Multiple Vibration Research Articles

The enhancement of fault detection for rolling bearing via optimized VMD and TQWT based sparse code shrinkage

A typical vibration signal of fault bearing is composed of periodic repetitive transient impulses, multiple vibration disturbance and background noise. Variational mode decomposition (VMD) represents a potential tool for analyzing such signals. However, the reasonable selection of VMD algorithm parameters hinders its application in mechanical signal processing to a certain extent. According to the specific characteristics of rolling bearing fault signal, the composite dimensionless index is constructed as the objective function to ensure the optimal decomposition of VMD. To further enhance the fault characteristics, the tunable Q-factor wavelet transform (TQWT) along with sparse code shrinkage is proposed to denoise the modal components containing periodic impulses, which further highlights the impulses and improves the sparseness of fault signal. Simulation and experimental signal analysis verify the effectiveness and reliability of this method. The results show that the use of optimized VMD and TQWT based sparse code shrinkage dramatically sharpens the impulses from the mixed signal with noise interference and increases the sparseness to a level.

Vibration load identification in the time-domain of high arch dam under discharge excitation based on hybrid LSQR algorithm

The identification of vibration load is of great importance in studying the vibration induced by discharge of high arch dam. Considering the ill-posedness in time-domain identification of vibration load, a hybrid least squares QR (LSQR) iterative identification method is proposed. The system response is expressed as the convolution of the unit impulse response function and the excitation load. It is discretized into a set of linear equations, and the mathematical model of the inverse problem of load identification is established. On the basis of vibration signal filtering and noise reduction, Tikhonov regularization method is used to pre optimize LSQR iterative algorithm. This process is performed because the LSQR algorithm is prone to nonconvergence when the error of observation data is large. Thus, a hybrid LSQR algorithm is obtained to improve the ill-posedness of the inverse problem. Numerical examples show that the proposed method can recognize multiple vibration loads effectively and stably under different noise levels, and the recognition accuracy is better than the conventional regularization method. The proposed method is applied to an engineering example. Results show that the proposed method is feasible and effective for the time-domain identification of vibration load of a high arch dam.

A novel ultrasonic transducer with multiple vibrations in microelectronic packaging

Ultrasonic wire bonding is a typical packaging for semiconductor devices. Compared with single longitudinal transducer, we propose a novel ultrasonic transducer with multiple vibrations for the microelectronic packaging. The transducer is designed to excite the longitudinal and bending vibration individually or simultaneously. By simulation calculation, three longitudinal vibrations and a bending vibration is attained in the same node flange. The transducer structure is established by optimizing a balance and a Z-shaped flange, which can achieve the optimal modal shape. Under the 10 kg·cm torque for clamping the piezoelectrics stacked, the frequency of longitudinal vibration is 64.8 kHz 103.4 kHz 142.8 kHz and bending vibrations is 70.5 kHz. A dual channel driver with Field Programmable Gate Array (FPGA) and Digital Signal Processing (DSP) controller is self-developed to excite the multiple vibrations. In experiment, each vibration is excited individually, switched or simultaneously. It is found that all vibration for each operating modes is higher than 1 µm, and the vibration profile can be controlled as a rectangle or parallelogram, which has potential to be a new bonding process.

Low-Frequency Vibration Control of Metro Slab Track Based on Locally Resonant Theory

Vibration control has always been one of the research hotspots in the field of urban metro system. Due to the unsatisfactory application effect of traditional vibration damping technology in practice, a novel method, based on the locally resonant theory, was introduced into metro vibration damping system to improve the low-frequency vibration reduction effect. Meanwhile, the new metro vibration reduction slab track was designed. Furthermore, the coupled model of the metro vehicle-slab track was established and verified, and the reduction effect of the new metro slab track on low-frequency vibration under the action of metro vehicles was analyzed. Results show that: 1) The new vibration reduction slab track is really in control of the low-frequency vibration (50–100 Hz), and the attenuation effect can reach 10 dB; 2) The new slab track has multiple low-frequency vibration band gaps, which can achieve multi-frequency vibration reduction; 3) The new slab track can reduce the vibration acceleration of the track, which can improve the comfort level of the vehicle. Therefore, the local resonance theory enriches the existing metro vibration reduction design theory and provides a method for the design of the metro vibration control.

