Vibration Output Research Articles

Vibrational coupling-based multilayer flexible triboelectric nanogenerator for wide-amplitude omnidirectional wave energy harvesting

Wave energy harvesters are viewed as potential foundations for self-powered wireless sensor devices. In this study, a multilayer flexible triboelectric nanogenerator (MFLU-TENG) is proposed and evaluated, which combines the stretching properties of springs and the deformation properties of flexible materials to enable wide-wavelength energy harvesting. It captures wave energy even at very low amplitudes, requiring a minimum wave amplitude of 5 cm for energy recovery. The study explores how geometric parameters of the MFLU-TENG affect vibration behavior and output performance. Optimal performance is achieved when varying the thickness of the PETG cushioning layer, resulting in a peak power density of up to 7.7 mW/m2. Three MFLU-TENGs connected in parallel successfully power 15 LEDs. And four parallel groups of MFLU-TENGs charged a 100µF capacitor to 5.3 V in 198 s and successfully powered the temperature and humidity sensor. And the MFLU-TENGs charge the 100uf capacitor to 4.0v and power the clock in 153 s. These findings underscore the MFLU-TENG’s potential as a cost-effective and efficient wave energy harvesting device, using renewable wave energy to power sensors or microelectronic devices in the Internet of Things.

Performing Magnetic Boundary Modulation to Broaden the Operational Wind Speed Range of a Piezoelectric Cantilever-Type Wind Energy Harvester

Small piezoelectric wind-induced vibration energy harvesting systems have been widely studied to provide long-term sustainable green energy for a large number of wireless sensor network nodes. Piezoelectric materials are commonly utilized as transducers because of their ability to produce high output power density and their simple structure, but they are prone to material fracture under large deformation conditions. This paper proposes a magnetic boundary modulated stepped beam wind energy harvesting system. On the one hand, the design incorporates a composite stepped beam with both high- and low-stiffness components, allowing for efficient vibration and electrical energy output at low wind speeds. On the other hand, a magnetic boundary constraint mechanism is constructed to prevent the piezoelectric sheet from breaking due to excessive deformation. Experiments have confirmed that the effective operational wind speed range of the harvester with magnetic boundary constraints is doubled compared to that of the harvester without magnetic boundary constraints. Furthermore, by adjusting the magnetic pole spacing of the boundary, the harvesting system can generate sufficiently high output power under high-wind-speed conditions without damaging the piezoelectric sheet.

Quality control on vibrator ground force in land vibroseis acquisition

Many quality control (QC) methods are used to monitor the output force from seismic vibrators. These QC tools usually provide the vibrator output force in three aspects — fundamental force, phase, and harmonic distortion — to measure the quality of the ground force compared with the predetermined sweep. As the vibrator works on challenging earth surfaces, such as unconsolidated ground surfaces, the peak harmonic distortion, a key vibrator QC parameter, always exceeds its QC threshold. This necessitates a vibrator reshoot and thereby a degradation of productivity. The purpose of this paper is to demonstrate that in unconsolidated ground surface areas a new setting of the harmonic cutoff frequency on a vibrator controller is recommended. This new setting reduces the unnecessary harmonics around 200 Hz so that the peak harmonic distortion is controlled in the required QC range. Therefore, unnecessary vibrator reshoots can be avoided, leading to improved productivity.

Chromaticity Recognition Technology of Colored Noise and Operational Modal Analysis

Operational Modal Analysis (OMA) refers to the modal analysis with only output vibration signals of a structure in its operating state. Classic OMA has developed multiple recognition methods in both the time and frequency domains, where when the random excitation is unknown, the excitation chromaticity is usually treated as white color, which can often cause errors and affect the accuracy of identifying frequencies or damping ratios. In this article, the chromaticity recognition function is defined and a method Chromaticity Recognition Technology (CRT) for identifying noise chromaticity based on system response is proposed. Then, a simulation example is presented. The noise chromaticity is identified for the response of the system under four types of colored noise excitation, and the results of the identification of operational mode parameters with and without CRT are compared. Furthermore, the sensitivity of traditional OMA to different colored noise has been investigated. An experiment with a cantilever under base excitation of pink noise has been undertaken and the results demonstrate the feasibility of the proposed CRT in this paper.

