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  • Articles  (263)
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  • Articles  (263)
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  • 1
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    Extraction method of weak underwater acoustic signal based on the combination of wavelet transform and empirical mode decomposition (2021)
    EDP Sciences
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    Publication Date: 2021-01-01
    Description: When studying underwater acoustic exploration, tracking and positioning, the target signals collected by hydrophones are often submerged in strong intermittent noise and environmental noise. In this paper, an algorithm that combines empirical mode decomposition and wavelet transform is proposed to achieve the efficient extraction of target signals in the environment with strong noise. First the calibration of baseline drift is performed on the algorithm, and then it is decomposed into different intrinsic mode functions via empirical mode. The wavelet threshold processing is conducted according to the correlation coefficient of each mode component and the original signal, and finally the signals are reconstructed. The simulation and experiment results show that compared with the conventional empirical mode decomposition method and wavelet threshold method, when the signal-to-noise ratio is low and there exist high-frequency intermittent jamming and baseline drift, the combined algorithm can better extract the target signal, laying the foundation for direction-of-arrival estimation and target positioning in the next step.
    Print ISSN: 2107-6839
    Electronic ISSN: 2107-6847
    Topics: Electrical Engineering, Measurement and Control Technology
    Published by EDP Sciences
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  • 2
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    Convolution and deconvolution: two mathematical tools to help performing tests in research and industry (2021)
    EDP Sciences
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    Publication Date: 2021-01-01
    Description: The concepts of convolution and deconvolution are well known in the field of physical measurement. In particular, they are of interest in the field of metrology, since they can positively influence the performance of the measurement. Numerous mathematical models and computer developments dedicated to convolution and deconvolution have emerged, enabling a more efficient use of experimental data; this in sectors as different as biology, astronomy, manufacturing and energy industries. The subject finds today a new topicality because it has been made accessible to a large public for applications such as processing photographic images. The purpose of this paper is to take into account some recent evolutions such as the introduction of convolution methods in international test standards. Thus, its first part delivers a few reminders of some associated definitions. They concern linear systems properties, and integral transforms. If convolution, in most cases, does not create major calculation problems, deconvolution on the contrary is an inverse problem, and as such needs more attention. The principles of some of the methods available today are exposed. In the third part, illustrations are given on recent examples of applications, belonging to the domain of electrical energy networks and photographic enhancement.
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    Topics: Electrical Engineering, Measurement and Control Technology
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  • 3
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    Research on fuzzy control charts for fuzzy multilevel quality characteristics (2021)
    EDP Sciences
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    Publication Date: 2021-01-01
    Description: Fuzzy control charts are proposed to solve the problem that traditional control charts cannot be applied to fuzzy quality characteristics. First, fuzzy quality characteristics are converted to representative statistics, which are fuzzy mode transformation, fuzzy level midrange transformation and fuzzy level median transformation. Control charts are designed based on the Poisson distribution. Second, the effects of the different statistics are analysed. Direct Fuzzy Control Charts are designed to avoid some information omission when translating fuzzy quality characteristics into representative statistics. The area ratio that falls within the control limits is used to conclude whether the process is relative out of control or in control. The performance of the control charts is analysed by MATLAB simulation. Finally, an example of an energy metre assembly is given to prove the proposed method.
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    Topics: Electrical Engineering, Measurement and Control Technology
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  • 4
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    Design and implementation of anulus-shaped ciliary structure for four-unit MEMS vector hydrophone (2021)
    EDP Sciences
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    Publication Date: 2021-01-01
    Description: Inspired from fish bionics, an anulus-shaped ciliary structure for four-unit MEMS vector hydrophone (AFUVH) is proposed in this paper. It replaces the previous bionic cilium-shaped structure and becomes a novel sensing structure in the four-unit MEMS vector hydrophone (FUVH), which realizes the complete simulation of the fish lateral line neuromasts structurally and functionally. It not only improves the sensitivity of FUVH, but also retains a sufficient bandwidth, which improves the overall performance of FUVH for monitoring remote ships noise. Meanwhile, this paper theoretically analyzes the performance of AFUVH for detecting acoustic signals. ANSYS 17.0 simulation is used to derive the parameters of effective structure and optimum dimension structure of annulus-shaped ciliary structure. Finally, the experimental results show that comparing with cilium-structured FUVH, the sensitivity of AFUVH with effective structure is increased by 3.92 dB, and the sensitivity of AFUVH with optimum dimension structure is increased by 5.87 dB, reaching up to −177.53 dB.
