Vibration Measurement Method Research Articles

Laser dot projection videogrammetry for vibration measurement and control of a piezoelectric flexible cantilever plate

A novel full-field non-contact vibration measurement method is investigated for a piezoelectric flexible cantilever plate, using laser dot-projection videogrammetry. Several laser dots are projected as marks for visual system. The three-dimensional coordinates of each mark are monitored by a binocular stereo vision system, composed of two cameras. After image processing, the vibration signal of the first bending mode is obtained. For the first torsional mode, two laser displacement sensors are utilized to detect the vibration. To suppress the residual vibration quickly, an adaptive nonlinear controller and a fuzzy tuning nonlinear controller are designed and adopted. To verify the investigated measurement and control methods, experiments are conducted by using a piezoelectric flexible cantilever plate experimental platform. The experimental results demonstrate that the investigated laser dot projection measurement method is effective for first bending vibration detection. Furthermore, compared with PD control, the adopted nonlinear algorithms have better damping performance, especially for small amplitude residual vibration.

A feasible vibration measurement and active control method of reinforced concrete lightweight pier railway bridges for heavy-haul monorail trains

This paper aims at introducing a novel method to control the lateral vibration of reinforced concrete, lightweight pier railway bridges (LPRBs) with heavy-haul (HH) monorail trains. For this purpose, a two-pier LPRB was strengthened using different techniques, and the dynamic performance of the reinforced bridge was evaluated for all the configurations. This paper compared the dynamic performance of LPRB increased by different plans. Meanwhile, a HH monorail train with two bogies was described by a three-dimension (3D) discrete rigid multi-body system with 23 degrees of freedoms (DOFs), while the two-pier LPRB was considered as an assemblage of beam elements with six DOFs at each node. Then, a finite element (FE) model train-bridge coupling system (TBCS) was set up based on the time-varying theory. After massive experimentally and numerically study, the dynamic analyses of the bridge and the running safety (RS) indexes of the train were conducted for each reinforcement plan using the program Dynamic Interaction Analysis for HH Train-Bridge System (DIAHHTBS). The results show that both the dynamic responses of the bridge and RS indices of the trains fulfilled the requirements in relevant specifications. It might mean that the proposed reinforcement method can strengthen the lateral stiffness of the bridge and reduce the amplitude of lateral vibration.

New step to improve the accuracy of blade tip timing method without once per revolution

Abstract The mechanical vibration has always been one of the main factors that restrict the improvement of turbomachinery performance such as aero-engines. Blade vibration is one of the most important obstacle. As a non-intrusive vibration measurement method, blade tip timing (BTT) technology has the potential to replace strain gauges for blade dynamic stress monitoring. However, it still faces enormous challenges, one of which is the accuracy and reliability of the once per revolution (OPR) probe. Here, an efficient and high-precision compound reference (CR) based BTT method without OPR is proposed. The method is based on straight line fitting (SLF), and taking the blade at the midpoint of the SLF interval as the reference blade. The vibration displacement of the reference blade is obtained by the SLF of the time of arrival (ToA) of probe No. 1. Further, taking the blade as the reference, the vibration displacement of other blades is obtained. With this method, the actual blade installation angle and the probe installation angle can be measured simultaneously based on the none OPR method so as to further improving the measurement accuracy. By the numerical simulation, high speed test-rig and large scale industry turbo fan verification, the results indicate that the method has the merit of stronger anti-noise ability, less uncertainty, and much higher computational efficiency. Whereby, high-efficiency blade vibration measurement can be achieved in the whole operating speed range.

Vibration Measurement Method for Artificial Structure Based on MIMO Imaging Radar

Measuring the vibrating states of an artificial structure is an important approach to monitor the stability of the structure. However, the existing radar vibration measurement methods do not have enough azimuth resolution for measuring the vibrations in a relatively large scene, which contains multiple buildings or a large building. For such application scene, this paper proposes a vibration measurement method based on multiple-input multiple-output imaging radar system, which can achieve high azimuth resolution. Features of the proposed method are threefold: first of all, by utilizing the ability of quickly acquiring imaging data, the proposed method can achieve vibration measurement for the entire area simultaneously; second, in order to detect the positions of vibrating objects and decrease the time of vibration parameter estimation part, this paper proposes vibration similarity index to quantify the similarity between the detected signal and ideal vibration signal; at last, due to the limitations of the hardware performance, this paper adopts multiple signal classification least-squares estimation method to estimate the vibrating frequency and amplitude. To evaluate the performance of the proposed method, ideal point target simulation and vibrating calibrator experiment have been conducted, and the results show that the positions and the vibrating parameters of the vibrating objects fit well with the reference values. In addition, car experiment and bridge experiment have been carried out to verify the ability of the proposed method to measure the vibration of real artificial structures, which cannot be seen as point targets.

