Direct current coefficient is an essential parameter of I/V transducer, which directly affects the measurement results. Traditional method, comparing the measured transducer with the standard transducer, has limitations; failure to solve the problem in essence. To measure the direct current coefficient accurately, a measuring device was developed, which consists of direct current source, standard direct current ratio, adjustable standard direct current ratio, standard I/V transducer, voltage meter and null indicator. A measurement method was proposed, which fixes the value of direct current source and current flowing through the standard I/V transducer; adjusts the current through the high accuracy ratio conversion. The error measurement principle was employed to minimize the influence on the measurement results. Measure the current coefficient of an I/V transducer and restore its actual working state. The result shows that the current coefficients in the four current ranges are all negative, and are basically in the order of 10−5. The proposed method is characterized by breaking dependence on the superior standard device and meets the needs of precise measurement result correction.
In order to further support the development of arrayed impedance-based icing detection technology, a temperature drift self-compensation method that does not depend on traditional temperature sensors is proposed for the ice thickness measurement error problem caused by temperature variation. The method achieves compensation by establishing a mapping relationship between relaxation time and temperature to calculate the temperature of the ice layer. A theoretical model to describe the temperature drift characteristics of complex dielectric constant based on the relaxation polarization principle is established, and the ice layer temperature calculation method is proposed on the basis of complex impedance measurement. The experimental results show that the method reduces the error of ice thickness measurement, and the root mean square error reaches 0.09 mm in ice cases below 4 mm, which is clearly better than the uncompensated results.
Surface microwave field imaging is an important method for evaluating the performance of microwave/millimeter-wave monolithic integrated circuits. It is crucial to conduct the detection at the micro-nano scale. In the near-field scanning microwave microscopy system, the local signal of the surface radiation field is coupled with the tip signal, and the S11 curve related to the reflected signal is obtained. The curve exhibits varying degrees of sinusoidal oscillation as the radiation intensity changes at the specified position. The microwave intensity at this point is represented by the peak-to-peak value of the oscillation curve. Finally, the surface microwave intensity is mapped by scanning point by point. This method is crucial for evaluating the reliability of on-chip integrated circuit signal transmission and for the design and manufacture of devices.
Surface extraction from point clouds has many applications in product design, reverse engineering, industrial manufacturing and more. One of the key challenges is the detection and segmentation of overlapping areas of different surfaces. Existing methods are mainly on local judgment of similarity features, which can lead to either over- or under-segmentation. The proposed method in this paper utilizes DBSCAN for 3D point clouds surface extraction and boundary detection. Prior to extraction, the normal vector at sharp features is estimated based on a voting method. The surface extraction process is comprises two stages. First, the local quadric surface is determined based on the candidate sample points, and the points belonging to the same local surface are clustered. Second, in the merging stage, where the local surfaces are combined into a single smooth surface using three merging conditions. To demonstrate its effectiveness, the proposed approach is accessed on synthetic and real datasets, showing that the method can address the problem of insufficient and excessive segmentation of curved point clouds, and achieve high extraction accuracy.
Aiming at the problem that the current test items of China's electric data acquisition and testing laboratory are not in line with the actual use environment. This paper proposes a simulation scheme of electricity information acquisition link based on fault injection technology. Taking the intelligent electric meter as an example, this scheme uses fault injection technology such as signal interference and message tampering to simulate the abnormal working condition information of the field operation, and detects the function, performance and reliability of the intelligent electric meter in this environment. The comprehensive failure rate decreased by 75.64 % in different scenarios. In addition, the research also provides effective data support for the quality evaluation system of electric data acquisition of the intelligent electric meter, which can better meet the needs of electricity information collection in the actual use environment and improve the accuracy and reliability of detection.
For correcting the color difference in machine vision imaging, all colors in the color space are usually used to train the correction model in traditional methods, which will lead to a complex training process of the model, long training time, and can not achieve high correction precision for each color. In order to solve these problems, a local color space correction scheme is proposed in this paper. In the scheme, the total color space is divided into smaller sub-color space based on color difference threshold and space distance respectively, and the colors in the sub-color space is corrected by polynomial regression method. The experimental results show that local color space correction has higher accuracy and more stable performance than total color space correction.
