2024 Vol. 68, No. 3

Research Progress
Research on Performance Testing Methods for Unmanned Aerial Vehicles
CHEN Yuefei, WANG Li, LI Hua, HU Hao, CAO Xiongheng, JIANG Xiaolin, LIU Rongchang
2024, 68(3): 3-14. doi: 10.12338/j.issn.2096-9015.2023.0327
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Abstract:
Unmanned aerial vehicles (UAVs), as versatile aircraft, are widely used in various applications, including monitoring and forecasting of land and marine climate, monitoring and treatment of forest pests and fires, monitoring and control of agricultural pests, monitoring and warning of geological disasters, exploration and positioning of geological and mineral storage, search and rescue of missing persons, national defense security, and intelligent cluster performances. The stability, reliability, and safety of UAVs are essential for providing accurate forecasting, early warning, treatment, exploration, and rescue results. With the rapid development of the UAV industry, the performance of UAVs varies greatly, making it necessary to implement performance testing. Combining current domestic and international UAV-related standards, this article analyzes key factors that affect UAV flight stability, reliable data transmission, precise navigation and positioning, and adaptability to climatic and electrical environments. It explores testing methods and provides a performance testing basis for UAVs to safely and reliably complete command objectives under different environmental conditions.
Research Progress on CO2 Isotope Measurement Based on Infrared Absorption Spectroscopy
LI Gengyu, MA Ruomeng, ZANG Jinliang, MA Luyao, LIN Hong
2024, 68(3): 15-21. doi: 10.12338/j.issn.2096-9015.2024.0077
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Abstract:
The global warming situation has intensified, and greenhouse gas emissions are one of the key factors. Carbon dioxide, as the main greenhouse gas (GHG), requires high-precision monitoring technology as the basis for GHG tracking. On this basis, monitoring the carbon dioxide isotope composition not only enables high-precision concentration monitoring but also allows for distinguishing the contributions of different emission sources to the carbon cycle process, achieving the tracking and traceability of anthropogenic and natural emissions. Developing high-precision carbon dioxide isotope monitoring technology is of great significance for improving the accuracy of carbon emission inventories and optimizing carbon emission reduction measures. In nature, carbon isotope gas concentrations are usually on the order of 10−6 of atmospheric concentrations and are affected by measurement conditions, which leads to increased difficulty in carbon isotope measurements. This paper reviews the research progress of infrared absorption spectroscopy techniques for measuring carbon dioxide stable isotope concentrations, analyzes the principles and research progress of high-sensitivity frequency-stabilized cavity ring-down spectroscopy (FS-CRDS), and provides an outlook on the future direction of stable isotope spectroscopy research. As an emerging optical detection technology, FS-CRDS overcomes the shortcomings of traditional methods, such as insufficient measurement accuracy and low sensitivity, and may become a new generation of standard methods for measuring GHGs and isotope abundance.
Measurement Methods and Techniques
Machine Vision-Based Measurement Method for Determining the Parameters of Low-Frequency Shakers
CHEN Xiankai, YANG Changhong, QIU Yuhan
2024, 68(3): 22-28. doi: 10.12338/j.issn.2096-9015.2023.0364
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Abstract:
To ensure the accuracy of performance parameter measurements and reduce the cost and complexity of low-frequency shakers, a machine vision-based method for determining the parameters of low-frequency shakers is proposed. First, the guide rail is modeled as a large-radius arc, and the displacement change of the feature marker in the vertical direction is analyzed. The bending condition is then fitted using the least squares method to measure the bending degree of the guide rail. Next, the subpixel-level edge extraction method is applied to the region of interest in the motion sequence images to accurately measure the motion displacement of the shaker table. Finally, the sine approximation method is used to fit the motion displacement of the shaker to obtain its fitting amplitude, which is then used to solve the key performance parameters of the shaker. Furthermore, high-precision measurements of these parameters can be achieved using a simple set of visual measuring devices. Comparative experimental results with traditional measurement methods show that the bending degree obtained by the machine vision method is highly similar to that of the traditional method when three different loads are added. For the measurement of other performance parameters, the machine vision method can also obtain reliable measurement accuracy and efficiency in the range of 0.01-10 Hz.