The diagnostic method of rolling bearing in planetary gearbox operating at variable load

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Asphalt road surface vibration and force distribution generated by pickup truck braking

This paper presents a method for dynamic vibration and force measurement using a microcontroller. In the experiment, data were obtained by vibration frequency measurement at the asphalt road surface when the vehicle brakes were applied, and the data were analyzed using additional equipment and software. By using the SW-420 device, frequencies in the range of 10–1000 Hz were applied and tested. The results obtained indicated that the proposed system can be used to determine the force acting on the road surface while the vehicle is in motion. The estimated forces were within the range of 0.20–4.10 × 1010 N at velocities of 20–100 km·h−1. A relative maximum error of 0.20% was achieved.

Frequency domain triangulation for full-field 3D operating-deflection-shape identification

Abstract The use of high-speed camera systems in vibration measurements is typically limited to identifying motion, transversal to the optical axis, due to an inherent limitation of 2D imaging systems. Depth information, lost in the imaging process, can be recovered by using the well-established 3D DIC technique, but is still limited to a single face of the object, observed by the stereo pair. In this research a full-field 3D operating-deflection-shape measurement technique, based on frequency-domain triangulation of image-data, is presented. A mathematical model of frequency-domain perspective transformation of small harmonic motion is introduced. This model is used to relate multiview image data to spatial amplitude spectra of the observed displacement. Using the developed method, spatial small harmonic motion of arbitrary-shaped specimen can be identified in the frequency domain using only a single, moving high-speed camera, extending the field-of-view of the established image-based vibration measurement methods.

Trajectory planning and diagonal recurrent neural network vibration control of a flexible manipulator using structural light sensor

Abstract A new vibration measurement method and active control algorithm for a flexible manipulator are investigated. A non-contact vibration measurement method based on structural light sensor is proposed. During and after the point-to-point motion, the locally controlled autoregressive moving average (CARMA) model of the flexible manipulator is determined through experiments. Based on the model, the particle swarm optimization (PSO) algorithm is adopted to obtain the optimal vibration suppression trajectory. Moreover, considering the time-varying and nonlinear characteristics of the flexible manipulator, a diagonal recurrent neural network (DRNN) control algorithm is designed to suppress residual vibration, which consists of an on-line identifier and a vibration control signal generator. The experiment setup is constructed. Compared with trapezoidal trajectory and classic smooth trajectories, planning an optimal trajectory can cause less vibration under the same motion requirements. Experimental results demonstrated that the DRNN controller is superior to the classical PD controller on vibration suppression, especially for the small amplitude residual vibration. Furthermore, the hybrid control strategy of optimal trajectory planning and DRNN control has the advantages of ensuring smoother motion and faster residual vibration suppression speed.

회전수 측정 센서를 이용한 진동 계측 기법 연구

When conducting rotary test in wind tunnel, measuring rotational speed and vibration is important to protect the facility and the model. However, it is difficult to install the additional vibration sensor inside the test model since the space is narrow. In order to overcome this problem, this paper proposes noncontact method of vibration measurement without using additional vibration sensors in rotary wind tunnel testing. The proposed method exploits the noncontact rotational speed measurement system and uses the output signal of this system for measuring vibration displacement. The test results confirm that the proposed method can measure the vibration displacement of rotating machine properly.

Target-free vision-based technique for vibration measurements of structures subjected to out-of-plane movements

Vibration measurements have been widely used for structural health monitoring (SHM). Usually, wired sensors are required to attach on the testing structure, which may be arduous, costly and sometimes impossible to install those sensors on the remote and inaccessible part of the structure to be monitored. To overcome the limitations of contact sensors based vibration measurement methods, computer vision and digital image processing based methods have been proposed recently to measure the dynamic displacement of structures. Real-life structure subjected to bi-directional dynamic forces is susceptible to significant out-of-plane movement. Measuring the vibrations of structures under the out-of-plane movements using target-free vision-based methods have not been well studied. This paper proposes a target-free vision-based approach to obtain the vibration displacement and acceleration of structures subjected to out-of-plane movements from minor level excitations. The proposed approach consists of the selection of a region of interest (ROI), key-feature detection and feature extraction, tracking and matching of the features along the entire video, while there is no artificial target attached on the structure. The accuracy of the proposed approach is verified by conducting a number of experimental tests on a reinforced concrete structural column subjected to bi-directional ground motions with peak ground accelerations (PGA) ranging from 0.01 g to 1.0 g. The results obtained by the proposed approach are compared with those measured by using the conventional accelerometer and laser displacement sensor (LDS). It is found that the proposed approach accurately measures the displacement and acceleration time histories of the tested structure. Modal identification is conducted using the measured vibration responses, and natural frequencies can be identified accurately. The results demonstrate that the proposed approach is reliable and accurate to measure the dynamic responses and perform the system modal identification for structural health monitoring.