As a primary standard device, the pVTt method gas flow standard device is widely used and has been used as the main gas flow standard in many countries. Chongqing Branch of National Oil and Gas Large Flow Metering Station has established a set of pVTt gas flow standard device with working pressure of (0.1~1.2) MPa, flow range of (14~850) kg/h, Measurement uncertainty of $U_{\mathrm{r}}=0.07\%$ and $k=2$ . The device uses a 2m 3 tank as the standard container and uses 1.2 MPa natural gas stored in two 3300m 3 spherical tanks upstream as the calibration gas. The advantage of this device is that it can operate under positive pressure using natural gas as the medium, and the upstream natural gas source pressure is relatively stable and the gas quality is clean, without the need for additional stabilizing and purifying devices. This device can perform calibration of critical flow Venturi nozzles, mass flow meters, and other gas flow meters with an accuracy level of 0.2 or below under positive pressure using natural gas as the medium. Using this detection standard device, a critical flow sonic nozzle with a throat diameter of $\mathrm{d}=4.770\text{mm}$ was calibrated and the uncertainty of the measurement results was analyzed, resulting in $U_{\mathrm{r}}=0.16\%$ and $k=2$ .
As emerging nondestructive testing technologies, the electromagnetic acoustic and ultrasonic phased array inspection technologies have broad application prospects. By combining these two technologies, the electromagnetic acoustic transducer (EMAT) phased array is of great research significance. When building the model of EMAT phased array, due to the difficulty in solving the three-dimensional multi-physical coupling model, existing literature lacks research on the imaging of two-dimensional EMAT arrays in three-dimensional space. Therefore, this paper established a 3D model of EMAT phased arrays by means of mapping in the multiphysics coupling simulation software COMSOL and carried out simulation solutions. In this paper, firstly, the process of electromagnetic field and elastic dynamic field coupling to generate ultrasonic waves during EMAT operation was derived, as well as the control mode of acoustic beam deflection and focusing in ultrasonic phased arrays. Then, an EMAT transducer array unit was constructed in COMSOL, and a mapping-based simplification was proposed to address the difficulties in constructing a pure 3D model. The calculation results of the electromagnetic field of the 2D axisymmetric model were mapped into the 3D model, thereby achieving the construction of the 3D model under the constraints of computational time and complexity. Finally, based on this, multiple array units were combined to form an EMAT phased array. Models of 1D linear array and 2D planar array were established, and the deflection and focusing of the ultrasonic beam were achieved. The simulation results were compared with the relevant theories to verify the accuracy of the modeling, thus confirming the feasibility of building a 2D-3D Mixture model by mapping.
In response to the demand for rapid and high-precision measurement of aircraft parts, this article proposes an aircraft part detection device based on machine vision measurement, it device has been selected and arranged for the ball screw slide used for measurement. The overall system of the sliding platform and stage has been designed, using machine vision detection technology to collect data and images, feature extraction and part classification are performed on the edges of parts, achieving fast and high-precision measurement of aircraft parts. This article discusses the main composition, working principle, and implementation steps of the visual inspection device for gantry aircraft parts, the structural parameter design and strength verification of the ball screw slide and measurement area, as well as the selection of visual systems. On this basis, through finite element analysis, the key component models are effectively analyzed and validated, proving that the visual inspection device for gantry aircraft parts can meet the design requirements.
As a trade handover tool, the accuracy of flow meters directly affects factors such as customs clearance efficiency and enterprise cost accounting. It is necessary to regularly verify or calibrate the flow meter. However, during calibration, installing flowmeters with different residual media on the calibration device can cause pollution to the calibration medium of the calibration device. Rechecking the flow rate with contaminated media can also cause pollution to the tested flowmeters. Toxic and harmful media can cause secondary pollution with the use of the tested flowmeters, bringing incalculable secondary disasters. Although there are currently multiple methods for cleaning flow meters, each has its own advantages and disadvantages. Based on the characteristics of flow meter cleaning, this article conducts research on a fully automatic flow meter cleaning device. The device adopts advanced computer control technology, frequency conversion control technology, ultrasonic cleaning technology, sensor technology, medium environmental protection treatment technology, etc. The entire cleaning process is completely controlled by a computer, automatically completing the switching of cleaning media, adjusting the intensity of ultrasonic cleaning, starting and stopping the circulating pump, and adjusting the flow rate The adjustment of cleaning medium temperature and the determination of instrument cleanliness, while cleaning the instrument, the generated waste liquid is separated and reused, truly achieving full automation and pollution-free, solving the problems of narrow applicability, low cleaning efficiency, and easy environmental pollution of the current flow meter cleaning method. At the same time, the research and development of this device can serve the construction of oil and gas flow measurement capacity in the Zhejiang Free Trade Zone, ensuring the accuracy and reliability of key trade transactions such as industrial oil products and bonded fuel.