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    Topics: Electrical Engineering, Measurement and Control Technology
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  • 5
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    Characterization of NIS neutron irradiation facility for calibration and metrological application (2021)
    EDP Sciences
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    Publication Date: 2021-01-01
    Description: In this study, the Neutron Irradiation Facility (NIF) of the National Institute of Standards (NIS) was characterized for metrological applications to improve the accuracy of the calibration process. The NIS neutron irradiation facility consists of a 5 Ci Am-Be and 0.1 μg Cf-252 sources. The flux and dose rate of the Am-Be source was calculated by using MCNP5 code simulation at different distances from the source. The dose rate delivered by the source was determined using NM2-neutron monitor at different source-to-detector distances. A comparison between the measured and the calculated dose rate was performed and the deviation between them was explained in the skeletal arrangement of room scattering contribution. A shadow cone was designed and constructed to determine the scattering contribution at different source-to-detector distances. The optimum source-distance used for calibration was specified. It was found that the Am-Be calculated flux vary with distances from about 107–104 (n/cm2.S−1). The measured and the calculated dose rates were in agreement up to 150 cm distance from the source center after which the measured dose was greater than that calculated. The determined neutron scattering calculated from the measured-to-calculate dose ratio increased from 7% to 25% with increased distances from 150 to 300 cm. Moreover, the standard dose used in the calibration should be measured by a standard neutron monitor at each distance due to the higher value of the room scattering contribution where the optimum distance for calibration was 150 cm. The combined uncertainty of the measured neutron dose was 4.04%.
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    Topics: Electrical Engineering, Measurement and Control Technology
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  • 6
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    Evaluation of the measurement uncertainty of the stiffness modulus: test case of indirect tensile on cylindrical specimens (2021)
    EDP Sciences
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    Publication Date: 2021-01-01
    Description: This study treats the measurement uncertainties that we can find in the stiffness modulus of the bituminous test. We present all the sensors installed on rigidity modulus measurement chains and also their uncertainty ranges. Several parameters influence the rigidity module's value, such as the parameters related to experimental conditions, and others are rather connected to the equipment's specification, which are the speed, the loading level, the temperature, the tested sample dimension, and the data acquisition, etc. All these factors have a great influence on the value of the modulus of rigidity. To qualify the uncertainty factors, we used two approaches: the first one is made by following the method described by the GUM (Guide to the expression of uncertainty in measurement), the second approach based on the numerical simulation of the Monte Carlo. The two results are then compared for an interval of confidence of 95%. The paper also shows the employment of the basic methods of statistical analysis, such as the Comparing of two variances. Essential concepts in measurement uncertainty have been compiled and the determination of the stiffness module parameters are discussed. It has been demonstrated that the biggest source of error in the stiffness modulus measuring process is the repeatability has a contribution of around 45.23%.
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  • 7
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    Maintenance decision method considering inspection of mining equipment (2021)
    EDP Sciences
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    Publication Date: 2021-01-01
    Description: In coal mining industry, equipment safety and reliability during operation are essential in the production process. In recent years, along with the continuous improvement of intelligent coal mining equipment, reliable production requirements have simultaneously increased. Therefore, this article aims to study the maintenance decision making method that considers the safety inspection of a fully mechanized mining equipment group. The goal is to establish a maintenance decision making model that considers the safety overhaul of fully mechanized mining equipment group in order to minimize the total maintenance, production costs and safety risks. Firstly, the regular safety inspection procedure and the maintenance process were introduced. Then, a model guideline method that considers a fully mechanized mining equipment group's safety inspection was established. Finally, through the comparison of algorithms and maintenance strategies, it is proved that the maintenance decision optimization method proposed in this paper is of great significance for improving equipment reliability, improving comprehensive operation rate, reducing maintenance costs, and ensuring coal mine safety production.
