Combined Measurement System Research Articles

Bandpass filter and frequency-time mapping method for pulse measurement with optical delay.

The pulse signal's transients and low duty cycle characteristics lead to excessive omission and erroneous amplitude measurement in signal capture. We offer a combined microwave photonics frequency-time mapping and optical delay electrical pulse measurement system. Beneficial from the true delay of a long fiber with several paths, the pulse is extended to have a more significant duty cycle so as to boost the capturing possibility. We adopt the bandpass filter to avoid sampling the low-frequency range, prevent phase noise from affecting the signal measurement, and improve the signal-to-noise ratio (SNR). This solves the phase noise issue induced by multiple optical delay paths. The proof-of-concept experiments conduct that a 25 μs pulse with a 50 μs period is stretched to a continuous wave, and the SNR is improved by 7 dB.

Research on error separation method of center of gravity measurement system for large-sized solid of revolution

In order to realize mass and center of gravity measurement of large-sized rotating parts, a set of combined measurement system for center of gravity measurement was developed to adjust the distance according to the length and supporting position of the parts to adapt to different lengths of the measured parts. The study focused on the center of gravity synthesis, error factors and error separation within the system. Firstly, two sets of center of gravity measuring equipment based on multi-point weighing method were used to conduct a joint test on the large-sized measured parts, and the center of gravity measuring model was analyzed. Secondly, the measurement error and its influence on the measurement result are were analyzed when the two sets of measuring equipment were not parallel. Finally, error signals were separated using the multi-step method, Fourier transform and inverse Fourier transform. Simulation experiments show that the residual center of gravity error of Y axis and Z axis is less than 0.3 mm when the tilt angle between two sets of equipment is below 0.3°. The test results demonstrate that the center of gravity measurement error along the X axis is less than 2 mm, which indicates the measurement accuracy better than 0.02% as the length of the test object is about 10 000 mm, and the center of gravity measurement error along the Y axis and Z axis is less than 0.5 mm, which also indicates the measurement accuracy better than 0.02%. These findings indicate that the system enables high-precision measurement of the center of gravity for large-sized rotary products.

PEA–Kerr Combined Measurement Method for Space Charge and Electric Field Distribution of Oil–Paper Composite Insulation

The distribution of space charge and electric field of oil–paper composite insulation is of great importance to the operation and design of converter transformers. However, the widely used pulsed electric-acoustic (PEA) method and Kerr method are difficult to measure the structure of thick pressboard + oil independently. In this article, a PEA–Kerr combined measurement method is proposed. It can not only compensate for each other’s shortcomings but also correct the effects of ultrasonic attenuation on space charge measurement by combining the two measurement signals. By integrating and optimizing the system structure and signal processing methods of PEA and Kerr measurement, the PEA–Kerr combined measurement system is built. The test results show that the system has good linearity, the spatial resolution of the electroacoustic measurement part is 8.8%, and the maximum error of the electrooptic measurement part is 2.5%. Finally, the system is used to measure the structure of 2-mm pressboard + 3-mm oil gap. The relationship between the distribution of space charge and the interface charge density under different voltage amplitudes and polarities is analyzed, and the influence of electric field distortion caused by space charge on the interface charge measurement of oil–paper composite insulation is revealed. This article can provide a basis for measuring and analyzing the distribution of space charge and electric field on thick and complex structures.

An accurate calibration method of a combined measurement system for large-sized components

Large-sized components with numerous supports are essential in advanced manufacturing. Efficient product quality control requires accurate three-dimensional (3D) measurements and error control. For 3D shape and spatial position measurements of the key local features on the support mounting surface, we propose an accurate measurement method combining a global laser tracker, local scanning system, and mobile robot system comprising an industrial robot and a mobile platform. To enhance the measurement accuracy, an accurate calibration method was introduced based on prior knowledge which establishes correlation constraints between local and global calibration. The local calibration method, including rail orientation and extrinsic parameters calibration based on a multi-dimensional combined collaboration target, achieves accurate calibration of both rail orientation and extrinsic parameters. Additionally, the enhanced global calibration method based on multi-dimensional cooperative calibrators constructs correlation constraints among global control points and provides an accurate global measurement field. We constructed a combined measurement system and conducted large-scale measurement experiments. As shown by the accuracy verification results of the proposed system, the maximum and mean measurement errors decreased from 0.142 and 0.132 mm to 0.111 and 0.095 mm within 8 m, respectively, which is highly accurate. Moreover, the large-scale scanning instance of a large-sized spacecraft cabin has also demonstrated that the developed method can significantly expand the measurement range as well as improve the measurement flexibility.

