High Frequency Vibration Measurement Research Articles

Study on Temporary Unloading for Chatter Vibration Suppression Using Fixed Superabrasive Polishing Stone with Five-Joint Closed-Link Small Robot and Voice Coil Motor Thrust Control

In this study, an existing superfinishing method used for polishing glass surfaces was refined using a five-joint closed-link compact robot with fixed abrasive grains. In previous studies, a voice coil motor was used to control the constant-pressure pressing force while maintaining the polishing force for a relatively short period. However, maintaining the polishing force for long periods is imperative for achieving a high-quality polished surface. Thus, in this study, a strain gauge load cell was adopted in addition to a conventional piezoelectric force sensor to maintain the polishing force for a long period. First, the amounts of DC drift of the piezoelectric force sensor and strain gauge type load cell were compared to confirm the necessity of signal processing as well as the compatibility of long-term force measurement and high-frequency vibration measurement by application. Further, a method was proposed in which the change in the pressing force was recorded from the connected sensor; when the pressing force fluctuated, chatter vibrations were determined to occur, and the pressing force was temporarily set to 0 N. This method could obtain a better polished surface than the proportional-integral-differential (PID) control, which simply controls the pressing force at a constant value. Finally, chatter vibrations could be determined by detecting high-frequency sounds using a sound level meter. Notably, a finely polished surface could be obtained.

A medium-high frequency FBG accelerometer based on a V-shaped flexible hinge

Acquiring medium- and high-frequency acceleration signals is vital for broad infrastructure health monitoring, such as bridges, railways, and tunnels. This article introduces an innovative fiber Bragg grating (FBG) accelerometer featuring a V-shaped flexure hinge structure with enhanced sensitivity. Theoretical calculation and simulation analysis software were employed to evaluate the proposed structure's parameters. Experimental results show a sensitivity of approximately 67.9 pm/G under a working bandwidth of 400–900 Hz and a resonant frequency of 1250 Hz. The influence of temperature at 8.4 pm/°C and transverse interference validate 3.5%. These findings align with simulations, affirming the sensor's performance. This innovation holds promise for enhancing structural integrity monitoring in large-scale structures by detecting medium- and high-frequency vibration measurements.

A fiber Bragg grating acceleration sensor based on a circular flexure hinge structure for medium- and high-frequency vibration measurements

A fiber Bragg grating acceleration sensor based on a circular flexure hinge structure for medium- and high-frequency vibration measurements

Gain Spectrum Engineering in Slope-Assisted Dynamic Brillouin Optical Time-Domain Analysis

Slope-assisted Brillouin optical time domain analysis (SA-BOTDA) is a fast and distributed sensing technique that interrogates the Brillouin gain spectrum (BGS) near the middle of the linear region of its slope, allowing the measurement of high frequency vibrations. However, environmentally-induced deviations of the interrogation point from the rather small linear region around the optimum frequency position, result in harmonic distortion and changes in the slope value, which determines the gain-to-frequency conversion factor. Engineering the BGS by adding a loss probe, we propose a novel and improved version of SA-BOTDA, having a significantly wider drift tolerance for the interrogation point. Here, using a 14 ns pump pulse and a judicious choice of the frequency of the loss probe, we demonstrate an engineered BGS having a 70% wider frequency range (as compared with the conventional BGS), where the interrogation point can drift without compromising either the prescribed level of harmonic distortion or the given slope tolerance, further benefiting the flexibility and usage of SA-BOTDA.

Estimation of absolute distance and high-frequency vibration from the modulated SM-OFI signal using compound mutated genetic algorithm

Contactless measurement of absolute distance or high-frequency vibration is a prominent factor for many industrial & scientific applications like predictive maintenance, non-destructive testing, and reverse engineering, etc. In recent years, self-mixing optical feedback interferometry (SM-OFI) has proven its superiority over other conventional optical methods because of its simple, compact and less expensive structure. Typically, the extraction of the sensing parameters from the modulated SM-OFI signal relies on the analysis of interferometric fringes that often leads to a non-optimal solution for weak feedback conditions. In this paper, the authors introduce a novel method to process the SM-OFI signal that employs a multi-objective compound mutated genetic algorithm to search for optimum solutions. To the author's knowledge, this is the first attempt to measure the vibrating frequency and the absolute distance between the laser-diode front facet and the vibrating target, simultaneously using a multi-objective global optimization method instead of frequency analysis. The validity of the proposed method was experimentally tested on a vibrating object located 2 to 20 cm away from the laser diode and having a vibration frequency between 2 and 10 kHz. The proposed method exhibits an excellent accuracy of 1% & 0.98% with an SNR of 42 dB & 19 dB for absolute distance & vibration-frequency measurement, respectively. The method also possesses a resolution of 0.6 mm during absolute distance measurement and a percentage of error ranging between 2.3 to 8% during high-frequency vibration measurement, both under the weak feedback conditions. The comparison with other methods also supports the potential of the proposed method for the applications where absolute distance and frequency of the vibrations are required to measure simultaneously.