AutoLoc: Autonomous Sensor Location Configuration via Cross Modal Sensing.

Internet-of-Things (IoT) systems have become pervasive for smart homes. In recent years, many of these IoT sensing systems are developed to enable in-home long-term monitoring applications, such as personalized services in smart homes, elderly/patient monitoring, etc. However, these systems often require complicated and expensive installation processes, which are some of the main concerns affecting users' adoption of smart home systems. In this work, we focus on floor vibration-based occupant monitoring systems, which enables non-intrusive in-home continuous occupant monitoring, such as patient step tracking and gait analysis. However, to enable these applications, the system would require known locations of vibration sensors placed in the environment. Current practice relies on manually input of location, which makes the installation labor-intensive, time consuming, and expensive. On the other hand, without known location of vibration sensors, the output of the system does not have intuitive physical meaning and is incomprehensive to users, which limits the systems' usability. We present AutoLoc, a scheme to estimate the location of the vibration sensors in a two-dimensional space in the view of a nearby camera, which has spatial physical meaning. AutoLoc utilizes occupants' walking events captured by both vibration sensors and the co-located camera to estimate the vibration sensors' location in the camera view. First, AutoLoc detects and localizes the occupant's footsteps in the vision data. Then, it associates the time and location of the event to the floor vibration data. Next, the extracted vibration data of the given event from multiple vibration sensors are used to estimate the sensors' locations in the camera view coordinates. We conducted real-world experiments and achieved up to 0.07 meters localization accuracy.

Adaptive Electromagnetic Vibration Absorber for a Multimode Structure

All structures experience vibrations due to external dynamic force excitations, such as earthquakes and wind loadings. At resonance, the impact of this natural dynamic force on structures may lead to structural failures. Hence, an absorber is mounted to absorb vibrations from the primary system. Unfortunately, passive tuned mass absorbers can only target a single frequency. Since structural buildings possess multiple modes, an adaptive or tune-able vibration absorber is needed to attenuate the vibration in a multi-degree of freedom (MDOF) system. In this work, an adaptive electromagnetic vibration absorber (AEMVA) is proposed to eliminate the effects of vibrations and is dynamically tuned using electromagnets. By varying the current supplied to the coil, the stiffness of the AEMVA can be adjusted, resulting in a varying absorber frequency. A mathematical description of the AEMVA on a three-story prototype model building is also presented. The three-story benchmark model was used to demonstrate the effectiveness of AEMVA in absorbing multiple vibration modes, both analytically and experimentally. It is shown that 68.81 %, 50.49 %, and 33.45 % of vibration amplitude reductions were achieved at the first, second, and third modes, respectively.

Study of the multi-excitation decoupling optimization method for the integrated structure of a high-resolution optical satellite

In this paper, the sensitive frequency band for distortion and blurring phenomena of the in-orbit satellite is studied and the results are supplements for existing studies and can provide an important reference for the study of micro-vibration. To contain the large-amplitude and micro-vibration excitation response in this sensitive frequency band, a multi-excitation decoupling optimization method is proposed for the integrated structure of high-resolution optical satellites. First, the equivalent dynamics models of the satellite with and without an vibration isolator are established. By deriving the functional relationship between satellite bus stiffness, vibration isolator stiffness, and vibration isolation efficiency, the design objectives can be decoupled and assigned to the vibration isolator and satellite bus in a more cost-effective way, respectively, while maintaining a low computation volume of the multi-objective and multi-variable system optimization. Then, the satellite system is optimized with the objectives of minimizing the large-amplitude vibration response in the launch phase and the micro-vibration response in the orbital operation phase using the NSGA-II genetic algorithm. Finally, the design is verified by ground experiments that it can fully achieve required technical parameters under multiple vibration excitations. This method has certain reference value for the design of complex structural systems of high-resolution satellites.