A Simplified Narrowband Frequency-Domain Active Noise Control Algorithm without Secondary Path Modeling
GAO Yuan, GAO Min, YU Guoliang
2024, 68(3): 29-37. doi: 10.12338/j.issn.2096-9015.2023.0319
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Abstract:
For narrowband active noise control (ANC) systems with high sampling frequencies, a simplified narrowband frequency-domain ANC algorithm is proposed that does not require secondary path information. This algorithm directly calculates the amplitude and phase information of the frequency bins corresponding to the reference signal and error signal in the frequency domain by substituting the reference signal sampling points into the discrete Fourier transform (DFT) definition. These frequency bins are evenly divided into multiple sub-frequency bin groups. For each sub-frequency bin group, the optimal update direction for the adaptive filter coefficients is chosen from the four directions of 0°, 180°, and ±90° to achieve narrowband noise reduction. Compared to the FDFxLMS algorithm, the proposed algorithm avoids the participation of all full-band frequency bins in the calculation, thereby improving computational efficiency. When the number of effective frequency bins meets certain conditions, the computational complexity can be reduced. Simulations using single frequency, multi-frequency, and narrowband noise as primary noise sources demonstrate that the proposed algorithm maintains good noise reduction performance while exhibiting excellent stability and tracking characteristics.
Loudspeaker System Identification Based on Adaptive Gradient Descent Algorithm
CAO Nan, ZHAO Lei
2024, 68(3): 38-44. doi: 10.12338/j.issn.2096-9015.2023.0346
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Abstract:
In loudspeaker model parameter identification, the conventional fixed-step gradient descent algorithm is time-consuming and often unstable when the initial parameter error is large. Therefore, a variable-step gradient descent algorithm for identifying speaker system parameters in the frequency domain is proposed. The adaptive method monitors the trend of the parameter identification process and adaptively adjusts the corresponding learning rate, eliminating the need for manual adjustment. Additionally, since directly calculating the gradient of a complex model is challenging, a central difference method is employed to approximate the model's gradient. By establishing a dynamic loudspeaker model and setting different initial values and iteration error termination criteria, the convergence and identification performance of the fixed-step method, least squares method, and adaptive-step method are compared. Micro loudspeakers are used for testing and verification. Simulations and experiments demonstrate that the proposed method has higher efficiency and better robustness to initial errors, exhibiting superior adaptability and universality.
Research on the Construction of Standardized Test Datasets Based on Characterization Parameters
CAI Xiangyu, HE Xiaomei, QU Jiansu, YU Pu, JIA Changyi
2024, 68(3): 45-51. doi: 10.12338/j.issn.2096-9015.2023.0288
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Abstract:
The fitting of geometric elements is a critical step in evaluating errors in measurement evaluation software. Different approximation methods, evaluation strategies, and the rounding of significant figures can all influence the evaluation results, leading to inconsistent outcomes from different measurement analysis software for the same measurement data. To address the difficulty in certifying the evaluation algorithms for geometric element fitting, this paper analyzes and discusses the basis and rules for generating standardized input test datasets. Characterization parameters for different geometric elements are determined, enabling the dynamic construction of standardized input test datasets based on these parameters. Using the standardized input test datasets, the least squares double fitting algorithm and geometric tolerance evaluation algorithm are studied to generate standardized output test datasets. The evaluation results are then compared and verified with Zeiss' CALYPSO measurement analysis software. By comparing the dynamically constructed standardized output test datasets with the evaluation results from the measurement evaluation software, the certification of the least squares fitting-based evaluation algorithms for different geometric elements in the measurement evaluation software is completed.