Measuring System of Vibration Diagnostic with the Metrological Self-Control Function

In the article, there is given the description of the method of metrological self-control in the measuring system of vibration diagnostic, the structural system of scheme is shown and the peculiarities of its functioning is self-control mode are given. The diagnostic methods, discussed in the article, usually are not completely independent and show the bigger effectiveness in the combined usage. The following problem exists: in the early stages of the appearing of a defect the informative components of vibration signals have extremely small amount of the energy and are covered with the background noise. Therefore, the effective method of the signal processing should assume the extraction of the informative signs of a damage when the signal/noise ratio is less than 1. Currently the biggest interest is presented by the group of the time frequency methods because they allow localizing in time the peculiarities of a vibration signal, therefore, they are potentially more sensitive to occurring defects than the time and spectral methods. Among their disadvantages are the mathematical complexity and the complexity of the realization and the interpretation of the results. The main advantage of developing system is the presence of the high frequency vibration measurement channel and also the built-in functional self-diagnosis system which principle is experimentally confirmed.

PM-PCF 기반 편광 간섭형 진동 센서의 주파수 응답에 관한 연구

In this paper, we investigated the frequency response of polarimetric vibration sensors based on polarization-maintaining photonic crystal fiber(PM-PCF). The proposed vibration sensor is in the form of a polarization-diversified loop configuration consisting of a polarization beam splitter, PM-PCF and two waveplates. A laser diode and a photodetector were used for high frequency vibration measurement. The PM-PCF lengths used in the experiments were 3.0, 6.5, 11.6cm, respectively and the effect of senosr head length on the frequency response of the sensor was investigated. The sensor head was attached to the piezoelectric transducer and single-frequency vibration in the range of 1-3000Hz was applied to it. In the fabricated vibration sensor, the measured resonance frequency was all the same at ∼400Hz and cut-off frequencies were measured as ∼2720, ∼1970 and ∼1550Hz for 3.0-, 6.5-, and 11.6-cm-long PM-PCF, respectively. That is, the shorter sensor head not only increases the 3dB bandwidth, but also can be a suitable solution for localized sensing and sensor miniaturization. In addition, it is also expected to contribute to the detection of high frequency vibration.

3D vibration measurements by a virtual-stereo-camera system based on a single low frame rate camera

A 3D full-field optical system for high frequency vibration measurement is proposed. The system is composed of a single low-frame-rate camera and two planar mirrors. This compact optical setup overcomes the typical drawback of capturing synchronous acquisitions in the case of a camera pair. Moreover, planar mirrors allow for the use of the classical pinhole model and, thus, conventional stereo-calibration techniques. The use of a low-frame-rate camera provides on the one hand a high-resolution sensor with a relatively low-cost hardware but imposes, on the other, the adoption of a down-sampling approach, which is applicable only when a single (known) sinusoidal load is applied to the structure. The effectiveness of the proposed setup has been verified by the 3D vibration measurement of two different targets up to a frequency of 1 kHz, corresponding to a displacement amplitude of 0.01 mm.

Non-uniformly periodical sampling in phase-sensitive OTDR

The maximum detectable frequency response of phase-sensitive optical time domain reflectometry is limited by the sensing fiber length, which is a challenging issue in long-haul distributed vibration sensing. The vibration measurement in φ-OTDR system can be regarded as a discrete sampling process, and the sampling rate is the repetition rate of probe pulses. In this paper, we propose a method to enhance the detected frequency response range of φ-OTDR system by using non-uniformly periodical sampling, which is known for the ability of sub-Nyquist sampling for band-limited signals. The non-uniformly periodical probe pulses are injected into the sensing fiber to sample vibrations on the fiber. Experimental results show that the maximum detected frequency response is 2.3 kHz with ∼2397 Hz averaging frequency. The system can realize high frequency vibration measurement with low repetition rates of probe pulses in long-haul vibration measurement.