The high accuracy time delay calibration of UTC(NTSC) replicating device is essentially a method to calibrate the delay of the device. Segmented calibration is used for the delay of the UTC(NTSC) replicating device. It combines relative calibration and absolute calibration, and a method of relative calibration for the delay of the device based on UTC (NTSC). Absolute calibration refers to demarcate the time delay of the antenna cable. Relative calibration refers to demarcate the time delay of the signal transmission delay and the receiver delay within the device based on UTC (NTSC). Specifically, UTC (NTSC) is used as the reference signal, and the time measurement equipment is used to measure the time bias between the PPS reproduced by UTC(NTSC) replicating device and UTC (NTSC), and the clock bias is calculated between the UTC(NTSC) replicating device and the reference equipment in the same time period. Thus, the relative delay of the UTC(NTSC) replicating device can be obtained, that is the time bias deducting the clock bias by collecting for 24-hour. By calibrating the device delay method, the timing accuracy of the UTC(NTSC) replicating device can be accurate to 0.2 ns.
In order to solve the problem that the measurement of sea current flow direction of HF surface wave radar is inaccurate due to the using of theoretical antenna pattern to calculate sea current, thus lead to the insufficient measurement accuracy of vector synthetic sea current field, which is difficult to meet the requirements of high-precision ocean observation. The design idea of HF surface wave radar antenna pattern measuring control unit based on DDS technology is proposed in this paper. This unit is composed of a DDS chip, a power control module, a MCU, a communication interface and other parts. The operating frequency can be adjusted according to the actual working frequency band of radar. After the hardware scheme is proposed, the software flow of measuring control unit is designed. The reliability of system software is verified by testing, and the mechanism analysis is carried out on the deficiencies of the hardware design. The optimized test results show that: The measuring control unit of HF surface wave radar antenna pattern can respond to remote control instructions from the host computer or digital transmission radio in real time, and parameters such as frequency, amplitude can be set. It is suitable for loading on an unmanned ship. It has the characteristics of high frequency resolution, stable transmitting power and good practicability. It has important application value to effectively improve the accuracy of sea current observation by HF surface wave radar.
The positioning accuracy of the Loran-C signal will be interfered with by the aliasing of sky and earth waves. Separating the skywave and groundwave with appropriate methods can effectively improve positioning accuracy. In this paper, we propose the eigendecomposition spectral analysis technique based on fourth-order cumulants to calculate the delay of the Loran-C skywave. Their accuracy is compared with that of traditional eigendecomposition spectroscopy. At the same time, the analysis results based on the actual collected data are given. The results show that the new technology can effectively suppress the influence of Gaussian noise, the wave generated by noise is 80% lower than the traditional algorithm, effectively reduce the effect of noise, can more accurately identify the skywave delay, and expand the number of arrays to twice the conventional algorithm, which makes the technology can effectively reduce the interference of other Loran-C signals. In a bad environment, the algorithm can still have good positioning accuracy and anti-interference ability.
Due to the issue of fault recognition, in order to achieve a higher matching rate between samples and labels, it is necessary to be able to extract richer fault feature information. Therefore, a CWT-2D-CNN bearing fault intelligent diagnosis method is proposed. Firstly, the one-dimensional vibration signal collected is transformed by CWT to construct a two-dimensional image with rich time-frequency information, which is used as the input of the 2D-CNN network, enabling the network to learn as much as possible about the fault time-frequency feature information. Secondly, through deep convolutional pooling layers, further dimensionality reduction of the results from the previous step is a necessary step, which can reduce the difficulty and parameters of optimization and further reduce information redundancy. In the last, the network structure is optimized through backpropagation algorithm to construct an integrated framework model from the extracting feature, decreasing dimensionality to classifying of fault signal. Through fault classification experiments under different states, the model achieves an identification accuracy of 97.98% for faults and can accurately discriminate fault states, verifying the effectiveness of the method, which can serve as one of the inspiration sources for future intelligent diagnosis directions.
With the continuous development of national telecommunication technology, there is an urgent requirement to deploy high quality time-synchronizing systems in different distribution scenarios, such as 5G Communication, Smart Grid, and Astronomical Monitoring, in order to satisfy various requirements, such as improving wireless space spectrum utilization and PMU steady-state accuracy. Currently, the emerging WR technology can achieve sub-nanosecond synchronization errors. However, it still has some drawbacks, such as the large time fluctuation required for synchronization and the difficulty in fine-tuning the link delayed compensation. Thus, the paper designs and implements a high precision time- synchronizing system with FPGA as the main control chip, which can guarantee synchronization errors better than 1 ns and accuracy better than 100 ps in the 10 km fiber transmission distance, control the time required for synchronization within the 20 s by algorithm improvement, and make the time delay compensation resolution up to 20 ps.
