to be compatible with small input vibrations down to an amplitude of 10−3 m s−2. A low-noise reference vibration measurement system and a precise signal processing method were integrated to reduce the background noise contribution, which is a dominant uncertainty source in the field of microvibration calibration. The developed system could calibrate the sensitivity of a low-noise accelerometer down to 10−3 m s−2, between 0.1 Hz and 100 Hz. This paper reports the calibration demonstration using a servo accelerometer and the evaluated uncertainty budget. The estimated calibration uncertainty was 0.1% for a normal calibration process with an excitation of 10 m s−2, and it was 2.1% for a microvibration calibration process with an excitation of 10−3 m s−2.

An H-shaped coupler energy harvester for application in heavy railways

The lack of onboard power supply for the sensors used for freight trailer safety monitoring. This paper proposes an H-shaped coupler energy harvester (HC-EH) for applications in heavy railways. The HC-EH is mainly divided into three modules: vibration input, motion conversion and energy conversion. When the train is in normal form, the adjacent couplers have relative motion used to excite the HC-EH through the vibration input module. Then the bidirectional reciprocations are converted into unidirectional rotations by the motion conversion module. The damage to the mechanical structure caused by the huge impact force between the couplings on the heavy railway is solved by the H-type structure with a parallel distribution of input and transmission utilized by the HC-EH. A generator converts kinetic energy into electricity stored in supercapacitors in the energy conversion module and provides power for the railway onboard monitoring sensor network. The system dynamics, performance and mechanical properties of full-scale prototypes were studied using mechanical testing and sensing fixtures. In the bench test, the peak and average output power were 9.67 W, and 5.14 W, respectively, and the peak efficiency was 56.49%. Finally, the practical applications of the proposed HC-EH in Datong-Qinhuangdao Railway are studied.

Tunable Dynamic Walking via Soft Twisted Beam Vibration

We propose a novel mechanism that propagates vibration through soft twisted beams, taking advantage of dynamically-coupled anisotropic stiffness to simplify the actuation of walking robots. Using dynamic simulation and experimental approaches, we show that the coupled stiffness of twisted beams with terrain contact can be controlled to generate a variety of complex trajectories by changing the frequency of the input signal. This work reveals how ground contact influences the system's dynamic behavior, supporting the design of walking robots inspired by this phenomenon. We also show that the proposed twisted beam produces a tunable walking gait from a single vibrational input.

Using Stapes Velocity to Estimate the Efficacy of Mechanical Stimulation of the Round Window With an Active Middle Ear Implant.

To test a method to measure the efficacy of active middle ear implants when coupled to the round window. Data previously published in Koka et al. ( Hear Res 2010;263:128-137) were used in this study. Simultaneous measurements of cochlear microphonics (CM) and stapes velocity in response to both acoustic stimulation (forward direction) and round window (RW) stimulation (reverse direction) with an active middle ear implant (AMEI) were made in seven ears in five chinchillas. For each stimulus frequency, the amplitude of the CM was measured separately as a function of intensity (dB SPL or dB mV). Equivalent vibrational input to the cochlea was determined by equating the acoustic and AMEI-generated CM amplitudes for a given intensity. In the condition of equivalent CM amplitude between acoustic and RW stimulation-generated output, we assume that the same vibrational input to the cochlea was present regardless of the route of stimulation. The measured stapes velocities for equivalent CM output from the two types of input were not significantly different for low and medium frequencies (0.25-4 kHz); however, the velocities for AMEI-RW drive were significantly lower for higher frequencies (4-14 kHz). Thus, for RM stimulation with an AMEI, stapes velocities can underestimate the mechanical input to the cochlea by ~20 dB for frequencies greater than ~4 kHz. This study confirms that stapes velocity (with the assumption of equivalent stapes velocity for forward and reverse stimulation) cannot be used as a proxy for effective input to the cochlea when it is stimulated in the reverse direction. Future research on application of intraoperative electrophysiological measurements during surgery (CM, compound action potential, or auditory brainstem response) for estimating efficacy and optimizing device coupling and performance is warranted.