Rapid Estimation Model for Wake Disturbances in Offshore Floating Wind Turbines

The precise wake model is crucial for accurately estimating wind farm loads and power, playing a key role in wake control within wind farms. This study proposes a segmented dual-Gaussian wake model, which is built upon existing dual-Gaussian wake models but places greater emphasis on the influence of initial wake generation and evolution processes on the wind speed profile in the near-wake region. The enhanced model optimizes the wake speed profile in the near-wake region and improves the accuracy of wake diffusion throughout the entire flow field. Furthermore, the optimized dual-Gaussian wake model is utilized to estimate the power output and blade root vibration loads in offshore wind farms. Through comparative analysis of high-fidelity simulation results and actual measurement data, the accuracy of the optimized dual-Gaussian wake model is validated. This approach offers high computational efficiency and provides valuable insights for load fluctuations and power estimation, thereby advancing the development of wake control strategies rapidly.

Research on piezoelectric simulation characteristics based on ALN piezoelectric thin film structure

AlN piezoelectric thin films possess exceptional performance and find extensive applications in the fields of underwater acoustic communication and hydroacoustic sensing. To enhance the output voltage values of AlN piezoelectric thin films and optimize their structure, comprehensive simulations and analyses were carried out by using COMSOL on both circular and square film configurations. These investigations specifically focused on examining the impact of dimensional variations on resonance frequency and output voltage, as well as exploring the relationship between vibration frequency and output voltage. The findings revealed that by employing an appropriate cavity radius, increasing the thickness of the thin film can effectively enhance the output voltage. However, if the thickness surpasses 1.5 μm, the output voltage will gradually decline. Notably, the square film exhibited a significantly higher output voltage measurement of 2158 pm compared to the circular film.

Nonlinear vibration and amplitude ratio output performance of a resonant micro-gyroscope based on bifurcation detection

In this paper, we design a 3-degree-of-freedom (3-DOF) nonlinear resonant micro-gyroscope, which innovatively utilizes the bifurcation phenomenon of the nonlinear resonant beam as a detection method and uses the amplitude ratio before and after bifurcation as the sensitivity output of the system. The steady-state response of the driving equation is first solved by the complex exponential method. Coriolis force is amplified by the lever mechanism and transmitted to the axial direction of the resonant beam. The dimensions of the resonant beam are designed so that the frequency of Coriolis force is in a 2:1 relationship with the natural frequency of the resonant beam to enhance the parametric excitation effect. Subsequently, Hamilton principle and Galerkin method are used to derive and discretize the dynamical equations of the resonant beam containing axial force, respectively. The multi-scale method is used to perturbation analysis of discrete equations. Finally, the bifurcation characteristics and the amplitude-frequency response with different input angular velocities are studied. The results show that the comprehensive performance of the micro-gyroscope system using backward frequency sweep (BFS) is better than forward frequency sweep (FFS). Furthermore, by using the BFS, the relative sensitivity of the nonlinear resonant micro-gyroscope based on the amplitude ratio variation rises by about 168 times compared with that based on the frequency variation in the linear case. In addition, when considering the input angular velocity with the same magnitude but different directions, the bifurcation frequency of resonant beam is closely related to the direction of the input angular velocity, and the direction of the input angular velocity can be further identified by utilizing this phenomenon.

Dynamic response of Camellia oleifera fruit-branch based on mathematical model and high-speed photography

In order to study the motion law and shedding characteristics of fruits during the vibration harvesting process of Camellia oleifera fruit. The dynamic equation of fruit-branch picking was established, the vibration output solution and picking inertial force of Camellia oleifera fruit forced vibration were solved by mathematical methods, and the spectral curve between picking force and frequency when forced vibration of Camellia oleifera fruit was analysed by MATLAB. The three-dimensional model of fruit-branch was established, and the modal analysis and harmonious response analysis were carried out, and the optimal excitation frequency range was 4–8 Hz, and the optimal excitation load of fruit-branch was 50N. The self-made canopy camellia fruit picker was used to continuously vibrate the side branches of Camellia oleifera, and the high-speed camera was used to record the movement process of Camellia oleifera fruit at different vibration frequencies, and the results showed that the movement trajectory of Camellia oleifera fruit was complex and the result of a combination of multiple movements. With the increase of excitation frequency, the speed and acceleration of fruit and flower buds also increased, but the average shedding force of fruits and buds did not change much, and the average shedding force of flower buds was greater than that of fruits. The results of this experiment are basically consistent with the results of the simulation analysis. The results of this study can provide a theoretical basis for the design, selection and research and development of mechanical harvesting equipment.