Modelling of ultrasonic method for measuring gas holdup of Oil-Gas-Water three phase flows

In oil–gas-water three-phase flow, the presence of two physically distinct dispersed phases leads to complex interfacial effects and relative velocities between the phases, which poses a significant challenges for gas holdup measurements. In this paper, a novel gas holdup measurement based on flow structure detection is realized. Firstly, the effect of gas bubble diameter on ultrasonic attenuation was studied, and a gas bubble diameter-based ultrasonic gas holdup measurement model was proposed. According to the model's specifications, a combined measurement system consisting of pulse transmission ultrasonic sensor and bi-optical fiber probe sensor was built. The dynamic experiment of oil–gas-water three-phase flow was conducted on a simulated well installation to measure the gas holdup using the combined measurement system. The results suggest that the proposed ultrasonic-optical measurement system can attain a high level of measuring precision.

LOW-INTENSITY SIGNAL MODULATION OF THE MICROWAVE PHYSIOTHERAPY EQUIPMENT

The article describes the features of the amplitude and frequency modulation of the output signals of millimeter range generators for microwave therapy. A review of the appearance of possible biological and medical effects using modulated signals is carried out. The use of highly sensitive radar-type equipment made it possible to study the absorption capacity of a person in the mm-wave range from an external source.
 The authors’s results of experimental studies are described, this are showed that at some frequencies, an increased absorption of the power of the irradiating signal is recorded. These frequencies are referred to as “absorption resonances”. The original schemes of monochromatic and noise signal generators developed by the authors are presented, and the principle of their operation is described. The article shows the possibility of generating low-intensity signals and ensuring the generator range operation using the second harmonic of the monochromatic signal and the selective properties of the EHF nodes. The technical parameters and characteristics of the developed devices are revealed. The application areas of the developed devices in practical medicine are out-lined. With the help of the control unit, a low-frequency signal as a saw-like or triangular voltage is generated and is supplied to the varactor converter. Under the influence of the modulation signal, the varactor capacitance changes, and, therefore, the frequency of the EHF generator. The operation of a combined radiation measurement system with a modulated noise-like output spectrum and the patient feedback is described. 
 The article demonstrates the broad practical possibilities for using microprocessor technology for automation and control of the operation mode selection process, for the formation and change of the microwave signal modulation parameters. The conducted studies reveal the process of interaction of low-intensity microwave radiation with the human body and can be used in technologies of millimeter therapy. The article describes the service functions of the developed equipment, which contribute to its more effective use in microwave therapy technologies.

Calibration and uncertainty analysis of a combined tracking-based vision measurement system using Monte Carlo simulation

A global stereovision system combined with a local vision sensor is an effective approach to large-scale object measurement. However, obtaining the error distribution of such an approach remains a key research challenge in vision metrological applications. This paper investigates the calibration and the reconstruction uncertainty estimation method of the combined vision system. The measurement principle and the calibration method of the transformation matrix between the tracking-based measurement coordinate systems are presented. Furthermore, Monte Carlo simulation is utilized to determine the reconstruction uncertainty based on the theoretical measurement model and the experiment-based input uncertainty. The overall measurement uncertainty of the combined system is found to be 34.5% higher than that of the global vision system, which is more sensitive to the input pixel uncertainty than the local vision system. However, the combined vision system can achieve comparable measurement results within its larger working volume. This work contributes to a better understanding of the measurement uncertainty in combined tracking-based vision systems, as well as providing a few useful practice guidelines for using such a visual system.

Development of a combined navigation and measurement system for manned airborne geophysical measurements

The article is devoted to the idea of combining navigation and measurement software to provide a higher level of efficiency and quality of aerial electromagnetic survey. Complex geophysical measurement systems of “Impulse-Aero” series are overviewed. Current survey technology with the above-mentioned systems includes human-based control of the measurements with a geophysicist on-board. The technology also includes the navigational support by the geophysicist or an additional navigation specialist. The concept of automatic combined complex for navigational and measurement monitoring is proposed in the article. The main goal of the system under analysis is to automatically estimate the quality of received data and to give necessary recommendations on the screen of the navigation unit. As the result of the survey, some tasks during the flight can be solved by pilots without any additional staff. This approach is supposed to increase flight safety, reduce costs and raise the efficiency of the survey in general.

Analytical solution of uncertainty with the GUM method for a dynamic stereo vision measurement system.

