Vibration Measurement Method Research Articles

Vibro-acoustic analysis of metal and non-metal gears used in a powertrain

Gearbox (Powertrain) is one of the prime sources of noise in any Automobile. The noise can be broadly divided into two types. First is the one that occurs due to meshing of gears and second due to the inefficient design of the gearbox casing. This paper focuses majorly on the former problem and compares the results for analytical methods of vibration measurement. Modal analysis is carried out on a 5-speed synchromesh manual gearbox using ANSYS to find out modes of vibrations. The amplitude of noise is then calculated for one specific modal frequency (the one showing maximum deflection) using Acoustics module of COMSOL Multiphysics Software for 4 different gear materials.

Vibration measurement technology based on the reverse point recognition algorithm for laser self-mixing interference.

The self-mixing interference (SMI) signal carries the information of the external moving object, which has great physical significance and application prospects for extracting and analyzing the information of the external object. In this paper, we propose a vibration measurement method based on a reverse point recognition algorithm on the SMI laser signal. By extracting and analyzing the hill and valley values of the SMI signal to determine the reverse point, combined with the semifringe counting method, the vibration information of external objects can be accurately extracted. The method we propose simplifies the displacement reconstruction process with high accuracy. The simulation and experimental results show that this method can achieve high-precision measurements of microvibration with an absolute error of less than 19 nm.

교통사고 차량 운전자의 인체 진동 측정 방법 및 평가 기준에 관한 연구

In a traffic accident, scientific data are needed to refute the driver's false claim or statement that the shock was not recognized at the time of the accident. ISO2631 deals with methods and evaluation criteria for measuring human vibration of vehicle occupants. In this study, we tried to find out the characteristics of human body vibration transmitted to vehicle occupants on comfort. In evaluating the impact of unpaved roads or speed bumps on vehicle drivers in future traffic accident site investigation, it is expected that objective evaluation can be performed by utilizing the human vibration measurement method, evaluation criteria, and experimental values performed in this study.

Research on high-temperature vibration measurement method using laser Doppler interferometry

High-temperature vibration measurement plays a critical role in the design and performance testing of equipment such as aero-engine and heavy-duty gas turbines. Due to its non-contact, high accuracy, and resolution, the laser Doppler method has become one of the most commonly used vibration measurement techniques. However, one of the main problems in high-temperature vibration measurement is that the surface of the measured objects is oxidized, thus resulting in a decrease of interference signal intensity and signal-to-noise ratio. Furthermore, the aforementioned may even cause measurement failure. In this paper, an all-fiber laser Doppler velocity measurement device using a fiber optic circulator is established. Its vibration measurement performance is experimentally validated at high temperatures. The results demonstrate that this device can achieve vibration measurement within the temperature range of 300°C-1200°C with a maximum vibration speed of 1 m/s and maximum vibration acceleration of 378.4 m/s2. Relative deviation with Polytec vibrometer’s velocity results is within 1.95%. This model provides a viable solution for achieving accurate measurements of high-temperature vibration.

Full-field laser heterodyne imaging vibrometry using a CMOS-DVR system.

A laser heterodyne imaging vibrometry is proposed for full-field vibration measurement. The vibration responses are imaged and recorded using a CMOS camera and a digital video recorder. A digital demodulation method based on a cumulative distribution function and autocorrelation is designed to demodulate signals affected by speckle noise. The experimental investigations confirm the viability of the proposed method for vibration measurement. Meanwhile, a comparison with laser Doppler vibrometry is performed to further validate the method. The results prove the proposed vibrometry is an effective and precise option for full-field vibration measurement.

Vibration measurement of a rotating cylindrical structure using subpixel-based edge detection and edge tracking

