- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
On the Application of Laser Vibrometry to Perform Structural Health Monitoring in Non-Stationary Conditions of a Hydropower Dam
摘要： This paper presents the ?rst application of the Laser Doppler Vibrometer (LDV) in non-stationary conditions within a hydropower plant powerhouse. The aim of this research is to develop a methodology to include non-contact vibration monitoring as part of structural health monitoring of concrete dams. We have performed in-situ structural vibration measurements on the run-of-the-river Bre?ice dam in Slovenia during the start-up tests and regular operation. In recent decades, the rapid development of laser measurement technology has provided powerful methods for a variety of measuring tasks. Despite these recent developments, the use of lasers for measuring has been limited to sites provided with stationary conditions. This paper explains the elimination of pseudo-vibration and measurement noise inherent in the non-stationary conditions of the site. Upon removal of the noise, fatigue of the different structural elements of the powerhouse could be identi?ed if signi?cant changes over time are observed in the eigenfrequencies. The use of laser technology is to complement the regular monitoring activities on large dams, since observation and analysis of integrity parameters provide indispensable information for decision making and maintaining good structural health of ageing dams.
关键词： concrete dam,dam monitoring,laser doppler vibrometry,vibration,accelerometers
更新于2025-09-11 14:15:04
-
Analysis on the Influence of the Distributed Photovoltaic on the Line Loss of Distribution System
摘要： In order to analyze synchronization control problems of two non-identical homodromy eccentric rotors (ERs) in a nonlinearly coupled system of vibrating machinery-part (NCS-VMP), a new electromechanical coupling nonlinear dynamic model considering nonlinear acting force of the part and nonlinear support is established, NCS- VMP’s complex control is converted into rotating speed and phase synchronous control of two homodromy non- identical exciters. By considering the dynamic interactions among the vibration body, the part and the ERs, the nonlinear dynamical equation of the NCS-VMP are established. An accurate synchronization control of speed and phase method are proposed for two homodromy ERs in NCS-VMP. The precise speed and phase synchronization control is mainly re?ected as: The cross-coupling control strategy is used which considering the coupling effect between two co-rotating exciters. The radial basis function network adaptive global sliding mode algorithm (RBFN- AGSMA) is used to adaptively approximate the total uncertainty of system including the nonlinear support and the nonlinear force of the parts, which can effectively reduce the estimation error. The radial basis function network method can suppress the jitter of the system and make the in?uence of the system more stable after replacing the sign function. The stability of RBFN-AGSMA controller is proved by Lyapunov theory. The controller’s property is veri?ed through numerical methods and taking the sliding mode control (SMC) algorithm into comparison. Results indicate that the designed control method can reduce chattering clearly compared with the SMC algorithm, and it is capable to improve the control accuracy of two non-identical homodromy exciters. By studying the effects of parameter change in the NCS-VMP on the system, the strong robustness of RBF network global sliding mode controller to parameter perturbations is proved. It is proposed that RBFN-AGSMA controller can control two nonidentical homodromy ERs in NCS-VMP to achieve accurate vibration trajectory in the working direction.
关键词： RBF network adaptive global sliding mode algorithm,stability,nonidentical homodromy coupling exciters,Nonlinearity support,nonlinear coupled vibration system
更新于2025-09-11 14:15:04
-
A Combined Events Recognition Scheme Using Hybrid Features in Distributed Optical Fiber Vibration Sensing System
摘要： In this paper, a high efficiency multiple events recognition scheme based on a hybrid feature extraction algorithm and a combined classifier for distributed optical fiber vibration sensing (DOFVS) system has been proposed and demonstrated. The hybrid feature vectors are extracted by using zero crossing rate, sample entropy, wavelet packet energy entropy, kurtosis, and multiscale permutation entropy. A combined classifier of support vector machine and radial basis function neural network is proposed to improve the reliability of the recognition results. The recognition result is given only when both of the two classifiers output same event types. The experimental results demonstrated that the average identification rate of five typical patterns (no intrusion, waggling the fence, climbing the fence, kicking the fence, and cutting the fence) over 97% is achieved through the combined classifier. Moreover, the whole recognition processing speed of the combined scheme is also good of real time performance, which can be limited in 1.1 s. Therefore, this kind of events recognition scheme has a quite promising application prospects in DOFVS system.