Design and performance analysis of 3-D braided piezoelectric composite vibration energy harvester

In this article, an innovative three-dimensional (3-D) braided piezoelectric composite vibration energy harvester (BPCVEH) is designed. The geometry and representative volume unit (RVU) models of the 3-D braided piezoelectric composites (BPCs) are established based on the braided process. The effective elastic, piezoelectric, and dielectric constants of the 3-D BPCs are also predicted. The electro-mechanical coupling vibration equation of the 3-D BPCVEH under forced vibration is derived, and its output response and vibration mode are analyzed. The effects of environment frequency, load resistance, and external excitation acceleration on the voltage and power response of 3-D BPCVEH with different volume fractions are studied.

A real time digital vibration acceleration fiber sensing system based on a multi-carrier modulation/demodulation technique

A multi-longitudinal mode fiber laser sensor (MLMFLS) system based on digital modulation/demodulation technique for vibration acceleration detection is proposed. To the best of the authors’ knowledge, this is the first digital vibration acceleration demodulation system ever reported by a MLMFLS system. A few beat frequency signals (BFS) generated by the MLMFLS are used as signal carriers of applied vibration signals. Based on multi-channel digital down-conversion technique, the weak vibration signals modulated on the BFS are superposed by utilizing the digital universal software radio peripheral (USRP). The signal-to-noise ratio (SNR) of the output vibration signal is greatly enhanced. A spectral subtraction method is also utilized to improve the SNR of the demodulated vibration signal. The acceleration of the vibration signal is obtained after second order differential of the time domain vibration signal. By simply changing the position of window function of short-time Fourier transform, a real-time vibration frequency and acceleration sensing system is achieved. The measurement results demonstrated a minimum detectable acceleration of 0.03 g at vibration frequency of 1.0 Hz by the designed sensing system. It also has a simple structure, high signal-to-noise ratio and stability.

Design and experiment of a double-sided staggered conical teeth traveling wave ultrasonic motor

This paper proposed a double-sided staggered conical teeth traveling wave rotating ultrasonic motor based on in-plane bending mode, which reduces the difficulty of rotor preload application and improves the output characteristics of in-plane bending mode traveling wave rotating ultrasonic motor. The motor has four sets of drive teeth alternately distributed on both the inner and outer sides of the vibrator, with the drive teeth gap dedicated to accommodate the piezoelectric ceramic piece, and the staggered drive teeth on both sides of the vibrator are used to drive the rotor rotation. The motor operates in two in-plane third-order bending modes with the same frequency and orthogonal to each other, and is excited by four sets of piezoelectric ceramic disks spaced 90 degrees apart from the inner and outer sides. After the prototype was completed, its vibration characteristics and output performance were experimentally tested, and the actual effects of the three excitation schemes were compared. The experimental results show that the motor can provide a maximum output torque of 1.82 N·mm and a maximum no-load speed of 96.4 rpm when the excitation voltage is 300 V and the excitation frequency is 20.60 kHz.

A Hand-Held Device Presenting Haptic Directional Cues for the Visually Impaired.

Haptic information is essential in everyday activities, especially for visually impaired people in terms of real-world navigation. Since human haptic sensory processing is nonlinear, asymmetric vibrations have been widely studied to create a pulling sensation for the delivery of directional haptic cues. However, the design of an input control signal that generates asymmetric vibrations has not yet been parameterised. In particular, it is unclear how to quantify the asymmetry of the output vibrations to create a better pulling sensation. To better understand the design of an input control signal that generates haptic directional cues, we evaluated the effect of the pulling sensations corresponding to the three adjustable parameters (i.e., delay time, ramp-down step length, and cut-off voltage) in a commonly applied step-ramp input signal. The results of a displacement measurement and a psychophysical experiment demonstrate that when the quantified asymmetry ratio is in a range of 0.3430-0.3508 with an optimised cut-off voltage for our hand-held device, the haptic directional cues are better perceived by participants. Additionally, the results also showed a superior performance in haptic delivery by shear forces than normal forces.

A harmonic suppression method for low-frequency electromagnetic vibrators

Due to various nonlinear factors in an ordinary electromagnetic vibrator, the distortion of its output vibration waveform will always happen, especially at low frequencies (≤20 Hz), which blocks its application in a lot of area. To improve the acceleration waveform precision and reduce distortions at low frequencies, a waveform harmonic suppression method for low-frequency electromagnetic vibrators is proposed. After extracting the harmonic components in the output acceleration waveforms, a digital composite signal with harmonic compensation components is prospected according to the frequency response characteristic of the vibrator, and then sent back to drive the vibrator, which results in that the harmonic components in the formal waveform is suppressed. The proposed method was verified by simulations and experiments, and results show that the total harmonic distortions (THDs) of accelerations are reduced effectively at low frequencies, typically from 23% to less than 2% at the frequency as low as 0.1 Hz. The method is stable and robust because there is no real-time feedback loop in the system.