Acceleration sensors are commonly used for measuring the vibrations of structures. However, these contact-type sensors cannot be installed in some areas, such as on objects located in hazardous areas. Recently, non-contact-type measurement approaches, including photogrammetry techniques (e.g., point tracking, digital image correlation, and target-less approaches) have been introduced using images obtained from cameras. Nevertheless, photogrammetric approaches, e.g., point tracking and digital image correlation, have the same problem because targets or high-contrast speckle patterns need to be mounted on structures. Instead, the target-less approaches for vibration measurement were developed and tested on static structures like bridges and other civil structures. However, analysts have rarely focused on the rotating axis of cylindrical structures, which is a general component of the rotation-based renewable power generation system. Therefore, in this paper, we introduced a subpixel-based vibration measurement method for a cylindrical rotating structure based on the video images acquired from a non-contact sensor. The frames were magnified, and subpixel-based edges were detected in each frame of the video. Then, using the proposed edge tracking technique, the coordinates of the edges in a region of interest were tracked throughout the video for measuring the vibrations. The proposed edge tracking technique keeps the track of the edge locations in the previous frame as well as the locations in the pixels of the current frame. To show the effectiveness of the proposed method, two simulation datasets and one real dataset were constructed. For the simulation datasets, we generated videos by adding sinusoidal noises together with random noise in an image that contains a static cylindrical object. For the real dataset, a video of a rotating cylindrical object was acquired. The results obtained using the proposed method were compared with the results obtained using the existing multi-interval second-order differential edge detection technique and partial area-based technique. From the simulation datasets, vibrations related to both the single and multiple frequencies were effectively detected by applying the proposed method. The proposed method had the lowest root mean square error (RMSE) calculated with the reference data compared to the existing methods. In the real dataset, we could demonstrate that the proposed method could effectively detect the vibrations on the rotating axis of a cylindrical structure with the exact locations of the edges while removing the non-interest edges or false edges. Moreover, during the frequency analysis, the peaks of the proposed method results were at the same frequency at which the object was rotating. Therefore, the proposed method can be a useful solution to detect the vibration of rotating structures located in hazardous areas with uneven backgrounds and uneven brightness.

Experimental study on fault detection in roller bearing used in rolling mill industry

Rolling element bearings are extremely important components of rotating machines, and bearing defects can cause machines to fail. As a result, early detection of such defects, as well as the severity of damage while the bearing is in operation, may help to prevent machine malfunction and breakdown. Vibration is produced by defective bearings when no. of passes are increases to reduce down the thickness of raw materials and these vibration signals can be used to diagnose the problem. This article provides a summary of recent developments in bearing defect studies, as well as sources of vibration and vibration measurement methods in the time, frequency, and time frequency domains. An experimental setup has been established in this paper to determine roller bearing faults. The fault evaluation progress is extracted using the signal processing method. The results are presented as time series and FFT plots. Misalignment fault, Indentation event, Smoothened dent, Defects, and Damage growth state are the five-wear fault assessment events examined. The test lasts 480 hours and takes place at temperatures ranging from 68 to 78 degrees Celsius. After 480 hours of testing, it was discovered that the roller bearing is damaged due to a high wear rate, with amplitude of acceleration in the frequency domain of 32.51 m/s2 at fifth event. The amplitude of acceleration in the frequency domain is also found to be greater than the critical value of 30 m/s2. As a result, the state of the roller bearing after 480 hours is the damage growth state.

Vision vibration measurement based on coded illumination in a single frame

A vision-based mechanical vibration measurement method is presented and verified by experiments in this paper. The coded illumination is projected on the objects by a digital light processing projector with a digital micromirror device in it. The projection patterns are designed to be concentric. In one integration time of the camera, the projector is exposed several times, which embeds temporal information in the images. A single frame can be divided into subframes by separating the coded concentric patterns. The centroids of the coded concentric patterns are fitted, and the centroids are treated as virtual feature points with vibration information. The acquisition devices are common low-speed cameras, and they record the vibration whose frequency exceeds the camera frame rate. The temporal resolution is increased by 10 times, corresponding to the 400 Hz sampling frequency in the experiment. We can measure the vibration of multiple points with different sampling frequencies. The frequency measurement accuracy is in the subhertz level in low-frequency measurement, relative error is always slightly greater than 0.01 in high-frequency measurement, and the amplitude resolution is 130 µm.