关键词： hybrid feature vectors,signal analysis,Distributed vibration sensing,events recognition,optical fiber,combined classifier
更新于2025-09-11 14:15:04
-
Polarimetric Fiber Vibration Sensor Based on Polarization-Diversified Loop Using Short Polarization-Maintaining Photonic Crystal Fiber
摘要： In this paper, we demonstrated a polarimetric fiber vibration sensor based on a polarization-diversified loop (PDL) with short polarization-maintaining photonic crystal fiber (PM-PCF) as a sensor head and investigated the dependence of its frequency response on the sensing fiber length. The fabricated PM-PCF vibration sensor is composed of a polarization beam splitter for forming the PDL, PM-PCF as a sensor head, and two wave plates such as a quarter-wave plate and a half-wave plate. A laser diode and a photodetector were also utilized for intensity-based vibration measurement. In particular, two kinds of PM-PCF segments with fiber lengths of ～6 and ～10 cm were employed to explore the effect of the sensor head length on the sensor frequency response. The frequency response was examined over 1–3000 Hz using a piezoelectric transducer that can apply single-frequency vibration to the sensor head. Every measured frequency response showed a resonance peak at each sensor head length, and cut-off frequencies were measured as ～1240 and ～794 Hz for PM-PCF lengths of ～6 and ～10 cm, respectively. That is, a higher cut-off frequency was obtained in a shorter sensor head length. Moreover, it was observed that the sensor head length dependence of the frequency response was maximized in a frequency range from 1000 to 2400 Hz and faded away beyond 2400 Hz. From the measurement results, it is concluded that the short sensor head can provide higher normalized sensitivity, i.e., better signal to noise ratio, at frequencies higher than the resonance frequency, let alone convenience of installation and in sensitiveness to external perturbations in a PDL-based PM-PCF vibration sensor. The phase shift per unit strain and the minimum detectable strain perturbation, regarded as sensitivity and resolution, were measured as ～0.377 mrad/με and ～0.16 nε/Hz1/2 at 2000 Hz for ～6-cm-long PM-PCF, respectively.
关键词： Polarization-Maintaining Photonic Crystal Fiber,Polarization-Diversified Loop,Frequency Response,Optical Fiber Vibration Sensor
更新于2025-09-11 14:15:04
-
[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Monitoring Bridges Vibration Using a Ground Based Radar
摘要： Monitoring the stability of bridges under heavy traffic conditions is of paramount importance. Surveyors are interested in quantifying the amount of short-term vertical displacement due to traffic loads. A common way to measure the vertical oscillation of a bridge is by deploying reflectors/prisms on the bridge and using a total station. Alternatively lasers can be used to measure vibrations, but these are generally expensive. In this work, we are testing the use of relatively inexpensive technology based on a Stepped Frequency Continuous Waveform radar. We have acquired radar backscattering under bridges in Milton Keynes, UK and validated the results using a video camera synchronised with the radar acquisitions. Every time a truck was crossing the bridge an oscillation of around a millimetre was observed. Different trucks provided slightly different oscillations.
关键词： interferometry,buildings,vibration,stepped frequency continuous waveform,radar
更新于2025-09-10 09:29:36
-
Free Vibration Analysis of Variable Cross-Section Single-Layered Graphene Nano-Ribbons (SLGNRs) Using Differential Quadrature Method
摘要： In this article, free vibration of the variable cross-section (non-uniform) single-layered graphene nano-ribbons (SLGNRs) is investigated by using the Differential Quadrature Method (DQM). Here width of the cross-section is assumed to vary exponentially along the length of the nano-ribbon. Euler–Bernoulli beam theory is considered in conjunction with the nonlocal elasticity theory of Eringen. Step by step procedure is included and MATLAB code has been developed to obtain the numerical results for different scaling parameters as well as for four types of boundary conditions. Convergence study is carried out to illustrate the efficiency of the method and obtained results are validated with known results in special cases showing good agreement. Further, numerical as well as graphical results are depicted to show the effects of the nonuniform parameter, nonlocal parameter, aspect ratio and edge conditions on the frequency parameters.