Digital Image Correlation Based on Projected Pattern for High Frequency Vibration Measurements

The dynamic characterization of mechanical components is a crucial issue in industry, especially in the field of rotating machinery. High frequency loads are typical in this field and experimental tools need to fulfill severe specifications to be able to analyze these high-speed phenomena. In this work, an experimental setup, based on a Digital Image Correlation (DIC) technique with a projected speckle pattern, is presented. The proposed approach allows the measurement of vibrational response characterized by a single sinusoidal component having a frequency up to 500Hz and an amplitude lower than 10μm.

Interferometer with bismuth silicon oxide crystal for vibration measurement

We present a small-amplitude, high-frequency vibration measurement system. This system is based on the reflective holographic grating in a crystal of bismuth silicon oxide without applying an external electric field. A quarter-wave plate is applied in the reference beam path, with a polarizer after the crystal, to fulfill the quadrature condition when no electric field is applied to the crystal. A reflection configuration is used to obtain a good overlapping of the interference beams, which increases the beam coupling. The factors that affect the diffraction efficiency, including the signal-to-reference-beam intensity ratio and the recording angle, has been investigated. The experimental results coincide with the theoretical results, and the optimal conditions are obtained. The results of comparisons of our system with the vibrometer TEMPO show that the nanometer vibrations of a piezoelectric transducer can be reliably detected.

Dynamic fiber Bragg grating sensing method

The measurement of high frequency vibrations is important in many scientific and engineering problems. This paper presents a novel, cost effective method using fiber optic fiber Bragg gratings (FBGs) for the measurement of high frequency vibrations. The method uses wavelength matched FBG sensors, with the first sensor acting as a transmission filter and the second sensor acting as the sensing portion. Energy fluctuations in the reflection spectrum of the second FBG due to wavelength mismatch between the sensors are captured by a photodiode. An in-depth analysis of the optical circuit is provided to predict the behavior of the method as well as identify ways to optimize the method. Simple demonstrations of the method were performed with the FBG sensing system installed on a piezoelectric transducer and on a wind turbine blade. Vibrations were measured with sampling frequencies up to 1 MHz for demonstrative purposes. The sensing method can be multiplexed for use with multiple sensors, and with care, can be retrofitted to work with FBG sensors already installed on a structure.

New deep groove ball bearings high frequencies vibration testing

The rolling bearing is a multi-body rotating system with rolling elements, inner, outer rings and cage transmitting motion and load from rotor to the bearing supports and machine body. The existence in the new bearing elements of micro-defects (surface roughness Rz, Rzmax, waviness Ws and of size rolling elements) generate stochastic high frequency vibration. It is important for manufacturing technology to examine quality of new bearings elements. This paper considers a new deep groove ball bearings single row 6205 2RSL C3/P6 experimental vibration testing method for quality assessment of new bearing separating micro-defects in inner raceway from micro-defects in outer races. This method is based on high frequency vibration measurements of lubricated and dry bearings with varied loads. DOI: http://dx.doi.org/10.5755/j01.mech.20.3.6740

An impact excitation system for repeatable, high-bandwidth modal testing of miniature structures

Recent advances in various micro-manufacturing techniques have enabled utilization of miniature devices in numerous applications. However, testing, modeling, and predicting performance of these structures still poses various challenges. Experimental modal analysis techniques have been widely used to obtain the dynamic characteristics of structures; however, having very high natural frequencies, small vibration amplitudes, and high compliance, miniature structures require additional care during modal testing. Although recent developments in sensor technology enabled to obtain accurate high frequency vibration measurements during modal testing of miniature structures, excitation of miniature structures without any damage and within high frequency range in a reproducible manner is still being investigated. This paper presents design, development, and performance evaluation of a custom-made impact excitation system that enables repeatable, high bandwidth, single-hit impacts, and controllable impact force for modal testing of miniature structures. The system is equipped with a miniature force sensor attached to a custom designed flexure and an automated release mechanism driven by an electromagnet. The excitation bandwidth and the impact force exerted to the test structure can be controlled through control parameters: initial displacement given to the flexure and gap between the impact tip and the test surface.

