Vibration Environment Research Articles

Study of the Extremely Low-Frequency Noise Characteristics of a Micro-Thrust Measurement Platform.

The critical structural parameters are optimized and studied using the numerical simulation method to improve the resolution and stability of the Micro-Thrust Measurement Platform (MTMP). Under two different ground random vibration environments, the parameters, such as pivot thickness, pendulum rod length, and pivot structure, are focused on analyzing the influence of the system's resolution and stability. The results show that when the thickness of the pivot is 0.04 mm or 0.2 mm, and the pendulum rod length is 2 m, the effect of ground random vibration on the MTMP is minimized. At 0.1 mHz, it can reach 0.0057 μN/Hz. In the series double-pivot structure, an appropriate increase in the distance between the sheets can further optimize the above conclusions. The results and analysis within this study can provide support for the engineering design of the MTMP.

A piezoelectric energy harvester with parallel connection using beams of different lengths to improve output performance

The purpose of this paper is to design an energy harvester to improve output performance. The theoretical analysis of the piezoelectric energy harvester has been performed. Reducing the length of one cantilever beam, thereby changing the relative impact position, causing the amplitude of the two cantilever beams to be different, and making the waveform of two beams different. Some experiments have been tested to verify the feasibility of the device and compare the differences with Plan A. Based on the experiment, it can be concluded that the output voltage is higher at both high and low speeds. When the rotation speed is 255 r min−1, Plan B arrives at the optimum speed, and the maximum output voltage is 166.2 V, which significantly increases from 97.2 V of Plan A. The maximum output power is 0.966 W under the load resistance of 10 kΩ. The maximum voltage is 157.7 V under the load resistance of 120 kΩ. Nevertheless, the maximum voltage and maximum power of Plan A are 92.62 V and 0.52 W. Besides, the prototype has fewer materials and nearly 1.5 times the energy conversion rate compares to Plan A. It can light up 42 LEDs easily and can adapt to environmental vibration frequency changes, so it has an intensely adaptable and outstanding performance in practical applications.

Method of determination of integral and differential nonlinearities of ADC by three histograms during tests of diagnostic channels in complex magnetotherapy

One of the most important components of modern electronic systems in the fields of medical technology, automotive, 5G communications, etc. are microchips containing analog-to-digital converters (ADCs) on a single chip. Aging effects, environment and mechanical vibrations have a significant impact on the operation of electronic systems, so microcircuits need to be periodically verified, calibrated and even replaced. For this reason, in order to control metrological and technical characteristics of hardware and software of the "Multimag-M" complex, which contains diagnostic channels for measuring pulse wave, respiration process, blood pressure and blood oxygen saturation (saturation), it was proposed to introduce an automated block of control, testing and self-calibration into the structure of the chronomagnetotherapy complex [1]. Application of BIST (Build-in Self Test) - built-in means of self-testing is a promising approach to solving problems of reliability improvement of modern microcircuits [2]. Most of the known BIST methods of ADCs require on-chip highly linear test signal generator (TS) [3-4], which is the most complex block. The ability to test ADCs with a large number of digits is limited by the linearity of the TS generator and as the resolution of ADCs increases, it becomes a difficult task to provide linear TS generation on-chip. The aim of the work is to develop a method for determining the integral and differential nonlinearities of ADC independent of the linearity of the test signal. A method for determining the integral and differential nonlinearities of the ADC, taking into account the nonlinear component of the TS, is proposed. This is achieved by sequentially feeding to the input of the tested ADC a periodic TS of triangular shape, a level-shifted down TS and a level-shifted up TS. The first histogram of ADC codes distribution at absence of TS offset, and also the second and the third histograms at TS downward and upward shifting. Using the three linked histograms, the contribution of the nonlinear component of the TS to the integral nonlinearity for each ADC code is determined. Given the nonlinear component of the TS, the integral nonlinearity for each ADC code is further determined, and then the differential nonlinearity of the ADC is determined from the integral nonlinearity. In addition, the method determines the displacement voltages of the TS, which reduces the requirements for the accuracy of the displacement signal reference. The practical value of the research result lies in the application of the method reducing requirements to TS linearity at self-diagnostics and self-calibration of microcircuits containing ADCs will allow to reduce the complexity of crystal design.