关键词： SLGNR,vibration,DQM,euler-bernoulli beam theory,variable cross-section
更新于2025-09-10 09:29:36
-
A Kind of Vibration Sensor and Testing System in Electromechanical Equipment Based on Fiber Bragg Grating
摘要： Mechanical vibration analysis is an important index to measure the running state of the electromechanical equipment. The vibration signals contain the information about the equipment running state. This paper studies and designs the vibration monitoring system based on fiber Bragg grating (FBG). Through the finite element analysis simulation, optimizes the sensor's structure, and uses the labview software to compile the corresponding vibration monitoring analysis software. Finally verifies the detection effect of the monitoring system, through the pulse signal and continuous signal dynamic experimental analysis. The result of the experimental analysis shows: this vibration monitoring system can monitor the vibration information and analyze vibration state effectively. It has the advantages of reducing the temperature interference and lateral disturbance, and detects the vibration of three direction at the same time. So it is feasible to monitor the electromechanical equipment.
关键词： three-dimensional sensor,vibration monitoring analysis,electromechanical equipment,fiber Bragg grating
更新于2025-09-10 09:29:36
-
Buckling and free vibration analysis of piezoelectric laminated composite plates using various plate deformation theories
摘要： A finite strip method was developed for buckling and free vibration analysis of piezoelectric laminated composite plates based on various plate theories such as Zigzag, Refined plate and other higher order shear deformation theory by variation of transverse shear strains through plate thickness in the form of parabolic, sine and exponential. The plate edge conditions are considered to be simply supported and the polynomial shape functions are used to evaluate the in–plane and out–of–plane deflection and rotation of the normal cross section of plates in transverse direction. Numerical results were obtained based on various shear deformation plate theories to verify the proposed method. The effects of length to thickness ratio and fiber orientation of cross–ply and angle–ply laminate were presented. Also, the effect of different electrical conditions on the critical buckling load under in–plane forces and strains is investigated and electrical buckling load and natural frequency of piezoelectric laminate composite plates are calculated through numerical examples. In addition, the new results on the effect of piezoelectric layers thickness, placement of piezoelectric layers and also the effect of length to thickness ratio in the interaction of biaxial in–plane loading on critical buckling load were studied.
关键词： Piezoelectric Layers,Free Vibration,RPT,Buckling,Zigzag theory
更新于2025-09-10 09:29:36
-
[Ceramic Transactions Series] Ceramics for Environmental Systems (Ceramic Transactions, Volume 257) || Development of Microtextured Titanium Dioxide Surface by Using Microcutting Techniques
摘要： TiO2 possesses photocatalytic functions, even though they are relatively weak and required further enhancements for wider practical usages. On the other hand, improving materials surface functions by introducing surface textures is of great interest in various fields. This study aims to develop a high-functional photocatalytic surface by increasing the real surface area with the support of microcutting techniques. In this work, pure Ti plates, which was covered with numerous fine grooves fabricated by the microcutting and vibration-assisted microcutting techiniques, were anodized to obtain various regularly microtextured TiO2 film surfaces. Their wettabilties were examined to evaluate their photocatalitic potential. As a result, it is found that the wettability of the TiO2 film surfaces of regularly textured are superior to that of the mirror finished one under an ultraviolet rays irradiation environment.
关键词： anodic oxidation,microcutting,vibration-assisted microcutting,TiO2,wettability,photocatalytic
更新于2025-09-10 09:29:36
-
[ASME ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition - Oslo, Norway (Monday 11 June 2018)] Volume 7C: Structures and Dynamics - Optimal Placement and Sizing of Piezoelectric Material for Multiple-Mode Vibration Reduction
摘要： Modern turbomachinery blades have extremely low inherent damping, which can lead to high transient vibrations and failure through high-cycle fatigue. Recent research seeks methods to reduce vibration with minimal effect on the weight and aerodynamic efficiency of the blade. Smart materials present an interesting means to augment the mechanical characteristics of the blade while meeting the strict requirements of the turbomachinery environment. In particular, piezoelectric-based vibration reduction offers the potential to semi-actively reduce vibration while simultaneously harvesting enough energy to power the implementation. The placement and size of the piezoelectric material is critical to the vibration reduction capabilities of the system. Furthermore, the implementation should target multiple vibration modes. This work develops a procedure to optimize electromechanical coupling across multiple vibration modes for a representative turbine blade with a surface-mounted piezoelectric patch.
关键词： electromechanical coupling,piezoelectric material,turbomachinery blades,optimization,vibration reduction
更新于2025-09-09 09:28:46