NUMERICAL ANALYSES ON THE RESPONSES OF UNIMORPH AND BIMORPH PIEZOELECTRIC HARVESTERS IN TIME DOMAIN

The paper presents the assessment of the electric output rendered by a unimorph and a bimorph piezoelectric harvester, with one and two active piezoceramic wafers, using numerical simulations. Expected sinusoidal voltages were obtained in a time-dependent study, with a time step corresponding to the eigenfrequency found after conducting an Eigenfrequency study. The terminal voltages obtained agree with the Euler-Bernoulli beam theory and with the distance of the piezoelectric layers from the neutral fiber. By adding an electric circuit node to the electric field problem to form a closed internal circuit, a single unified sinusoidal voltage response should be obtained, coinciding with the input vibration signal. The independent voltages of the layers of a piezoelectric structure with more than one layer (usually two or four) cannot be observed experimentally, as a harvester has only two terminals that pick the overall electric response from all the layers, giving a single alternating voltage output.

Vibration Response of Walnuts under Vibration Harvesting

Vibration harvesting is a promising method for walnut production owing to its low cost and high efficiency. However, current research focuses on simulation analysis and lacks a theoretical model explaining the walnuts’ specific vibration response. This affects the design of the input vibration parameters during harvesting and thus reduces the harvesting efficiency. In this paper, a novel theoretical model of walnuts during vibration harvesting was established to analyze the vibration response, including the motion morphology (motion trajectory and dropping position) and detachment force. A field test was then carried out to verify the theoretical model. The theoretical and experimental results showed that the motion trajectory of the walnuts during vibration harvesting is similar to an ellipse, and the dropping position is at either of the two end points of the trajectory. The detachment force was found to be proportional to the vibration amplitude and the square of the vibration frequency theoretically. This paper provides a theoretical reference for designing the optimal input vibration parameters of a harvesting device to improve the harvesting rate of walnuts.

Defining a vibration test profile for assessing the durability of electric motorcycle battery assemblies

There has been little published research critically examining the vibration loading that battery assemblies within large sized electric two wheelers (ETWs) experience during their lifetime. Much of the existing research has been focused on assessing the battery packs of electric passenger vehicles, which have a different dynamic response to their two wheeled counterparts. Existing automotive procedures, therefore, cannot be applied to these modes of transport. It is important therefore that the magnitude and frequency of the vibration inputs that the ETW battery will be exposed to during the vehicle's life is understood.For the first time, this study describes a methodology to derive random power spectral density (PSD) profiles that are representative of 60,000 miles of UK customer electric motorcycle (EM) usage for a vehicle operating in the large traditional motorcycle class. The derived PSDs are suitable for testing frame mounted batteries for mechanical durability using modern shaker table facilities and are derived utilising vibration measurements from a contemporary EM (Harley Davidson Livewire). In addition, it compares the measurements from a current production EM to that of profiles derived from passenger electric vehicles (EVs) published within existing studies to highlight the key differences between vibration environments experienced by batteries within passenger EVs and EMs.

Optimal control of structural vibration using LQG algorithm

This paper proposes a Linear Quadratic Guassian Design (LQG) with based semi-active control algorithm for vibration reduction of building structures. The controlled damper force required by the structure has been calculated from an MR damper of load capacity 100N. A building frame has been selected to illustrate the performance of the proposed algorithm. Four different earthquake acceleration data has been used as input vibration data to the numerical frame. The proposed method of damping on the frame has been found to be more effective to reduce the structural response significantly in comparison with the conventional tuned liquid column damper. The developed method is efficient in providing the optimum control force required to the frame. Therefore, it minimizes the need of high damping capacity and the number of dampers. As a result, it reduces the cost of maintenance and structural control during earthquakes.