Investigation of Metro Train-Induced Environmental Vibration Using a Coupled Sliced Finite Element-Infinite Element Model

Investigation of Metro Train-Induced Environmental Vibration Using a Coupled Sliced Finite Element-Infinite Element Model

Innovations in Thermoelectric Technology: From Materials to Applications

Over the past two decades, significant advances have been made in the field of energy harvesting, which involves the collection of energy from various environmental sources, including light, thermal gradients, electromagnetic radiation, and mechanical vibrations [...]

Research of the readout electronics for X-ray beam-position feedback system of SAPS

For 4th generation synchrotron radiation (SR) light sources, the X-ray beam-position stability is one of the crucial factors in cutting-edge experiments. Instead of traditional passive vibration isolation techniques, active vibration isolation measures based on feedback control technology have begun to play an important role for stabilizing the beam-position. The readout electronics of the feedback control system is presented in the paper. The proposed design is based on the integration of proportion integral differential (PID) controller and system on chip (SoC) module. By using the ARM for analyzing the convergence speed of PID controller with different parameters and configuring it, the readout electronics flexibly adapts to different vibration environments. The readout circuits based on this method is implemented for southern advanced photon source, and tests are carried out in the laboratory to evaluate the readout electronics. The results show that it can weaken the influence of vibration sources below 5Hz on the beam-position.

Exploiting multi-stiffness combination inspired absorbers for simultaneous energy harvesting and vibration mitigation

In scenarios where wide-amplitude shock excitation is encountered, a routine bistable configuration struggles to achieve satisfactory energy transfer, and a sensible combination of multiple nonlinear oscillators with different stiffness mechanisms can be exploited to achieve optimal vibration mitigation performance. In this paper, a nonlinear energy conversion and multi-stiffness combination inspired dynamic vibration absorber (NECMC-DVA) is proposed with a magnetic-spring tunable nonlinear stiffness element as the substructure. Parametric studies are performed for different modes of magnet-spring tunable nonlinear stiffness unit arrays considering transient impulses and harmonic excitation. The NECMC-DVA device, which comprises bistable oscillators, cubic stiffness oscillators, and hybrid stiffness oscillators, is also experimentally demonstrated for its synergistic performance in vibration mitigation and energy harvesting. The performance of the NECMC-DVA is measured under transient impulses and harmonic excitations. It has been found that the NECMC-DVA, which consists of a bistable oscillator, a cubic stiffness oscillator, a hybrid stiffness oscillator, energy-capture elements, and motor sequences, achieves high-efficiency nonlinear energy transfer and significant shock robustness in wide-amplitude impulsive scenarios. The NECMC-DVA with hybrid energy sinks demonstrates more remarkable targeted energy transfer and energy conversion performance than its pure bistable oscillator counterpart. Furthermore, the NECMC-DVA prototype can achieve adaptive vibration control modulation and energy conversion management through motion control boards by monitoring ambient excitation signals. Therefore, the NECMC-DVA enables integrated active and passive mitigation and energy harvesting to simultaneously accommodate multi-source indeterminate vibration and shock environments.

FE Model Updating of Continuous Beam Bridge Based on Response Surface Method

In this paper, A high-order response surface method is proposed for finite element model updating of continuous beam bridges. Firstly, based on visual inspection and environmental vibration testing, the peak picking (PP) method and random subspace identification (SSI) method are used to identify the dynamic characteristic parameters of the structure. Then, the finite element model of the continuous beam bridge is updated based on the third-order response surface method. It can be concluded that the results of the updated finite element model are in good agreement with the test results, and the maximum error between the calculated and measured frequency is less than 3%, with MAC values greater than 85%. Moreover, the updated finite element model can reflect the current situation of real bridges and serve as the basis for bridge health monitoring, damage detection, and safety assessment.

Stress isolations for resonant pressure micro sensors

This paper presents stress isolations for resonant pressure micro sensors that are supported by fixed isolation layers during assembly. While the resonant frequencies of the two resonators experience shifts due to measured pressures, they are susceptible to environmental perturbations. The proposed stress-isolated assembly in this study effectively mitigates the adverse effects of environmental noise and stabilizes the intrinsic frequencies of the resonators. Specifically, when subjected to temperature variations within the range of -55∼85 °C, the accuracy of the stress-isolated resonant pressure microsensor was determined to be ±0.01% FS. Similarly, during 3-axis random vibration tests, the accuracy of these stress-isolated resonant pressure microsensors was quantified as ±0.01% FS in response to environmental vibrations.