Feasibility study on a full‐scale wind turbine blade monitoring campaign: Comparing performance and robustness of features extracted from medium‐frequency active vibrations

AbstractThe present work investigates the performance of different features, extracted from vibration‐based data, for structural health monitoring of a 52‐meter wind turbine blade during fatigue testing. An active vibration monitoring system was used during the test campaign, providing periodic excitation of single frequencies in the medium‐frequency range, and using accelerometers to measure the vibration output on different parts of the blade. Based on previous work from the authors, data is available for the wind turbine blade in healthy state, with a manually induced damage, and with progressively increasing damage severity. Using the vibration data, different signal processing methods are used to extract damage‐sensitive features. Time series methods and time‐frequency domain methods are used to quantify the applied active vibration signal. Using outlier analysis, the health state of the blade is classified, and the classification accuracy through use of the different features is compared. Highest performance is generally obtained by auto‐regressive modeling of the vibration outputs, using the auto‐regressive parameters as features. Finally, suggestions for future improvements of the present method toward practical implementation are given.

Enhanced piezoelectric energy harvesting performance using trailing-edge flap

This paper proposes a novel piezoelectric energy harvester attached with a trailing-edge flap under various installation angles, for enhancing the aeroelastic vibration and improving the harvesting performance. The mathematical models of the fluid-structure-electric coupled fields are derived, the simulation models of the multi-physical coupled fields of the harvester system with various installation angle flaps are established, and the experimental prototypes of the harvester are fabricated. The influences of the flap installation angles on the flow field and output characteristics are investigated theoretically, numerically, and experimentally. The results demonstrate that the flap stiffness and damping coefficients exert less influence on vibration characteristics and harvesting performance. The flap at a certain installation angle alters the flow field, affects the flow pattern, restricts the vortex shedding, and offsets the aerodynamic force and moment. A decrease in the flap installation angles results in increasing the vibration response and output performance. The obtained numerical results are in good agreement with the experimental and theoretical values, which verifies the effectiveness of the simulation model. The maximum plunge amplitude is 0.029 m and the output voltage is 15.51 V at 17.74 m/s and an installation angle of 0o. The enhancement ratio of the output voltage at 0o is up to 148.6% over 45o, which achieves better harvesting performance. The designed harvester system powers indirectly the pedometer for 104 s at 13.58 m/s. This research offers an essential foundation for achieving better tradeoffs in energy harvesting and vibration suppressing by appropriately selecting the flap installation angle.

Relative importance and interactions of parameters of finite-element models of human middle ear.

In the last decades, finite-element models of the middle ear have been widely used to predict the middle-ear vibration outputs. Even with the simplest linear assumption for material properties of the structures in the middle ear, these models need tens of parameters. Due to the complexities of measurements of material properties of these structures, accurate estimations of the values of most of these parameters are not possible. In this study, we benefited from the stochastic finite-element model of the middle ear we had developed in the past, to perform global sensitivity analysis. For this aim, we implemented Sobol' sensitivity analysis which ranks the importance of all uncertain parameters and interactions among them at different frequencies. To decrease the computational costs, we found Sobol' indices from surrogate models that we created using stochastic finite-element results and the polynomial chaos expansion method. Based on the results, the Young's modulus and thickness of the tympanic membrane, Young's modulus and damping of the stapedial annular ligaments, and the Young's modulus of ossicles are among the parameters with the greatest impacts on vibrations of the umbo and stapes footplate. Furthermore, the most significant interactions happen between the Young's modulus and thickness of the tympanic membrane.