HapticProxy: Providing Positional Vibrotactile Feedback on a Physical Proxy for Virtual-Real Interaction in Augmented Reality

Consistent visual and haptic feedback is an important way to improve the user experience when interacting with virtual objects. However, the perception provided in Augmented Reality (AR) mainly comes from visual cues and amorphous tactile feedback. This work explores how to simulate positional vibrotactile feedback (PVF) with multiple vibration motors when colliding with virtual objects in AR. By attaching spatially distributed vibration motors on a physical haptic proxy, users can obtain an augmented collision experience with positional vibration sensations from the contact point with virtual objects. We first developed a prototype system and conducted a user study to optimize the design parameters. Then we investigated the effect of PVF on user performance and experience in a virtual and real object alignment task in the AR environment. We found that this approach could significantly reduce the alignment offset between virtual and physical objects with tolerable task completion time increments. With the PVF cue, participants obtained a more comprehensive perception of the offset direction, more useful information, and a more authentic AR experience.

Optimization of multiple tuned mass dampers for a two-span continuous railway bridge via differential evolution algorithm

The study aims at proposing a methodology for optimization of multiple tuned mass dampers (MTMD) in reducing the multi-resonance vibrations of continuous bridges due to moving train loads. The equations of motion for time-domain analysis are derived for obtaining train-induced vibrations of a two-span continuous railway bridge with equipped MTMD-1 and MTMD-2 devices when the vehicle-bridge interaction (VBI) is considered. The bridge and the train are modeled as a Bernoulli-Euler beam with constant section and a series of moving sprung masses of identical length, respectively. To reduce the multiple resonance vibrations of a two-span continuous railway bridge, the MTMD-1 and MTMD-2 are tuned to the first mode and the second mode of the bridge, and they are attached to the midspan of each span, respectively. The optimum parameters of the both MTMD systems are investigated using the differential evolution (DE) method. The criterion chosen to obtain the optimum parameters is the minimization of the first two resonance peaks of the bridge. The influence of the different mass ratios and the number of TMD units in the MTMD system on the optimum parameters of the both MTMD systems and corresponding displacement responses of the bridge are also investigated. The results show that the VBI effect does not have much effect on the resonant train speeds and the control performance of TMDs. Therefore, the optimum parameters of TMDs can be obtained quickly by modeling the train as a series of moving forces for the vibration control of railway bridges.

High-Accuracy Event Classification of Distributed Optical Fiber Vibration Sensing Based on Time-Space Analysis.

Distributed optical fiber vibration sensing (DVS) can measure vibration information along with an optical fiber. Accurate classification of vibration events is a key issue in practical applications of DVS. In this paper, we propose a convolutional neural network (CNN) to analyze DVS data and achieve high-accuracy event recognition fully. We conducted experiments outdoors and collected more than 10,000 sets of vibration data. Through training, the CNN acquired the features of the raw DVS data and achieved the accurate classification of multiple vibration events. The recognition accuracy reached 99.9% based on the time–space data, a higher than used time-domain, frequency–domain, and time–frequency domain data. Moreover, considering that the performance of the DVS and the testing environment would change over time, we experimented again after one week to verify the method’s generalization performance. The classification accuracy using the previously trained CNN is 99.2%, which is of great value in practical applications.

Multiple Periodic Vibrations of Auxetic Honeycomb Sandwich Plate with 1:2 Internal Resonance

In this paper, we focus on the multiple periodic vibration behaviors of an auxetic honeycomb sandwich plate subjected to in-plane and transverse excitations. Nonlinear equation of motion for the plate is derived based on the third-order shear deformation theory and von Kármán type nonlinear geometric assumptions. The Melnikov method is extended to detect the bifurcation and multiple periodic vibrations of the plate under 1:2 internal resonance. The effects of transverse excitation on nonlinear vibration behaviors are discussed in detail. Evolution laws and waveforms of multiple periodic vibrations are obtained to analyze the energy transfer process between the first two order modes. Even quite small transverse excitation can cause periodic vibration in the system, and there can be at most three periodic orbits in certain bifurcation regions. The periodic orbits are classified into two families by tracing their sources. The study provides the possibility for the classification study on generation mechanism of system complexity and energy transfers between different modes.