Effect of lead-free solder thermal interface material thickness on the reliability of electronic components in a random vibration environment

The reliability of electronic components has persistently posed challenges for engineers. This study addresses the critical need of understanding the impact of random vibration on the reliability of lead-free solder as thermal interface materials (TIM) within electronic components. ANSYS software was deployed to design, develop, and simulate the electronic model, with a focus on the TIM. SAC405 lead-free solder served as the TIM, its thickness was varied between 0.01 to 0.06 mm (at 0.01 mm intervals). The results from this investigation reveal relevant correlations. As the TIM thickness increases, there's a noticeable reduction in stress and strain while the deformation increases. Remarkably, a direct relationship emerges between TIM thickness and fatigue life; thicker TIM correlates with increased fatigue life. In addition, at a TIM thickness of 0.01 mm, the fatigue life measurements were 2.76 x 104, 1.63 x 104, and 0.792 x 104 for Equations 1, 2, and 3, respectively. These findings carry profound implications for engineers, serving as a guiding framework to aid in the selection of optimal TIM thickness for electronic components if lead-free solders are used as TIM. Understanding these trade-offs between stress, strain, deformation, and fatigue life is pivotal, empowering engineers to make informed decisions during electronic system design and development, ultimately enhancing overall reliability. Using lead-free solders as TIM in electronic applications is proposed by this study due to the thermal and reliability benefits presented.

Numerical Simulation and Influence of Non-Gaussian Vibrations on Flexible Robotic Systems

Random vibration excitation is a standard method for obtaining the dynamic properties of aerospace structures and simulating loading conditions. Shaker-based random excitation and traditional finite element analysis techniques use random vibrations, assuming a Gaussian distribution of excitation impulse magnitudes. While Gaussian signals may sufficiently describe some vibrational environments, many real-world excitations have non-Gaussian distributions. These signals may contain vibrational impulses larger than those observed in a Gaussian signal and could cause damage if not considered. This paper examines the influence of non-Gaussian signals on flexible vs. rigid robotic architectures using NASA JPL’s Pop-Up Flat Folding Explorer Robot (PUFFER) and Cooperative Autonomous Distributed Robotic Explorer (CADRE). The results indicate that flexible systems can be significantly impacted by a non-Gaussian excitation profile and that neither a typical enveloping of a Gaussian excitation nor a superposition of the responses to a worst-case impulse load with the response to a Gaussian signal was sufficient to bound the response due to non-Gaussian excitation. The driving mechanism for increased sensitivity of flexible robotic systems appears to be inertial, and designers may consider shifting the relative flexibility of the system or its constraints to force particular deformation modes or designing hinge mechanisms with increased damping to minimize the influence of non-Gaussian signals on the response of a flexible robotic structure.

On-site calibration method for a binocular vision sensor based on the phase-shift algorithm.

When a binocular vision sensor (BVS) is installed in a narrow space, traditional calibration methods are limited as all targets should be placed in more than three different positions. To solve this problem, an on-site calibration method based on the phase-shift algorithm is proposed in our paper. Intrinsic parameters of these two cameras should be first calibrated offline. Series of phase-shift patterns are projected onto any one target with known three-dimensional information to determine the relationship between two cameras. The target utilized in our proposed method can be selected arbitrarily, which is suitable to achieve the on-site calibration of BVS, especially in industrial vibration environments. Experiments are conducted to validate the effectiveness and robustness of our proposed method.

Eco-friendly, compact, and cost-efficient triboelectric nanogenerator for renewable energy harvesting and smart motion sensing