Design of wireless vibration measuring system for material processing machinery equipment

Aiming at the problem of mechanical vibration measurement in material processing equipment at present, a vibration measurement method using MEMS micro-accelerometer as measuring sensor is proposed. The wireless sensor module with the core of CC2430 device is used to form the sending and receiving node of the signal. ADS8344 chip is used as the data acquisition converter to collect the vibration signals output by MEMS sensor. Collection, storage, control and other functional modules are integrated in the single chip microcomputer. At last, the vibration peak value and frequency of the system are tested, and the feasibility of the system is verified.

Broad Range and High Precision Self-Mixing Interferometer Based on Spectral Analysis With Multiple Reflections

In this paper, a novel self-mixing interferometer is proposed with spectral analysis by multiple reflection technique. The relationship between the vibration amplitude, the dominant frequency, and the reflection time is deduced, which indicates that the theoretical minimum measurable vibration amplitude is 0.21λ/G(N,θ) and the precision is about 0.08λ/G(N,θ). The displacement sensitivity gain G(N,θ) increases with the reflection time. Theoretical analysis results show that the proposed method for vibration measurement has the advantages of high precision and broad measurement range, especially for the measurement of amplitude much smaller than λ/2. The validity of the method is tested by several experiments with different amplitudes and reflection times. An amplitude of 75 nm has been proved to be measurable and the absolute error is 5.43 nm, which is within the theoretical error range. The proposed method plays an important role in high precision and nanoscale measurement.

Evaluation Method for Vibration Measurement on Casing in Aeroengine: Theoretical Analysis and Experimental Study

The vibration measurement location is the basis for effective monitoring of aeroengine vibration conditions. Measurement locations need to reflect the vibration of the rotor sufficiently, while complex structures of the aeroengine bring many excitation sources. This paper presents an evaluation methodology for vibration measurement on casing in the aeroengine. A number of indexes are defined to quantify and characterize the vibration measurement ability of main measurement locations on casing for rotor vibration. A dynamic model of a dual‐rotor‐casing system is established according to the support structure of a certain type of aeroengine. By means of the introduced evaluation method, the vibration relation between rotors and the main vibration measurement sections is analyzed. Response characteristics and performance orders of measurement sections are given. The rationality of theoretical results is sound verified by experiments on a designed pneumatic‐driven double‐rotor‐casing test bench. The best measured vibration section is consistent with the actual on‐board vibration section of the engine, which further demonstrates the effectiveness of the evaluation method. The research results can provide a basis for the selection and optimization of vibration measurement locations and fault diagnosis in the aeroengine. Furthermore, the application of this method is not limited to aeroengine vibration analysis and sensor measurement location optimization, but will be useful for vibration analysis of other rotating machinery.

Pixel-wise Amplitude Distribution Evaluation in Time Average Digital Holography

This article introduces a new holographic method for harmonic vibration measurement. The method called time average sweeping digital holography (TASDH) is based on the continuous shift of fringe pattern described by Bessel function over the object surface. The shift is done by phase modulation in one arm of holographic interferometer. Such temporal phase sweeping allows for evaluation of the vibration amplitude value independently in each pixel by application of intensity values cross-correlation of steady state and oscillating object. Main advantage of proposed technique with respect to other methods of digital holographic vibration is its ability to measure the amplitude of vibration without the risk of interference order mismatch. Thanks to above mentioned properties, the method allows measurement of amplitude modes with high slopes or discontinuous surfaces as well as partially shaded objects. The method was experimentally tested by measuring the bending beam cantilever. The standard deviation of the measured noise is below nanometer.

A computer vision-based vibration measurement method for wind tunnel tests of high-rise buildings

This paper presents a computer vision-based vibration measurement (VVM) method for wind tunnel tests of typical aeroelastic high-rise building models. After reviewing the existing vision-based measurement techniques, an advanced object-tracking algorithm, so called the template-corner algorithm, is developed to achieve more accurate vibration measurements in wind tunnel setups. Based on the newly developed object-tracking algorithm, the proposed VVM method can measure wind-induced dynamic displacements and acceleration responses, as well as identify dynamic model characteristics. The method is cost effective and can acquire all horizontal responses at the top plane of the building model under various wind angle conditions using only one complementary metal-oxide-semiconductor (CMOS) camera, with significant flexibility and adequate resolutions. A free vibration test and a series of wind tunnel tests for a typical aeroelastic high-rise building model were conducted to validate the proposed vision-based method. The results obtained from the proposed method were carefully compared with those from conventional measurement techniques using a laser displacement sensor and an accelerometer. The comparison results confirm the accuracy and feasibility of the VVM method for obtaining wind-induced dynamic responses of aeroelastic tall building models.