Polarization‐ and Angle‐Dependent Plasmonic Synchronous Fluorescence Spectroscopy to Probe Molecular Vibrational Couplings on an Aluminum Nano‐Film

AbstractProbing light−matter interactions at the nanoscale is essential for elucidation of their fundamentals and construction of novel nano‐optical devices. In this work, it is proposed that polarization‐ and angle‐dependent plasmonic synchronous fluorescence spectroscopy could be powerful to resolve UV–vis plasmon mediated molecular couplings, even under vibrational sublevels. Taking studies of polycyclic aromatic hydrocarbons (PAHs, one general class of graphene analogs with emission range of 350–550 nm) as demonstration, a simple but efficient device of PAHs nanolayer (with thickness in tens to hundreds of nanometers) on an Al nano‐film is fabricated. By synchronously scanning excitation and emission wavelengths in a high resolution to depict polarization‐ and angle‐dependent spectrographic profiles, the vibrational transitions coupled to the Al plasmons could be identified, while these could not be attained by conventional fluorescence measurement. As a result, the featured molecular vibrational couplings for both surface plasmon‐ and plasmonic waveguide‐mediated PAHs–Al interactions have been successfully observed at room temperature. Even toward crowded and overlapped spectral components containing multiple vibrations, the transitions could be individually distinguished. These efforts will contribute to the further exploitation and construction of efficient light‐emitting devices via luminant molecules on a metal surface.

Active Vibration Control on a Smart Composite Structure Using Modal-Shaped Sliding Mode Control

Abstract This article proposes an active modal vibration control method based on a modal sliding mode controller applied to a smart material composite structure with integrated piezoelectric transducers as actuators and sensors. First, the electromechanical coupled system is identified using a modal reduced-order model. The sliding surface is based on the modal-filtered states and designed using a general formulation allowing the control of multiple vibration modes with multiple piezoelectric sensors and actuators. The performance and stability of the nonlinear controller are addressed and confirmed with the experimental results on a composite smart spoiler-shaped structure. The nonlinear switching control signal based on the modal-shaped sliding surface improves performances of the linear part of the control while maintaining not only stability but also robustness. The attenuation level achieved on the target modes on all piezoelectric sensors starts from −14 dB up to −22 dB, illustrating the strong potential of nonlinear switching control methods in active vibration control.

Performance based design of a new hybrid passive energy dissipation device for vibration control of reinforced concrete frames subjected to broad-ranging earthquake ground excitations

This paper evaluates a new hybrid passive device that comprises two different passive energy dissipation categories, namely, viscoelastic damper and friction damper. The device operates as a synergic unit using a novel locking mechanism. The hybrid passive device offsets the drawbacks of individual devices and facilitates improving the performance of structures for multiple excitation vibration levels due to wind and seismic events. Both devices are connected in a parallel combination using locking mechanisms and exhibit distinct hysteretic characteristics under small and significant deformation. The viscoelastic damper alone will be activated for extreme winds and minor to moderate earthquakes, and both devices will work simultaneously for strong earthquakes. Considering the advantages of such a new device, this article presents a new seismic design method structures equipped with a hybrid passive dampers device using the energy-balance concept. The method accounts for the structural member's inelastic behaviour, phase transformation of the stiffness and the energy dissipation capacity of the energy devices to achieve the intended performance level under the design earthquake hazard. The proposed method has been applied on a six- and a twelve-storied reinforced concrete building. The seismic performance is verified through nonlinear time history analysis using a set of near and far-field ground motions. Numerical results are investigated in terms of the inter-story drifts, the residual drifts, the floor acceleration and the yield mechanisms. The structure's performance corresponds well with the target performance levels.

An improved multi-mode seismic vibration control method using multiple tuned mass dampers

Multiple vibration modes of an engineering structure might be excited by earthquake ground motions. Multiple tuned mass dampers (MTMDs) are widely used to control these multi-mode vibrations. However, in the commonly used MTMD system, the mass element in each tuned mass damper (TMD) is normally assumed to be the same. To improve the performance of MTMDs for seismic-induced vibration control, non-uniform MTMD masses are adopted in the present study to improve the mass utilization of TMD, and a location factor is proposed to determine the best location of each TMD in the MTMD system. The effectiveness of the proposed method is validated through numerical study. The results show that the proposed method effectively reduces the seismic responses of the structure induced by multiple vibration modes.