In recent years, the growth of Internet of Things devices has increased the use of sustainable energy sources. An alternative technology is offered by triboelectric nanogenerators (TENGs) that can harvest green energy and convert it into electrical energy. Herein, we assessed three different nopal powder types that were used as triboelectric layers of eco-friendly and sustainable TENGs for renewable energy harvesting from environmental vibrations and powering electronic devices. These nanogenerators were fabricated using waste and recycled materials with a compact design for easy transportation and collocation on non-homogeneous surfaces of different vibration or motion sources. In addition, these TENGs have advantages such as high output performance, stable output voltage, lightweight, low-cost materials, and a simple fabrication process. These nanogenerators use the contact-separation mode between two triboelectric layers to convert the vibration energy into electrical energy. TENG with the best output performance is based on dehydrated nopal powder, generating an output power density of 2.145 mWm−2 with a load resistance of 39.97 MΩ under 3g acceleration and 25 Hz operating frequency. The proposed TENGs have stable output voltages during 22500 operating cycles. These nanogenerators can light 116 ultra-bright blue commercial LEDs and power a digital calculator. Also, the TENGs can be used as a chess clock connected to a mobile phone app for smart motion sensing. These nanogenerators can harvest renewable vibration energy and power electronic devices, sensors, and smart motion sensing.

Vibration reduction of human body biodynamic response in sitting posture under vibration environment by seat backrest support.

Four-degree-of-freedom (4-DOF) human-chair coupling models are constructed to characterize the different contact modes between the head, chest back, waist back and backrest. The seat-to-head transfer ratio (STHT) is used as an evaluation metric for vibration reduction effectiveness. The simulated vibration reduction ratio of the model is close to the experimental results, which proves the validity of the model. The peak STHT is obviously reduced (P < 0.05, T-test) with seat-backrest support. The experiments show that supporting the head ( , P < 0.05, Wilcoxon matched-pairs signed ranks) has the best vibration reduction effect (21%), supporting the chest back ( , P < 0.05) has a reduced effect (11%), and supporting the waist back ( , P < 0.05) has the weakest effect (4%). When the upper torso is in full contact with the backrest, the peak STHT curve and resonance frequency are positively correlated with the contact stiffness of the seat surface and negatively correlated with the contact damping. In order to reduce the seat-to-head transfer ratio, the lowest STHT peak and lowest total energy judgments were proposed as the selection methods for the selection of the contact stiffness and damping of the backrest in two environments (periodic and non-periodic excitation), respectively.

Construction of environmental vibration prediction model for subway transportation based on machine learning algorithm and database technology

Vibrations generated in the metro transport environment are mainly caused by, vibrations generated by the interaction between the metro and the track during operation. and the change of vibration factors will affect the normal operation of the subway. However, it is difficult to have a model that can achieve the characteristics of high accuracy, fast computing speed and wide range of use in the traditional metro rail transportation environment prediction. Therefore, this research uses database theory and machine learning algorithms to predict the vibration of subway transportation environment. The experimental results show that the average difference between the whole prediction value and the real value is 1.4 dB, of which the maximum difference error value is 0.29%, the maximum error difference is 8.2%, and the approximate value is 6.2 dB, and the four averages predicted in 40 m are relatively small as 1.6 dB, and the average error value of prediction ability between 40 and 100 m is 1.72 dB, and the experimental prediction value and real value are in good agreement. The agreement between the experimental prediction and the real value is very good. Therefore, the model is able to predict the vibration model of the subway transportation environment with a high degree of agreement and accuracy.

Modified time domain randomization technique for multi-shaker non-stationary non-Gaussian random vibration control

Traditional random vibration environmental tests simulate stationary Gaussian random vibration environments. In this work, the generation and closed-loop control of multi-shaker non-stationary non-Gaussian random vibration signals with the modified time domain randomization technique are studied. The amplitude modulation function is introduced to control the non-stationary and non-Gaussian characteristics that the root mean square value of the generated signal changes with time. The kurtosis relationship between the one frame pseudo-random signal and consecutive true random signal is derived theoretically. It is found that the kurtosis of the consecutive non-stationary random signal is determined by the amplitude modulation function and kurtosis of the pseudo-random signal. The standard deviation of the time-varying root mean square reflects the non-stationary characteristics of the generated signal. A control strategy for multi-shaker non-stationary non-Gaussian random vibration environmental test is proposed. The non-stationary and non-Gaussian characteristics are extracted from the measured response signals so that the power spectral densities, kurtoses and non-stationary characteristics can be controlled simultaneously. The results from the simulation examples and multi-shaker vibration experiments prove the feasibility and practicability of the proposed non-stationary non-Gaussian random signal generation method and control strategy.