Measuring Instruments and Systems
Development of a Calibration Device for Vibrating Wire Strain Gauges Based on Hydraulic Drive
LI Ting, YANG Lu, CHEN Xiaping, WANG Mengqi, ZHANG Yongjun
2024, 68(3): 52-57, 37. doi: 10.12338/j.issn.2096-9015.2023.0307
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Abstract:
Traditional vibrating wire strain gauge calibration devices generally use manual or low-power motor drives as the driving force, making it difficult to meet the calibration requirements of vibrating wire strain gauges that require large measurement forces. To address this issue, a hydraulic-driven vibrating wire strain gauge calibration device has been designed and developed. The calibration device can be adjusted within a range of 50-200 mm, and a universal fixture has been designed to achieve clamping and fastening of vibrating wire strain gauges of different sizes, models, and shapes. The device features a compact structure and convenient, labor-saving operation. It has been verified that the hydraulic drive greatly reduces the force required for calibration, while the calibration results remain consistent with traditional strain gauge measurement data. The experimental measurement uncertainty U=0.6% (k=2) is less than 0.7%, meeting the calibration specification requirements.
Design and Verification of a New Sound-Absorbing Composite Board
LUO Benyi
2024, 68(3): 58-61, 74. doi: 10.12338/j.issn.2096-9015.2023.0243
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Abstract:
To address the issue of excessive environmental noise in laboratories, a new type of sound-absorbing composite board was developed. The board has a composite structure consisting of a perforated plate, melamine foam, an asphalt damping layer, glass wool, and a rigid backing (including a skeleton). It exhibits a sound absorption coefficient of no less than 0.6 in the frequency range of 100-5000 Hz. Firstly, Biot's theory was introduced to establish the sound transmission model of the composite board under random incidence of sound waves, and finite element methods were employed to compute the simulation results. Subsequently, a sample of the board was placed in a reverberation room to test its sound absorption coefficient. The test results were consistent with the simulation results, confirming the feasibility of the model. Finally, the sound-absorbing composite board was applied in the environmental noise control project of the Guangzhou Institute of Metrology's thermal laboratory, successfully reducing the indoor noise A-weighted sound pressure level from 79.8 dB to 64.1 dB, further validating the high sound absorption performance of the new sound-absorbing composite board.
Impact Studies in Metrology
Research on Backscatter Peak Measurement Based on CSS-D-60 Type γ Spectrometer
FENG Yanqiang, WANG Tiejian, WANG Haiyang, YU Huaiyuan
2024, 68(3): 62-67, 44. doi: 10.12338/j.issn.2096-9015.2023.0281
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Abstract:
To explore the effectiveness and application of anti-Compton technology in γ spectrum measurements, an anti-Compton measurement study of uranium ore standards was conducted in the laboratory using the CSS-D-60 type anti-Compton γ spectrometer system. Specific measurements were taken for mixed uranium-thorium, uranium-radium equilibrium, and single thorium powder samples. The proportion distribution of Compton scattering photons in the measured spectrum in the energy range of 186-1847 keV for these various samples was obtained. The experimental results show that the proportion of anti-Compton correction data increases with energy, and the correction percentage at the 1001 keV energy peak, which is of interest in direct uranium measurement technology, exceeds 60%. The research results can provide important data references for the development of γ spectrum-based uranium measurement technology and equipment.
A Study of the Effect of Positional Offset on the Calibration Results of the Free-Field Comparison Method
LI Xu, FENG Xiujuan, ZHANG Xiaoli, NIU Feng, HE Longbiao
2024, 68(3): 68-74. doi: 10.12338/j.issn.2096-9015.2023.0305
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Abstract:
Positional offsets of the reference microphone (REF) and the microphone to be tested (DUT) are considered to be an important component causing measurement uncertainty in the free-field comparison method. To assess the effect of positional offset on the sensitivity and frequency response calibration results, this paper quantitatively analyzes the effect of positional offset on the sensitivity level at each frequency by controlling the horizontal and axial offsets of the REF and DUT during the calibration process. A least-squares fit of the calibration results of the sensitivity level to the displacement offset is performed in the frequency range of 250 Hz to 20 kHz, and corresponding fit curves are provided. Statistical tests were also carried out on the fitting results. According to the slopes of the fitted curves and the significance levels obtained from the tests, it is shown that with increasing frequency, the influence of horizontal offset on the calibration results of the sensitivity level increases significantly, reaching a maximum slope of 0.016 dB/mm at 20 kHz. The effects of axial deviation on the sensitivity level vary at different frequency points, with some frequencies being insensitive to axial offset.