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    Topics: Electrical Engineering, Measurement and Control Technology
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  • 8
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    Pointing error compensation of electro-optical detection systems using Gaussian process regression (2021)
    EDP Sciences
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    Publication Date: 2021-01-01
    Description: Pointing accuracy is an important indicator for electro-optical detection systems, as it significantly affects the system performance. However, as a result of misalignment, nonperpendicularity in the manufacturing and assembly processes, as well as the sensor errors such as camera distortion and angular sensor error, the pointing accuracy is significantly affected. These errors should be compensated before using the system. Parametric models are firstly proposed to compensate for the errors, whilst the semi-parametric models with the nonlinearity added are also put forward. Both methods should analyse the parametric part first, which is a complicated and inaccurate process. This paper presents a nonparametric model, without any prior information about mechanical dimensions, etc. It depends only on the test data. Gaussian Process regression is used to represent the relationship between data and predict the compensated output. The test results have shown that the regression variances have decreased by more than an order of magnitude, and the means have also been significantly reduced, with the pointing error well improved. The nonparametric model based on Gaussian Process is thus demonstrated to be an effective and powerful tool for the pointing error compensation.
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    Topics: Electrical Engineering, Measurement and Control Technology
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  • 9
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    Illuminance measurement by mobile devices with a diffuser dome: a comparative analysis of different platforms and applications (2021)
    EDP Sciences
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    Publication Date: 2021-01-01
    Description: Studies in the literature suggest that smartphone-based applications are not suitable for measuring illuminance levels. The measurement of this photometric quantity is useful in several sectors, including monitoring the adequacy of lighting conditions in workplaces. This work investigates the contribution of attaching a diffuser dome to the embedded light sensors of smartphones and tablets associated with different applications on their performance for measuring illuminance. Two experimental arrangements were developed using an LED lamp (294.84 lx, 475.58 lx, 880.39 lx) and a xenon arc lamp (607.94 lx, 1013.72 lx, 4012.26 lx, 23933.33 lx). In the comparative analysis, the impact of using diffusion dome attachment was evidenced, indicating its potential to enable some of the device/application combinations to achieve adequate performance for being applied in the daily assessment of illuminance.
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    Topics: Electrical Engineering, Measurement and Control Technology
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  • 10
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    Modeling and measurement of precision reducers' efficiency curve (2021)
    EDP Sciences
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    Publication Date: 2021-01-01
    Description: Transmission efficiency is the key index when concerning characterizing the performance of precision reducers, and it is usually required to be measured and evaluated. Apart from that, the efficiency value at the rated torque in the efficiency curve is taken as the evaluation value of the efficiency characteristics of precision reducers. However, at present, the research on the efficiency characteristics of precision reducers mainly focuses on theoretical analysis, the development of measurement devices and the measurement methods, while the analysis model of the efficiency curve has not yet been established. In this context, from the perspective of transmission efficiency measurement and evaluation of precision reducers, the efficiency calculation model of precision reducers is established in this paper. Besides, based on the essential change law of the efficiency curve, the efficiency curve analysis model is also set up. To be specific, taking a certain type of RV (rotate vector) reducer as an example, the actual measurement experiments are carried out, and the efficiency curves at different speeds are obtained. The results show that the efficiency of the precision reducer is affected by the measured speed and load torque, and has a positive correlation with the load torque and a negative correlation with the speed. Then, it is proved that the efficiency curve model proposed in this paper can accurately describe the change law followed by the efficiency curve of precision reducers, thus laying a theoretical foundation for the efficiency measurement and evaluation of precision reducers.
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    Topics: Electrical Engineering, Measurement and Control Technology
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