An investigation into vibration transmission patterns within metro turnout areas utilizing the structural sound intensity method

Urban rail transit turnout areas are notorious for inducing elevated environmental vibrations due to the complex interactions between wheels, rails, and supporting infrastructure. This paper establishes a comprehensive vehicle-track-tunnel-soil coupled dynamic model of a train traversing a turnout region. The intricate vibration transmission mechanisms within the turnout are explored through numerical simulation and visualization of vibration energy flow pathways. The structural sound intensity method facilitates the directional characterization of both transverse and longitudinal elastic waves emanating from the wheel-rail contact zone. Results reveal distinct propagation patterns between the switch panel and crossing panel, with more pronounced low-frequency energy backflow occurring in the switch panel. The transverse wave is found to dominate the elevated lateral vibrations observed along the tunnel walls. Frequency domain analysis maps the variation in energy flow directionality across one-third octave bands. The findings align closely with field measurement outcomes, validating the capacity of the approach to identify vibration "hot spots." Overall, this research enhances the theoretical comprehension of the complex interplay between diverse factors influencing turnout vibration transmission dynamics. The visualization technique proves instrumental in elucidating the critical mechanisms underlying the exacerbated environmental impact within these structurally intricate domains. Practical insights are distilled regarding turnout design strategies, vibration monitoring, and control methodologies to facilitate the mitigation of detrimental vibration effects.

Fractal-inspired multifrequency piezoelectric energy harvesters

In this Letter, we propose fractal-based piezoelectric energy harvesters (PEHs) for broadband energy scavenging. The introduction of fractal topology into transducers significantly alleviates the inherent limitation of a narrow working bandwidth in commonly used cantilever PEHs. We conduct a finite element analysis and experiments to exploit the performance of fractal cantilever PEHs with different iteration times. Our findings reveal that the higher-order fractal structures generate an increased number of eigenfrequencies as well as modal patterns within a certain range of working bandwidth (i.e., &amp;lt;50 Hz). Experimental results indicate that the efficient energy harvesting bandwidth of the fractal PEHs of iterative levels 1 and 2 is 2.05 and 2.15 times, respectively, larger than the conventional PEHs (i.e., level 0). In addition, the harvested voltage and power of fractal PEHs can be enhanced by attaching a proof mass to compensate for the energy loss in producing iterations. This method exhibits superiority over capturing energy in low-frequency vibration environments, such as wave energy and human movement energy.

Numerical investigation of solder joint shape for micro-spring package during vacuum vapor phase soldering

The novel micro-coil spring package has become a new choice for reliable applications in extreme temperature change, high-strength impact, long-term vibration and other harsh environments due to the advantages arising from its special packaging design. The study of solder joint shape is an important step in the characterization of the package reliability. By Ansys Fluent software, the finite volume method was applied to investigate the flow behavior of molten solder during vacuum vapor phase soldering and the volume of fluid model was used to track the solder melt front. The simulation results reveal the effect of two critical process parameters (solder volume and pad diameter) on solder joint shape in micro-spring array package. The fillet height of the solder joint increases with decreasing pad diameter and decreases with decreasing solder volume. The optimal solder volume is 0.07 mm3 coupled a pad diameter of 0.80 mm, producing suitable fillet height and nice concave fillet shape, which is in agreement with the real sample of micro-spring soldering joint. The good consistency between experiment and simulation proves that the finite element method can effectively predict the shape of the melted solder. This work paves the way for the optimization of the solder joint shape in the electronic assembly.

IoT-Machine Learning-Based Structural Health Monitoring System for Detection of Cracks in Bridges

The deteriorating condition of infrastructure, particularly bridges, poses significant challenges to public safety and necessitates the development of advanced monitoring systems for early detection of structural defects. This paper proposes a novel approach by integrating Internet of Things (IoT) technology with machine learning (ML) algorithms for real-time structural health monitoring, focusing on the detection of cracks in bridges. The proposed system employs a network of IoT sensors strategically deployed on the bridge structure to collect diverse data related to environmental conditions, strain, and vibrations. These sensors provide a continuous stream of data, creating a comprehensive dataset for analysis. Machine learning algorithms, specifically designed for anomaly detection, are applied to this dataset to identify patterns indicative of potential structural issues. This system is designed and implemented using ML and IoT. The excitation results shows that the designed system accuracy and efficiency of crack detection is improved and further enhance overall structural resilience. Furthermore, the integration of a real-time alerting mechanism allows for immediate notification of detected anomalies.