A deep learning augmented vision-based method for measuring dynamic displacements of structures in harsh environments

In this paper, a deep learning augmented vision-based method (DAVIM) is proposed for measuring structural displacement in harsh environments. DAVIM incorporates deep learning-based algorithms that include a Convolutional Neural Network (CNN) and a Generative Adversarial Network (GAN) for more accurate and robust sensing of the dynamics of structural models in wind tunnel tests or full-scale field measurements. The proposed method is first validated through numerical test including a discussion on the efficiency of CNN and GAN in really harsh environments. This is followed by three different kinds of experiments involving periodic vibration tests, motion of an aeroelastic model in a wind tunnel test and field measurements to effectively validate the proposed method from practical applications perspective. The proposed DAVIM exhibits a robust and superior performance compared to the traditional sensors (e.g., a laser displacement sensor and an accelerometer) and the Vision based vibration measurement (VVM) method. This is particularly the case when measuring large displacements with rigid-body rotational components and in long-term field measurements.

Non-contact vibration sensor using deep learning and image processing

This paper proposes a non-contact vibration measurement method based on deep learning and image processing. The deep learning method is used to realize the automatic and efficient selection of effective pixels and the optical flow method is used to extract vibration signals to realize non-contact and targetless visual vibration measurement. In this study, a carbon plate board and aluminum C-beam structure were measured and verified under artificial and non-human excitation in a laboratory environment. Additionally, bridge and cable structures in an outdoor environment were selected as measurement targets to verify the reliability of the proposed method. This paper compares the experimental results of Canny and Sobel edge detection algorithms and deep learning methods to verify the efficiency of deep learning. The results demonstrate that our method is robust, even under real-world unfavorable conditions, meaning it can serve as a novel measurement method in the field of vibration measurement.

Micro Vibration Measurement with Microscopic Speckle Interferometry Based on Orthogonal Phase

A micro-device vibration measurement method based on microscopic speckle interferometry combined with orthogonal phase is presented. This method utilizes the approximate linear distribution characteristics of orthogonal points (points satisfying the condition that the initial phase difference equal to π/2) to quickly obtain the vibration information of the measured object. Compared with common optical measurement methods, this method does not require scanning imaging and can realize real-time full-field measurement. Moreover, the measurement principle and equipment is simple, so there is no need to introduce a stroboscopic light source or heterodyne device.

Theory and method of multi-point synchronous deformation and vibration measurement based on millimeter-wave sensing

Although accelerometer-, vision-, and laser-based sensing technologies are widely used in deformation and vibration measurements, the multi-point simultaneous deformation and vibration measurement of large-scale structures with high accuracy remains a challenge. Herein, we developed a novel technology for contactless deformation and vibration measurement using millimeter-wave (mmWave) linear frequency-modulated continuous wave radar, establishing the theory and method for multi-point simultaneous deformation and vibration measurement based on mmWave sensing. The principle of mmWave multi-point vibration measurement and a method of displacement extraction were systematically described using the baseband signal model of multi-target perception. We built a prototype of the proposed mmWave vibration measurement system and a platform for simulated vibration tests. The accuracy of the mmWave multi-point vibration measurement technology was verified and compared with that of laser displacement sensors. Using the prototype system, we conducted experiments on the multi-point synchronous vibration measurement and model identification of the slender hinged flexible rod structure of a certain aerospace equipment in China and then described the dynamic response monitoring of a large bridge structure. Results showed that the deformation and vibration measurement method based on mmWave sensing developed in this work could conveniently and accurately extract the time domain information of multi-target vibration displacements. Our work provides an innovative method and approach for non-contact multi-point synchronous deformation and vibration measurements that could be applied to the mechanical performance test and health monitoring of large structures.

GIS vibration test method and characteristic signal recognition

Based on the characteristics of GIS insulation and mechanical fault types and practical measurement experience, two typical vibration measurement methods, direct measurement method and natural frequency measurement method, are proposed in this paper. Then, based on the real data of experiment and field measurement, the vibration signals of typical insulation fault and mechanical fault such as spike discharge and end cover looseness are compared, analyzed and summarized, and their respective data characteristics are extracted, which can provide the basis for the determination of GIS vibration fault types.