118304 打撃試験を用いた高周波帯域の特性変動検知に基づくボルトの緩み診断(一般02 機械力学・制御工学3)

118304 打撃試験を用いた高周波帯域の特性変動検知に基づくボルトの緩み診断(一般02 機械力学・制御工学3)

Loose Bolt Detection by High Frequency Vibration Measurement with Non-Contact Laser Excitation

This paper proposes a vibration testing and health monitoring system based on an impulse response excited by a laser ablation. High power YAG pulse laser is used for producing an ideal impulse force on structural surface. It is possible to measure high frequency vibration responses in this system. A health monitoring system is constructed by this vibration testing system and a damage detecting algorithm. A microscopic damage of structures can be extracted by detecting fluctuations of high frequency vibration response with the present health monitoring system. In this study, loosening of bolt tightening torques is defined as the damage of the system. The damage is detected and identified by statistical evaluations of measured frequency response data with Recognition-Taguchi method. The effectiveness of the present approach is verified by experiment to detect and identify the loosening of bolts installed on an aluminum block structure.

Health Monitoring Based on High Frequency Vibration Measurement with Laser

This paper proposes a vibration testing and health monitoring system based on an impulse response excited by a laser ablation. High power YAG pulse laser is used in this system for producing an ideal impulse force on structural surface. It is possible to measure high frequency vibration responses in this system. A health monitoring system is constructed by this vibration testing system and a damage detecting algorithm. A microscopic damage of structures can be extracted by detecting fluctuations of high frequency vibration response with the present health monitoring system. In this study, loosening of bolt tightening torques is defined as the damage of the system. The damage is detected and identified by statistical evaluations of measured frequency response data with Recognition-Taguchi method.

203 レーザー加振技術を用いた高周波振動計測に基づくヘルスモニタリング(セッション5 スマート構造システム(1))

203 レーザー加振技術を用いた高周波振動計測に基づくヘルスモニタリング(セッション5 スマート構造システム(1))

A04 レーザーによる高周波振動計測に基づくヘルスモニタリング(OS5 スマート構造システム)

This paper proposes a vibration testing and health monitoring system based on an impulse response excited by a laser ablation. In conventional vibration testing using an impulse hammer, the excitation force hardly includes high frequency element over tens of kilohertz. High power YAG pulse laser is used in this system for producing an ideal impulse force on structural surface. It is possible to measure high frequency FRF (Frequency Response Function) in this system. And water droplet overlay on the metal is used to adjust the force magnitude in laser excitation. A health monitoring system is constructed by this vibration testing system and damage detecting filter. A microscopic damage of structures can be extracted by detecting fluctuations of high frequency vibration response with this health monitoring system. The vibration testing system is validated by comparing an aluminum block's FRFs that are obtained by laser excitation, impulse hammer and FEM.

A wave propagation and vibration-based approach for damage identification in structural components

A damage index (DI) approach for damage detection and localization based on high frequency wave propagation data and low frequency vibration measurements is presented. Improved ultrasonic and vibration test setups, consisting of either distributed high-fidelity piezoelectric sensor arrays or laser vibrometer, data acquisition boards, signal conditioning and dedicated software have been implemented. In the wave propagation measurements, the data consist of broadband signals due to ultrasonic waves propagating in the structure, while in the vibration measurements they are modal response of the structure produced by the actuators. Using the initial measurements performed on an undamaged structure as baseline, damage indices are evaluated from the comparison of the frequency response of the monitored structure with an unknown damage. In case of wave propagation measurements, a damaged/undamaged path mechanism is used to approximately locate the damage using the correlations obtained between the statistical DI (statistic t) values at the sensor locations (control points). For vibration measurements, both piezoelectric patches and the laser vibrometer are used as response sensors in an effort to examine their sensitivity to damage detection. It is found that the laser vibrometer acquisitions produce improved sensitivity and higher accuracy of the DI when compared to piezo-patches as response sensors. In addition, Modal Assurance Criterion (MAC) has been used to compare and quantify the changes in the modal parameters evaluated from the measurements carried out on the healthy and damaged structure. The DI approach is used to identify various types of defects in the form of loose rivet holes, delaminations due to low velocity impact and added mass for changes in the stiffness, in both metallic and composite structural components with relatively complex geometries. It is shown that the procedure is able to identify an emerging and/or growing defect, with some degree of confidence.