Directed at the strong correlation among the input parameters and long measurement chain, which are difficult for uncertainty analysis with the guide of the expression of uncertainty in the measurement (GUM) method, a novel dynamic stereo vision measurement system based on the quaternion theory is presented to reduce the orthogonality restrictions of shafting manufacturing and application. According to the quaternion theory in the kinematic model of the cameras and the analytical solution of uncertainty with the GUM method, the complete, detailed, and continuous uncertainty results of the full-scale measurement space can be obtained. Firstly, one-dimensional turntables and rigid connections are utilized to form the motion cores and the automatic control carriers in the system. Secondly, the novel measurement model is used in the measurement process to shorten the calibration and measurement chains. Once the system based on the novel measurement model is set up, the analytical solution of uncertainty is utilized in the accuracy process. During the analysis process, the strong correlation among the extrinsic parameters is decoupled by introducing virtual circles and the measurement strategy with the GUM method. Through analyzing the relationship among the attitude angles, the major factors which influence the uncertainties in each axis and the final uncertainty are clarified. Moreover, the analytical continuous uncertainty maps for the uncertainties along each axis, combined standard uncertainty, and the expanded uncertainty are illustrated and the uncertainty variation tendency is declared. Finally, the analytical solution of uncertainty with the GUM method proposed in this paper predicts the uncertainty in the full-scale space and provides a new idea of the uncertainty analysis for the complicated combined measurement system.

A Combined Measurement Method for Large-Size Aerospace Components.

Automated and high-accuracy three-dimensional (3D) shape measurement is required in quality control of large-size components for the aerospace industry. To eliminate the contradiction between global measurement and local precision measurement control in 3D digitalization for the key local features of the large-size components, a combined measurement method is proposed, including a 3D scanner, a laser tracker, and an industrial robot used as an orienting device, to achieve high-accuracy measurement. As for improving the overall measurement accuracy, an accurate calibration method based on coordinate optimization of common points (COCP) and coordinate optimization of global control points (COGP) is proposed to determine the coordinate systems. Firstly, a coordinate optimization method of common points (COCP) is recommended. Then, a coordinate optimization method of global control points (COGP) based on the angular constraint is proposed for minimizing the measurement errors and improving the measurement accuracy of the position and orientation of the 3D scanner. Finally, a combined measurement system is established, and validation experiments are carried out in laboratory within a distance of 4 m. The calibration experiment results demonstrate that the max and mean errors of the coordinate transformation have been reduced from 0.037 and 0.022 mm to 0.021 and 0.0122 mm. Additionally, the measurement experiment results also show that the combined measurement system features high accuracy.

Accurate Calibration for Large-Scale Tracking-Based Visual Measurement System

The combination of a large-field-of-view visual positioning system and a local scanning sensor affords an effective approach to the 3-D measurement of meter-scale objects and has been actively investigated by researchers. The calibration of such an integrated measurement system is essential to establish the overall measurement accuracy. This article proposes to calculate the transformation relationship between the local system and the transfer target through the determination of the scales of the combined system. The principle and implementation of this tracking-based combined measurement system are described in this article, as well as the use of the respective scales of the combined system to establish a model of the applicable geometrical relationships. The Kronecker product was used to solve the model equations, after which homogenous transformation matrix optimization was performed. An error model of the camera-based measurement system was also established based on a combination of the image distortion and the working volume. The 2-D and 3-D errors of the local and global sensors were further quantitatively simulated and visualized to demonstrate the calibration accuracy. Standard plane and complex large object measurement experiments were performed to verify the accuracy of the proposed measurement system and its use for the reconstruction of a large shape.

On-road tailpipe emission characteristics and ozone formation potentials of VOCs from gasoline, diesel and liquefied petroleum gas fueled vehicles

Volatile organic compounds (VOCs) of motor vehicles contribute greatly to ground-level ozone formation, especially in the megacity regions. While the variations of tailpipe VOC emissions along with the vehicle technologies and road conditions are rarely investigated systematically. Thus, on-road tailpipe VOC emissions from in-use vehicles, including light-duty gasoline vehicles (LDGV), light-duty diesel trucks (LDDT), heavy-duty diesel truck (HDDT) and liquefied petroleum gas-electric hybrid bus (LPGB), were sampled with a combined portable emission measurement system (PEMS). A total of 102 individual VOC species were quantified by a gas chromatography mass spectrometry detector (GC-MSD), and the maximum incremental reactivity (MIR) scale was used to calculate the ozone formation potentials (OFPs). Results showed that aromatics and alkanes were the major VOC groups regardless of the vehicle type, accounting for 68.1–98.0%. For the LDGV, i-pentane, acetone, and propane were the top three VOC species. Naphthalene, dodecane and n-undecane were main VOC constituents in the diesel exhaust. Acetone was the most abundant VOC species for the LPGB, followed by i-pentane, i-butane and n-butane. Road conditions had a significant impact on the VOC emission factors. Specifically, emission factors on urban roads were 3.3–7.0 times those on the highway. The OFPs were 70.7, 128.1, 2189.4 and 124.7 mg O3/km for the LDGV, LDDT, HDDT and LPGB, respectively; aromatics were the main contributors, occupying 49.6–93.4% of the total OFPs. Results indicated that emission factors and dominant species of VOCs were strongly affected by vehicle technologies and road conditions, but aromatics were the major group for both VOC composition and OFPs.