Three-dimensional vibration measurement method for lightweight beam based on machine vision

Three-dimensional vibration measurement method for lightweight beam based on machine vision

Detecting Vibration Problems in Machines and Structures Using Motion Capturing by Camera

Vibration in rotating machines and structures is normally measured using accelerometers and other vibration sensors. For large machines and structures, the process of collecting vibration data is tedious and time-consuming due to the large number of points where vibration data must be measured. In this paper, a novel non-contact vibration measurement method has been introduced by using a high-speed camera as a vibration measurement device. This method has many advantages compared with the others. It has a low cost, easy to setup, and high automation. It also can be used for full-field measurement. Many tests have been accomplished to prove the validation of this method. The verification test has been accomplished by using the machinery faults simulator. It presented a reasonable validation that the operation deflection shapes (ODS) and the phase difference of any object can be successfully measured by using a high-speed camera. The mode shape tests have been accomplished by using the whirling of shaft apparatus device to extract the time domain, frequency domain, ODS, and phase differences for many points on the shaft at the first two critical speeds. The results proved that the high-speed camera can be used to detect the vibration signal in many different fault cases. It also proved that the high-speed camera can be used to detect the ODS and the phase angle difference. That gives the proposed method more robust and acceptance.

Image-based method for the angular vibration measurement of a linear array camera.

Measurements of angular vibration of aerial cameras in a variety of operating conditions are critical to analyze the performance of the vibration isolation system. Instead of using an additional optical system to measure the angular motion of the camera, an image-based and easy-to-implement method is proposed for the linear array camera to measure the image motions captured by the camera directly. The natural frequencies of the vibration isolation were also measured by laboratory vibration test. For image vibration measuring, the angular vibration is represented in image motion by the relationship between the image motion and angular motion of the camera. Based on the pushbroom imaging principle, the image motion at the edge of the foreground image of the linear object is extracted using image processing technology including image segment and edge detection methods. Then the image motion is analyzed in the time and frequency domains. The proposed method has been successfully demonstrated for the angular vibration measurement by a flight test. The results of the vibration sensors and the position and orientation system of the flight tests are also given to validate the effectiveness and accuracy of the proposed approach.

基于激光自混调频特性的振动测量方法

基于激光自混调频特性的振动测量方法

Subspace Dimension Reduction for Faster Multiple Signal Classification in Blade Tip Timing

Blade tip timing (BTT) is a noncontacting vibration measurement method for rotating blade condition monitoring. The BTT sampling frequency is proportional to the number of probes under uniform probe layout and constant rotating speed. However, the limitation of the probe installation space in aeroengines causes the lack of probes, which leads to the inherent undersampled feature of the BTT signal. Thus, frequency identification of nonuniform undersampled signal has become a popular field in BTT signal processing. Multiple signal classification (MUSIC) is an array signal processing method that has been applied to this field. Nevertheless, the frequency traversal in MUSIC is a time-consuming process that will affect the online monitoring performance. Its running time is highly related to the dimension of the noise subspace. The subspace dimension reduced MUSIC (SDR-MUSIC) is proposed in this article to reduce the running time of MUSIC by reducing the dimension of noise subspace. Simulations and experiments are conducted to testify that SDR-MUSIC can significantly reduce the running time of MUSIC while ensuring accuracy.

Research on SS-OCT Vibration Measurement Method Based on Ultra-Small GRIN Fiber Probe

Research on SS-OCT Vibration Measurement Method Based on Ultra-Small GRIN Fiber Probe

Low-Frequency Vibration Measurement Based on the Concentric-Circle Grating Projection System

In low-frequency vibration measurement field, optical dynamic 3-D measurement based on camera-projector system is a novel approach. In this system, linear sinusoidal grating is the most common projection mode, which can meet the requirements of some vibration measurement. However, the dynamic measurement range of amplitude using the combination of linear grating and Fourier transform profilometry (FTP) is limited in some vibration measurement environments, because the linear fringe is periodic. To solve the problem, this article proposes a low-frequency vibration measurement method based on the concentric-circle grating camera-projector system and FTP. The center of the circle is traced dynamically and the coordinate system is transformed with the center of the circle as the origin. The phase distribution of concentric-circle grating is obtained by coordinate system transformation and FTP. By exploring the relationship between phase and relative height, the time-varying curve of the object surface height is recovered, which contains the vibration information. The experiments compare the measurement ability of the concentric-circle and linear grating. The results show that the linear grating and concentric-circle grating with the similar amplitude resolution have different amplitude measurement range. In this experiment, the maximum measurement range of linear grating is about 2.4 mm, while that of concentric-circle grating is more than about 3.9 mm. It means that the concentric-circle grating projection method can measure a large dynamic range of amplitude under the condition that the center of the circle can be traced, and solve the problem of amplitude limitation of linear grating in the use of FTP.