Vibration measurement method based on point tracking for irregular structures

A novel vibration measurement method through binocular photogrammetry is proposed to solve the problem of vibration sensing for 3D structures with irregular surfaces. Radial and tangential distortions in the image modeling process are considered for camera calibration through nonlinear optimization with Levenberg-Marquardt algorithm. Precise positioning, tracking and matching techniques are analyzed and developed in image processing. As an example, a wind turbine blade’s vibration is photographed and calculated, and the measured vibration displacement is consistent with that of the hammer method. The result shows that the relative errors of the first and second order natural vibration frequencies are below 4%. The proposed photogrammetry method is simple, efficient, feasible and reliable, and can be applied to the field of dynamic testing of large irregular structures.

A Novel Low Frequency Vibration Measurement Method Based on Single Camera

In recent years, low frequency vibration measurement is being widely concerned in many applications, because low frequency vibration usually introduces a strong influence. The low frequency vibration is commonly measured by the laser interferometry, requiring a complicated system and a high cost laser interferometer, and its flexibility in field vibration measurement is poor; or the method using vibration transducer, requiring a transducer with known sensitivity, and its measurement precision is not high. In this paper, we propose a novel method based on single camera, which achieves low frequency vibration measurement via collecting and processing sufficient frame sequence images. The proposed method is compared with the heterodyne interferometry by measuring the vibration displacements of a long-stroke shaker simultaneously. Experimental results show the proposed method realizes <1% vibration displacement measurement precision at frequencies between 0.05 Hz-5 Hz.

A novel vibration measurement and active control method for a hinged flexible two-connected piezoelectric plate

Abstract A novel non-contact vibration measurement method using binocular vision sensors is proposed for piezoelectric flexible hinged plate. Decoupling methods of the bending and torsional low frequency vibration on measurement and driving control are investigated, using binocular vision sensors and piezoelectric actuators. A radial basis function neural network controller (RBFNNC) is designed to suppress both the larger and the smaller amplitude vibrations. To verify the non-contact measurement method and the designed controller, an experimental setup of the flexible hinged plate with binocular vision is constructed. Experiments on vibration measurement and control are conducted by using binocular vision sensors and the designed RBFNNC controllers, compared with the classical proportional and derivative (PD) control algorithm. The experimental measurement results demonstrate that the binocular vision sensors can detect the low-frequency bending and torsional vibration effectively. Furthermore, the designed RBF can suppress the bending vibration more quickly than the designed PD controller owing to the adjustment of the RBF control, especially for the small amplitude residual vibrations.

วิธีการตรวจวัดการสั่นสะเทือนแบบพลวัตของพื้นผิวถนนยางมะตอยด้วยข้อมูลจากไมโครคอนโทรลเลอร์

วิธีการตรวจวัดการสั่นสะเทือนแบบพลวัตของพื้นผิวถนนยางมะตอยด้วยข้อมูลจากไมโครคอนโทรลเลอร์

Analysis of the effect of V-shape and Rectangular Shape cracks on the natural frequencies of a spring steel cantilever beam

Crack is mostly found in the material which has less fatigue strength. It is progressive and limited to a small area structural damage that occurs when a material is subjected to cyclic loading. Since more than two decades, natural frequency used as an input for crack detection. In this study, the effects of multiple cracks on the dynamics of the structure are studied. The objective of this study is to see the effect of v shape and rectangular shape edge cracks on the natural frequency and static deflection on the spring steel cantilever beam. V shape and Rectangular shape crack exists in the turbines, pumps and other relevant applications in service. In the present study, free vibration analysis of a cracked cantilever beam is performed in order to see the effect of V shape and rectangular shape cracks on the natural frequency. Through the detailed study it is found that all the v shape cracked cases gives natural frequency comparatively on higher side. The variations in the natural frequency of v shape cracked cases is less than rectangular shape cracked cases with respect to natural frequency of undamaged beam. Consequently, the presence of small size rectangular shape crack in the beam can be effectively detected by vibration measurement methods than small size v shape crack. At the last location, when crack depth increases, value of natural frequency remains least affected. From static analysis found static deflection is largest for the case which has least natural frequency.