A new approach for measuring surface hydrological connectivity

AbstractThe development of surface hydrological connectivity is a key determinant of flood magnitude in drylands. Thresholds in runoff response may be reached when isolated runoff‐generating areas connect with each other to form continuous links to river channels, enabling these areas to contribute to flood hydrographs. Such threshold behaviour explains observed nonlinearities and scale dependencies of dryland rainfall–runoff relationships and complicates attempts at flood prediction. However, field methods for measuring the propensity of a surface to transmit water downslope are lacking, and conventional techniques of infiltration measurement are often inappropriate for use on non‐agricultural drylands. Here, we argue for a reconceptualization of the dryland surface runoff process, suggesting that the downslope transfer of water should be considered alongside surface infiltration; that is, there is a need for the “aggregated” measurement of infiltration and overland flow hydraulics. Surface application of a set volume of water at a standardized rate generates runoff that travels downslope; the distance it travels downslope is determined by infiltration along the flow, integration of flow paths, and flow resistance. We demonstrate the potential of such a combined measurement system coupled with structure‐from‐motion photogrammetry to identify surface controls on runoff generation and transfer on dryland hillslopes, with vegetation, slope, surface stone cover, and surface roughness all having a significant effect. The measurement system has been used on slopes up to 37° compared with the flat surface typically required for infiltration methods. On average, the field workflow takes ~10–15 min, considerably quicker than rainfall simulation. A wider variety of surfaces can be sampled with relative ease, as the method is not restricted to stone and vegetation‐free land. We argue that this aggregated measurement represents surface connectivity and dryland runoff response better than standard hydrological approaches and can be applied on a much greater variety of dryland surfaces.

A new 3D laser-scanning and GPS combined measurement system

Terrestrial laser scanning (TLS) is widely used because of its ability to quickly acquire high-density and high-precision 3D image and topographic data. However, it can only acquire independent coordinate system points, which restricts its application in large-scale deformation monitoring. In this study, we constructed a measurement system to acquire global coordinate point cloud data by combining TLS and GPS (Global Positioning System). The coordinate values of retro-reflective targets could be acquired in different coordinate systems, the GPS coordinate and the TLS station coordinate, synchronously. Our experiments showed that, after registration with the homonymy points acquired by 30-min short-baseline differential GPS using the ICP algorithm, the positional accuracy of the TLS retro-reflective target center in the global coordinate was better than 10 mm. This high precision meets, for instance, the requirements of coal mining subsidence monitoring. We used our new combined measurement system to acquire and process the point cloud data of a frame structure. The measurements demonstrated the practicability and robustness of the new measurement system.

Development of Combined Small-Angle X-Ray Scattering and Fluorescence Yield X-Ray Absorption Spectroscopy Measurement Systems for Characterization of Structural and Chemical Information of Pt Alloy Nanoparticle Catalyst

The understanding of the structural and the chemical properties of Pt catalysts in polymer electrolyte fuel cells (PEFCs) is necessary to improve the activity for the durability of the catalysts. The small-angle X-ray scattering (SAXS) and the X-ray absorption spectroscopy (XAS) measurements are widely used to investigate the properties of Pt catalysts. Recently, Povia et al developed a powerful tool by combining the SAXS and XAS measurements for the characterization of the Pt nanoparticle catalysts [1]. However, this technique is difficult to investigate the chemical states of the low-concentrated catalysts. In this study, we developed the combined SAXS and the fluorescence-yield (FY) XAS measurement systems to investigate the structural and the chemical properties of low-concentrated catalysts. The combined SAXS-FYXAS measurement system was developed at BL19B2 in SPring-8. For the XAS measurements, the Pt LⅢ edge was used. The ionization chamber and a single-element Ge solid state detector were used to obtain the FYXAS spectra. For the SAXS measurements, the X-ray energy was set to 11.5 keV and 11.55 keV, which are below and near to the Pt LⅢ absorption edge, respectively. The scattered X-ray was detected using an area detector (PILATUS 2M). The PtCo alloy nanoparticle for the oxygen reduction reaction was used as the sample in this experiment. As the result, we could demonstrate the combined SAXS-FYXAS measurement systems. We will discuss the degradation mechanism of the PtCo alloy nanoparticle catalyst from both SAXS and FYXAS data. [1] M. Povia et al. ACS. Catal., 8, 7000 (2018).