Torsional Vibration Reduction of Railway Vehicle Model by Controlling Internal Pressure of Air Springs using H-infinity Methods

As railway vehicles become faster and lighter, the vibration of carbody tends to increase and that makes the ride comfort worse. In lateral and vertical rigid-body vibration, a number of reduction technologies have been put into practical use, such as semi-active suspensions and variable vertical dampers installed between carbody and bogie. In elastic vibration, various methods have been studied, such as control by previously mentioned dampers, stack-type piezoelectric actuators. However, these methods focused on only the bending vibrations, it has been difficult to reduce multiple elastic vibration modes simultaneously. The authors propose a method to simultaneously reduce multiple elastic vibration modes, including torsional vibration, by controlling internal pressure of air springs. Since this method uses existing devices, it is superior in weight, cost, and maintenance compared to installing a new vibration compensator. First of all, we developed railway vehicle analytical model that can express elastic vibration including torsional vibration. Furthermore, we designed a control system by H-infinity methods and verified vibration-reduction effect on the stationary excitation test of simple railway vehicle model. As a result, it was confirmed that multiple elastic vibration modes, including torsional vibration, can be reduced simultaneously.

Transmission of Haptic Experience by a Bracelet-type Tactile Device to Reproduce Vibration Distribution

Recently, the demand for technology to remotely transmit haptic experiences related to skills has been increasing. This study attempts to convey a haptic experience with tactile sensation by reproducing the spatial patterns of vibrations generated at the wrist using a bracelet device with multiple sensors and vibrators. This paper investigates the human discrimination capability of haptic experiences during different whisking motions by comparing the bracelet device with a conventional tool-mounted device. We also investigate the effect of the ISM method, which can modulate the waveform to lower frequencies while maintaining the original sensation. The results indicated that reproduction of spatial distribution by bracelet device improves discrimination of differences in the rotation direction, and ISM further improves the discrimination of directional rotation compared to the raw signals.

多質点系磁歪式振動発電デバイスの最適設計

We are conducting research on the practical application of vibration power generation using magnetostrictive materials (Fe-Ga). The power generator, consisting of magnetostrictive material, U-shaped frame, coil and permanent magnet, has a simple structure and high output characteristics. However, vibration power generation is difficult to put to practical use because of the presence of environmental vibrations with multiple frequencies. The conventional generator is a single mass system, and when the frequency of the vibration source matches the resonant frequency of the generator, a large amount of power can be generated. For this reason, it is difficult to generate power efficiently when there are multiple vibration frequencies. Therefore, in this paper, we propose a generator for multi-mass point systems. The parameters are derived by optimization calculations to match the two natural frequencies of the generator to the target frequencies, and the evaluation of the power generation characteristics under real vibration is reported.

Dynamic compliance attenuation in ball screw drives through model-based active damping of multiple vibration modes

This paper presents a new control structure for ball screw drives (BSDs), which achieves position tracking through an outer loop, and active vibration damping for dynamic stiffness enhancement through an inner loop based on H2-synthesis. As an advancement over earlier BSD control methods with active damping, the proposed technique is able to consider multiple vibration modes simultaneously, rather than only the most dominant (axial) vibration mode. The end result is 2–3 times reduced dynamic compliance over a wide frequency range, compared to approaches like P-PI position-velocity cascade control (industry standard) and pole-placement control (PPC), and comparable or better tracking accuracy.

Weighted evenly peak reduction method for multimodal NC-piezoelectric shunt-damping

Piezoelectric NC-shunt damping is a technique for vibration suppression by connecting an external circuit called the NC-shunt circuit (Negative capacitor shunt circuit) to a piezoelectric element attached to a mechanical structure. In this paper, we develop the multimodal NC-piezoelectric shunt-damping by proposing a new cost function, which enables to evaluate the decreases in multiple resonance peaks equally. The proposed method takes the difference between the gain peak when uncontrolled and the gain peak when the selected NC-shunt circuit is used. It then selects the smallest of the multiple vibration modes and optimizes it to be larger. Numerical examples are demonstrated to evaluate the effectiveness of the proposed cost function. In addition, we investigate the gain diagrams of the open-loop transfer functions to clarify the key issues in the broad-band vibration control performance of the NC-shunt circuit. It is shown that the vibration control is effective if the anti-resonance and resonance frequencies of the open-loop transfer function are located between the bending points of the admittance.