Monitoring and maintaining the health of wind turbine blades has long been one of the challenges facing the global wind energy industry. Detecting damage to a wind turbine blade is important for ...planning blade repair, avoiding aggravated blade damage, and extending the sustainability of blade operation. This paper firstly introduces the existing wind turbine blade detection methods and reviews the research progress and trends of monitoring of wind turbine composite blades based on acoustic signals. Compared with other blade damage detection technologies, acoustic emission (AE) signal detection technology has the advantage of time lead. It presents the potential to detect leaf damage by detecting the presence of cracks and growth failures and can also be used to determine the location of leaf damage sources. The detection technology based on the blade aerodynamic noise signal has the potential of blade damage detection, as well as the advantages of convenient sensor installation and real-time and remote signal acquisition. Therefore, this paper focuses on the review and analysis of wind power blade structural integrity detection and damage source location technology based on acoustic signals, as well as the automatic detection and classification method of wind power blade failure mechanisms combined with machine learning algorithm. In addition to providing a reference for understanding wind power health detection methods based on AE signals and aerodynamic noise signals, this paper also points out the development trend and prospects of blade damage detection technology. It has important reference value for the practical application of non-destructive, remote, and real-time monitoring of wind power blades.
With the increasing precision, complexity, and diversification of CNC machine tools, the requirements for fault detection technology of CNC machine tools are getting essential.If problems such as ...tool wear and spindle locking can not be found in time, it will lead to the waste of a large number of raw materials and production time. Aiming at the fault problem of high-precision NC machine tools, this paper uses the method based on DWT and statistical domain to extract features from audio signals to form data sets, and proposes a lightweight convolution neural network to identify the fault types of machine tools.Firstly, features are extracted from MIMII public data sets, and evaluates the data sets by using three machine learning models (SVM, KNN, and GNB).The results show that when facing different materials and structures, the model trained by extracting features from mechanical audio signals based on wavelet transform and statistical domain has good prediction accuracy.Then, this method is used for audio data of CNC machine tools in a real factory environment.The data set includes six common machine tool faults, including normal operation, tool wear, spindle locking, tool idling, abnormal impact, and back cutting amount.A lightweight convolution neural network was used to identify fault types in machine tools.The experimental results show that the recognition accuracy of the trained model is 97.85%, AUC is 0.9984, and F1 is 0.9769. Compared with the DNN proposed by Jong-Yi (Kuo et al., 2022) 1 , it has been improved in all aspects. The accuracy of fault recognition is improved from 96.1% to 97.85% compared with the method of sound fusion feature and OCSVM (Ding et al., 2022) 2.
•This paper investigates a new method to identify mechanical failure problems by audio parameters.•The combination of DWT features extraction and improved CNN is used to detect the machine status.•By extracting the statistical domain information of the audio time domain, the Mel plot is replaced as the input for training.•A lightweight convolutional neural network with three channels with added filters.
In this paper, the radiation characteristics and active structural acoustic control of a submerged cylindrical shell at low frequencies are investigated. First, the coupled vibro-acoustic equations ...for a submerged finite cylindrical shell are solved by a modal decomposition method, and the radiation impedance is obtained by the fast Fourier transform. The modal shapes of the first ten acoustic radiation modes and the structure-dependent radiation modes are presented. The relationships between the vibration modes and the radiation modes as well as the contributions of the radiation modes to the radiated sound power are given at low frequencies. Finally, active structural acoustic control of a submerged finite cylindrical shell is investigated by considering the fluid-structure coupled interactions. The physical mechanism of the active control is discussed based on the relationship between the vibration and radiation modes. The results showed that, at low frequencies, only the first several radiation modes contributed to the sound power radiated from a submerged finite cylindrical shell excited by a radial point force. By determining the radiation modes that dominate the contribution to the radiated sound, the physical mechanism of the active control is explained, providing a potential tool to allow active control of the vibro-acoustic responses of submerged structures more effectively.
Medium-and-long-term load forecasting plays an important role in energy policy implementation and electric department investment decision. Aiming to improve the robustness and accuracy of annual ...electric load forecasting, a robust weighted combination load forecasting method based on forecast model filtering and adaptive variable weight determination is proposed. Similar years of selection is carried out based on the similarity between the history year and the forecast year. The forecast models are filtered to select the better ones according to their comprehensive validity degrees. To determine the adaptive variable weight of the selected forecast models, the disturbance variable is introduced into Immune Algorithm-Particle Swarm Optimization (IA-PSO) and the adaptive adjustable strategy of particle search speed is established. Based on the forecast model weight determined by improved IA-PSO, the weighted combination forecast of annual electric load is obtained. The given case study illustrates the correctness and feasibility of the proposed method.
•The transfer impedance matrix is calculated by numerical approach.•There exist four equivalent energy transmission paths.•The transmission paths all have the band-pass characteristics.•The sound ...energy transmission in each pass-band is suppressed after control.