Vibration Triggered Leakage of Surface Charge on Epoxy Insulator Under DC Voltage

Surface charge accumulation is considered a critical threat to the safe operation of epoxy insulators installed in gas-insulated switchgear (GIS). This paper reports on the charge leakage phenomenon of the insulator with the occurrence of impact vibration under DC voltage. A full-sized disc insulator with a multi-arc surface profile was employed as the test sample. A vibration system was established to output vibration to the insulator in two Modes. In Mode I, the maximum acceleration was 338.9 m/s2 and the impact frequency was 1.1 Hz. In Mode II, the maximum acceleration decreased to 4.6 m/s2 but the impact frequency increased to 107.5 Hz. The charge densities on the insulator surface were measured before and after the vibrations. The results indicated that the vibration led to the obvious leakage of homo-charges during the DC stressing process, especially in the non-planar region. The leakage of homo-charges under positive stressing was more remarkable than that under negative stressing. The reduction of homo-charge quantity was more serious in Mode I than in Mode II. It is suggested that the vibration-triggered charge leakage is mainly due to charge de-trapping caused by micro-displacement of molecular chain occurring in the insulator with the vibration and subsequent charge release to the gas phase under the normal electric field, by which the surface charge accumulation quantity is remarkably reduced.

Enhanced high‐power performance of Fe‐doped PZMNZT piezoelectric ceramics

AbstractHigh‐power piezoelectric ceramics are typically driven to output vibration velocity (v0) under high AC electric fields. Herein, the Fe2O3 doped 0.125 Pb(Zn1/3Nb2/3) O3–0.075 Pb(Mn1/3Nb2/3)O3–0.8 Pb(Zr0.48Ti0.52)O3(PZMNZT–xFe; x = 0.05–0.35) piezoelectric ceramics were prepared to enhance v0, and the favorable comprehensive electrical properties, such as d33 = 315 pC/N, Qm = 1738, kp = 0.58, kt = 0.48, εr = 1156, tan δ = 0.4%, and Tc = 320°C, were achieved in the PZMNZT–0.15Fe ceramic. Most importantly, the PZMNZT–0.15Fe ceramic presented a reliable v0 of 0.90 m/s, which was 2.25 times of the commercial PZT4 ceramic (∼0.40 m/s). The excellent high‐power performance should be attributed to ordering functional elements such as crystal grains and ferroelectric domains. Overall, this work reveals that the PZMNZT–0.15Fe ceramic is competitive for high‐power applications.

A ring-type traveling wave linear ultrasonic motor based on in-plane third-order modal vibration

This paper proposes a new type of circular ring traveling wave linear ultrasonic motor with incomplete teeth. The motor’s movable slider is pressed against the end face of the tooth structure on the outer surface of the circular ring vibrator under a certain pre-pressure, four piezoelectric ceramic plates are evenly distributed at 90° intervals on the inner side of the circular structure, and four sets of driving teeth are arranged at 45° intervals from the position of the piezoelectric ceramic plates.When the motor is in operation, only one driving tooth works, and the life of the ultrasonic motor can be increased by rotating the different working teeth. The motor operates in two in-plane third-order bending modes that are orthogonal to each other at the same frequency. The dynamic design and simulation of the vibrator was carried out using ANSYS finite element software to analyze the effect of the structure on the mode. The principle prototype was fabricated, and the operating mode of the vibrator was measured using a laser Doppler vibrometer (LDV), and the vibration characteristics and output performance of the prototype were tested. Experimental results show that the motor runs smoothly at the excitation voltage of 240 V peak-to-peak, the excitation frequency of 30.459 kHz and the pre-pressure of 0.6 N, with the maximum output force of 90 mN and the motor no-load speed of 102 mm/s.

Enhanced airfoil-based flutter piezoelectric energy harvester via coupling magnetic force

This paper proposes a novel magnetic coupled airfoil-based flutter piezoelectric energy harvester, for decreasing the critical velocity, broadening the working bandwidth, and achieving more efficient harvesting performance at lower airflow velocity. The conceptual designing of the harvester system via coupling magnetic force is first conducted, the mathematical and simulation models of the fluid–structure-electric–magnetic coupled fields are then established, and the experimental prototypes are finally fabricated. The influences of the structural parameters of the harvester system on the vibration response and output performance are fully studied. The results show that the magnetic repulsion force decreases the equivalent stiffness of the harvester system and makes it easy to couple plunge-pitch motions. A decrease in the magnet spacing distances leads to decreasing the critical velocity and improving the output performance. Compared with the magnetic spacing distance of 25 mm, the critical velocity with the magnetic spacing distance of 17 mm decreases by 70%, and the enhancement ratio of output power increases by 50% at 13.8 m/s. The flow field demonstrates that the alternating pressure difference drives the harvester system to take place two DOF plunge-pitch motions. The experimental results are in good agreement with the theoretical values, which verified the established mathematical model. The designed magnetic coupled airfoil-based flutter harvester system achieves a larger vibration response and better harvesting performance at lower airflow velocity. This work provides essential foundations for achieving better harvesting performance via coupling magnetic force.