Aimed at the requirements of communication optical power meter, on the basis of analysis about the technology at home and abroad, the calibration technology of optical power meter is studied. An optical power meter calibration system is designed. It is mainly composed of optical power meter, high stability light source, attenuator and so on. It can realize the calibration of correction value and nonlinear degree of communication optical power meter. High stability light source is developed. Multi-wavelength integrated single optical port output is realized by using the scheme of ‘wavelength division multiplexing + discrete control’. The scheme of 'automatic power control + automatic temperature control + coherent suppression’ is adopted to improve the stability of the light source. The dynamic and continuous adjustment of optical output power is realized by using the scheme of ‘collimated beam expansion + attenuator’. The light source has the characteristics of multi-wavelength, high stability, and has the functions of output adjustment indication and modulation. The uncertainty of the system is analyzed and evaluated in detail. The system can calibrate the correction value and nonlinearity of the optical power meter with the power measuring range of -60dBm to +10dBm and wavelength point of 1310nm and 1550nm. The modified extended uncertainty U=3% $(k=2)$ and the nonlinear degree extended uncertainty U=0.4% $(k=2)$ . The practical application shows that the system is reasonable in design, reliable in use and stable in performance. It can be used as the standard equipment of optical power meter.
This study explores a dynamic analysis method for evaluating measurement uncertainty in the measurement process by calculating the distribution of measurement uncertainty at multiple measurement points within the measurement range. The analysis method provides an intuitive and visual representation of the measurement uncertainty, given a mathematical model and equipment configuration. A wind tunnel device with a Pitot tube as a standard was used to analyze the uncertainty of the flow velocity measurement. The dynamic analysis method was applied to assess the uncertainty of the measurement results and compare the measurement uncertainty of different differential pressure transmitters with various measuring ranges. The transmitter configuration was optimized to improve the measurement accuracy.
In view of the current lack of research on the conformity determination of the measurement results of wind direction sensors in automatic weather stations. According to the working principle of the EL-2C automatic weather station wind direction sensor, a corresponding experimental scheme is designed, and a corresponding measurement model is established according to its experimental process. The uncertainty of its measurement results is evaluated using the GUM method. The expanded uncertainty $U$ and $U_{95}$ values of the corresponding error values for each measurement point are obtained in the range of $(2.1^{\circ}\sim 2.6^{\circ})$ and $(2.2^{\circ}\sim 2.6^{\circ})$ respectively, and the results meet the basic requirements for evaluating the error compliance of the measuring instrument. This method fills the gap in the current research on the conformity determination of wind direction sensor measurement results at automatic weather stations, improves the reliability of wind direction sensor measurement results at automatic weather stations, and provides technical support to ensure the accuracy of wind direction detection data.
When global navigation satellite system navigation signals are restricted or unavailable, using the inertial measurement unit and magnetometer of a smartphone for pedestrian dead reckoning (PDR) is a simple and highly practical navigation positioning solution. Since heading estimation is the main source of error in PDR positioning, this paper proposes a correction scheme based on the Long Short Term Memory (LSTM) neural network to solve the problem of heading angle estimation errors when using a smartphone for PDR. The proposed F-LSTM (Fully Connected LSTM) network is trained on data collected in various heading directions to regressively approximate the non-linear sensor error. The data collection is relatively small, and the training time is short, which improves the practicality of the model. Experimental results show that the proposed algorithm can effectively improve the accuracy of heading angle estimation, with the heading estimation error less than 4°. The algorithm is integrated with classical PDR. The positioning error that is less than 2.44 % of the total distance.
In order to meet the needs of users for standard time frequency signals, the National Time Service Center Time frequency Laboratory has established a set of standard time remote replication system, and its users are distributed in multiple sites across the country. The regular working mode of the system is point-to-multi-broadcast service, which puts forward higher requirements for the reliable and stable operation of the reference terminal. Aiming at the limitations of the existing standard time remote replication system, this paper proposes a standard time replication method based on the fusion of multi-reference terminals, which not only solves the problem that a single reference terminal cannot guarantee the continuity and stability of the system in the event of sudden anomalies, but also finds that the recurrence capability of multi-reference terminal fusion is superior to that of a single reference terminal through comparative test and experiment. The results show that the standard deviation is increased from 1.3ns to O.55ns, and the peaking value is increased from 10.74ns to 3.57ns, which can meet the high precision and high reliability requirements of users for standard time-frequency signals.