This paper presents an active triple-panel sound insulation structure with an idealized controllable point force acting on the middle plate. A novel analytical approach based on sound energy transmission rule is proposed to achieve the physical mechanism study. The transfer impedance matrix of the incident and middle plate is calculated using numerical approach. And the rule of sound energy transmission through the triple-panel structure is concluded by indirectly analyzing the radiated sound power of the three plates. Finally the physical mechanism of noise insulation is investigated from the point of view of the change in behaviors of energy transmission in controlled and uncontrolled conditions. Results obtained demonstrate that there exist four different energy transmission paths for four panel mode groups. The energy transmission is independent in each path and they are all of band-pass characteristic. The role of the middle plate and two cavities is very similar to the band-pass filter whose pass-band is different for different mode groups. The essence of active noise insulation lies in the fact that the energy transmission in each path is suppressed in its pass-band after control. This greatly improves sound insulation capability of the triple-panel structure and leads to sound propagation being blocked.
This paper presents a theoretical investigation on actively controlling the low frequency sound absorption of large-sized micro-perforated panel absorber (MPPA) by using point source placed in the ...cavity. The large sized active MPPA is an easily implemented and cost-effective scheme for achieving superior low frequency sound absorption in large area. The modal analysis approach is used to establish the theoretical model of such active MPPA. The physical mechanism of active control is analyzed and some physical insights are summarized. Based on these conclusions, the error sensing strategy of the large sized active MPPA is also constructed. Finally, experimental tests are carried out to validate the theoretical modeling and findings. Results show that the sound absorption performance can be significantly improved after control in a wide low frequency range below the cutoff frequency. The optimal position of the point source is at the central of the cavity section, in which case the cutoff frequency is the largest and depends on the length of the short side of the active MPPA. The control mechanism of sound absorption improvement is to enhance the Helmholtz type resonant absorption by suppressing the cavity sound field. The high order cavity mode (except for (0,0,0) mode) has no contribution to sound absorption improvement due to the symmetrical property of their mode shape. The pressure release (PR) and impedance matching (IM) strategies are still applicable for the large sized active MPPA. Relative small sized cavity or low frequency excitation can guarantee the uniformity of the cavity sound field after control, which is conducive to achieve remarkable improvement of sound absorption.
This paper presents an analytical investigation on physical mechanisms of actively controlling sound transmission through a rib stiffened double-panel structure using point source in the cavity. The ...combined modal expansion and vibro-acoustic coupling methods are applied to establish the theoretical model of such active structure. Under the condition of minimizing radiated power of the radiating ribbed plate, the physical mechanisms are interpreted in detail from the point of view of modal couplings similar as that used in existed literatures. Results obtained demonstrate that the rule of sound energy transmission and the physical mechanisms for the rib stiffened double-panel structure are all changed, and affected by the coupling effects of the rib when compared with the analytical results obtained for unribbed double-panel case. By taking the coupling effects of the rib into considerations, the cavity modal suppression and rearrangement mechanisms obtained in existed investigations are modified and supplemented for the ribbed plate case, which gives a clear interpretation for the physical nature involved in the active rib stiffened double-panel structure.
Injection behaviors of printheads are concerned by engineers since they affect the whole working performances and the printing quality of 3D printing device. In view of the quality instability issue ...for sand molds caused by the fluctuation of the droplet injection performance, a study on the relationship of the driving waveform parameters with the droplet injection performance of a casting sand mold printhead and the printing quality of the sand mold was carried out. Comprehensively considering the applied background of 3D printing in casting sand molds and using the separation of variables method, the quantitative relationship between the driving waveform parameters and the droplet injection characteristics was set up, and the injection performance of the printhead under the current waveform was evaluated through experiments. This article puts forward an optimal waveform for use in casting sand printing. Based on the analysis of existing conclusions, by using special equipment for casting sand mold 3D printing, the printing quality of the sand mold under the new waveform and the current waveform was studied via a comparison experiment. The results show that the new waveform is more suitable for sand mold printing of high-viscosity fluid, as it avoids the presence of satellite droplets. The qualification rate in terms of the sand mold size is enhanced by 44%, and the mechanical properties of the sand mold are effectively improved. This study provides a reliable basis for ensuring dimensional accuracy in the application of 3D printing technology in the precision casting field.
•The ribbed plat modes are the superposition of several base plate modes.•The modal suppression and rearrangement mechanisms are modified and renewed.•Due to the coupling effects of the rib, some new ...rules of active control are found.
An analytical study of mechanisms of active control of sound radiation from a rib stiffened plate is presented in this letter. Using the well-known modal expansion method to solve the beam/plate coupling vibration response, the physical mechanisms are interpreted in an analytical way similar as that used in the unribbed plate case. But some special rules are discovered for the ribbed plate case. The primary characteristic for the ribbed plate is that its new resonant modes are essentially the superposition of a couple of specific base plate modes that possess the same vibration pattern along the rib. These modes should be all suppressed in controlled condition to achieve on-resonances noise reduction. A large number of base plate modes contribute to off-resonances sound radiation such that multi-point forces are needed to rearrange their amplitudes and phases to guarantee their sound radiation being canceled each other. The imperfect control effects when control force acting on nodal areas of the mode of the ribbed plate are due to the opposite vibration states of the corresponding base plate modes where the control force applied for suppressing one mode may consequentially excite another.
Purpose
This study aims to investigate the vibration effects on ball grid array lifetime.
Design/methodology/approach
Several finite element method simulations and experiments were performed.
...Findings
An optimized circuit configuration was found.
Originality/value
The originality of paper is confirmed by authors.
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