A Convenient Calibration Method for LRF-Camera Combination Systems Based on a Checkerboard.

In this paper, a simple and easy high-precision calibration method is proposed for the LRF-camera combined measurement system which is widely used at present. This method can be applied not only to mainstream 2D and 3D LRF-cameras, but also to calibrate newly developed 1D LRF-camera combined systems. It only needs a calibration board to record at least three sets of data. First, the camera parameters and distortion coefficients are decoupled by the distortion center. Then, the spatial coordinates of laser spots are solved using line and plane constraints, and the estimation of LRF-camera extrinsic parameters is realized. In addition, we establish a cost function for optimizing the system. Finally, the calibration accuracy and characteristics of the method are analyzed through simulation experiments, and the validity of the method is verified through the calibration of a real system.

Novel combined measurement system to characterize film structures by spectral interferometry and ellipsometry.

We propose a novel measurement system to simultaneously measure surface and thickness profiles of thin film structures, which cannot be realized in typical measurement techniques. This measurement is accomplished by combining spectral interferometry and ellipsometry. These two distinct measurement techniques are involved in a single system by the abnormal optical configuration. Further, the measurement results are complementary in order to characterize film structures. Film thickness profiles are measured by spectroscopic imaging ellipsometry and surface profiles are obtained from the spectral phase by spectrally resolved interferometry. This method eliminates the theoretical spectral phase by film thicknesses. The proposed system can determine the dimensional film structures at once, even though they have multi-layered films, substrate textures, and even thin film layers. In the experiments, each measurement principle was fundamentally verified with standard specimens. Further, a 4-layered film specimen was measured in order to reconstruct its 3D film structure. As the result, the repeatability of spectroscopic imaging ellipsometry was less than 1 nm and that of spectrally resolved interferometry was a few nanometers, which dominantly affected the performance of the whole system. Several issues for improving accuracy and precision of the proposed system are also discussed in this paper.

Combination of laser interferometric and laser extinction methods for precise thickness measurement of liquid film between coalescing twin air bubbles

A combined laser extinction and laser interferometric measurement system was developed for the measurement of the change in thickness of a liquid film formed between colliding twin bubbles. The liquid film thickness during the bubble coalescence process is measured based on the bubble approach velocity and the contact duration. The proposed method affords a ten-fold spatial resolution (∼6 μm) of the liquid film thickness distribution compared to the current laser extinction measurement method. Through the use of the proposed method, it was found that the liquid film in the vicinity of its thinnest area immediately before coalescence was wedge-shaped, with the minimum film thickness immediately before coalescence being 0.3–1.3 μm, which is ∼0.6-μm thinner than the value determined by the current laser extinction measurement method. Greater precision of the proposed method is enabled by its improved spatial resolution.

Combined measurement system for double shield tunnel boring machine guidance based on optical and visual methods

In order to detect the position of the cutting shield at the head of a double shield tunnel boring machine (TBM) during the excavation, this paper develops a combined measurement system which is mainly composed of several optical feature points, a monocular vision sensor, a laser target sensor, and a total station. The different elements of the combined system are mounted on the TBM in suitable sequence, and the position of the cutting shield in the reference total station frame is determined by coordinate transformations. Subsequently, the structure of the feature points and matching technique for them are expounded, the position measurement method based on monocular vision is presented, and the calibration methods for the unknown relationships among different parts of the system are proposed. Finally, a set of experimental platforms to simulate the double shield TBM is established, and accuracy verification experiments are conducted. Experimental results show that the mean deviation of the system is 6.8mm, which satisfies the requirements of double shield TBM guidance.

On pressure impulse of a laser-induced underwater shock wave

We experimentally examine a laser-induced underwater shock wave paying special attention to the pressure impulse, the time integral of the pressure evolution. Plasma formation, shock-wave expansion and the pressure in water are observed simultaneously using a combined measurement system that obtains high-resolution nanosecond-order image sequences. These detailed measurements reveal a distribution of the pressure peak which is not spherically symmetric. In contrast, remarkably, the pressure impulse is found to be symmetrically distributed for a wide range of experimental parameters, even when the shock waves are emitted from an elongated region. The structure is determined to be a collection of multiple spherical shock waves originating from point-like plasmas in the elongated region.