Multipoint Measurements Research Articles

Fiber Bragg Grating-based sensor for measuring supersonic inlet terminal shock at different angles of attack

This study presents a multipoint pressure measurement system using fiber Bragg grating sensors to detect terminal shock positions. The system consisted of a fiber optic string encapsulated with multiple diaphragm-based fiber Bragg grating sensors, capable of detecting flow field characteristics at fourteen different axial positions of the inlet. The calibration results indicated a sensitivity of 46.47 pm/kPa, a linear correlation coefficient of 0.9997, and a maximum repeatability error below 1.44%. In supersonic wind tunnel tests, the system effectively measured pressure and located the terminal shock across varying angles of attack and throttling degrees. The maximum difference compared to conventional pressure sensors was 4.7%, and the terminal shock positioning error was limited to 1.2%. Overall, the system has robust multipoint measurement capabilities and is priced at only one-tenth of traditional sensors, showing great potential in the field of inlet measurements.

Observation of Superposition of Cavitation Instability in Liquid Rocket Inducer by Multi-point Pressure Measurement

Abstract The purpose of this study is to investigate the relationship between the growth and contraction processes of each blade cavity and cavitation instability, and to conduct multi-point pressure measurement tests. The experiments will be conducted using cavitation water flow tunnels installed at the Kakuda Space Center of the Japan Aerospace Exploration Agency (JAXA). In the multi-point pressure measurement experiment, a number of pressure sensors are installed in the inducer casing, and the cavity area can be estimated and the cavity length can be obtained by creating a pressure distribution between the blades during the depressurization experiments. This method makes it possible to continuously determine cavity length variation during inducer experiments and to investigate the cavity growth process. In addition, cavity length variation can be obtained with higher time resolution than in visualization experiment, allowing more detailed investigation of the unsteady cavity behaviour during cavitation instability. And two types of superposition cavitation instability were found in this study: one is Super-S R.C. and C.S., the other is Sync R.C. and C.S..

Advanced unconditional signal processing model for cross-section contour reconstruction using multi-channel measurements

In mechanical engineering the standard method to assess the geometric tolerances of rotational parts is by analysing parts’ rotational motion in relation to the measuring system. Traditional tolerance compliance measurement models are conditional signal processing models that require pre-defined contour parameters of measured sections. However, due to part diversity and complexity, pre-determining and pre-setting the section parameters before each measurement process is very time-consuming and, in some cases, unachievable. To address this challenge, this paper proposes a universal unconditional signal processing model, which uses multi-channel measurements for cross-section contour reconstruction that operates without predefined section parameters. This model can handle multi-point measurement signals and accurately estimate the contour shape and engineering center coordinates of measured sections through circumferential Fourier expansion and an approximated signal-contour transform matrix. An efficient iterative algorithm then reconstructs the contour and precisely locates the engineering center. The computational accuracy and robustness of the proposed model have been confirmed through rigorous theoretical analysis and comprehensive experimental validation. Due to its inherent unconditional advantage, the proposed signal processing model can achieve intelligent monitoring of rotational parts throughout their entire life, which not only adapts and remains stable across a wide variety of cross-section types but also significantly improves measurement efficiency, ensuring precise and accurate results.

C-type two-thermocouple sensor design between 1000 and 1700 °C.

At the present stage of transient ultra-high-temperature energy release of boron-containing warm-pressure explosives, single thermocouples are often used for multi-point measurements in the process of their temperature field changes, and the results of their temperature field reconstruction are not satisfactory due to the limited consistency of the thermocouples. Aiming at the above-mentioned problems, a C-type two-thermocouple suitable for transient temperature measurement in high-temperature environments is designed; the system characterization of the two-thermocouple is carried out by using the blind system identification method of the inter-relationships; the identification process is evaluated by a new cost function; and the optimal solution on the new cost function is realized by using the gradient descent method. The temperature reconstruction of the two-thermocouple output excited by the simulated heat source is carried out by using the auto-regressive with extra inputs model, and the feasibility of the reconstruction results is verified. In the experimental part, a thermocouple dynamic characteristic calibration system based on a high-temperature furnace is constructed and experimental validation is carried out in the high-temperature furnace to compare the effects of different exposure lengths and different wire diameters on the output of the two-thermocouple, and as a result, the outputs are corrected and analyzed. The results show that two-thermocouple methods with different combinations of wire diameters are better for temperature measurement, with a reconstructed root mean squared error of 0.0162 and a goodness of fit of 89.13%.

3D-printed electrochemical cells for multi-point aptamer-based drug measurements.

Electrochemical aptamer-based (E-AB) sensors achieve detection and quantitation of biomedically relevant targets such as small molecule drugs and protein biomarkers in biological samples. E-ABs are usually fabricated on commercially available macroelectrodes which, although functional for rapid sensor prototyping, can be costly and are not compatible with the microliter sample volumes typically available in biorepositories for clinical validation studies. Seeking to develop a multi-point sensing platform for sensor validation in sample volumes characteristic of clinical studies, we report a protocol for in-house assembly of 3D-printed E-ABs. We employed a commercially available 3D stereolithographic printer (FormLabs, $5k USD) for electrochemical cell fabrication and directly embedded electrodes within the 3D-printed cell structure. This approach offers a reproducible and reusable electrode fabrication process resulting in four independent and simultaneous measurements for statistically weighted results. We demonstrate compatibility with aptamer sequences binding antibiotics and antineoplastic agents. We also demonstrate a proof-of-concept validation of serum vancomycin measurements using clinical samples. Our results demonstrate that 3D-printing can be used in conjunction with E-ABs for accessible, rapid, and statistically meaningful validation of E-AB sensors in biological matrices.

Experimental study on temperature distribution of double-layer solid cylinder under local heating source

Abstract Heating equipment is widely used in production and life, the transient temperature of the heated object reflects the effect of heating equipment, but also an important basis for the design of heating equipment. In the internal temperature measurement of micro heating equipment, some of the temperature measurement instruments are large in size, which makes it difficult to realize precision measurement, and the use of infrared measurement, laser temperature measurement and other methods cannot be used to accurately measure the temperature of the internal points of the material without destroying the material and equipment at the same time. In this study, based on the thermocouple temperature measurement technology and considering the problem of fragility and breakage caused by the small diameter of very fine thermocouple wires, a multi-point temperature synchronization measurement platform is constructed to realize the precise measurement of the temperature at multiple points inside the micro-heating element. Transient temperatures were measured at different locations of a water-containing porous medium inside a 15 mm long heating element under static heating and dynamic suction conditions in the case study. The results show that moisture and suction have a significant effect on the temperature inside the porous media layer. During the suction process, the temperature drop near the suction opening was larger, and the temperature drop near the wall was about 47% of the temperature drop inside. This study is a guide to the design of heating structures for vacuum drying equipment, electrically heated atomization systems and other micro-miniature heating equipment.

Postoperative maxillary stability after Le Fort I osteotomy using a u-HA/PLLA system: three-dimensional analysis by surface superimposition based on virtual Le Fort I osteotomy

The postoperative stability achieved with Le Fort I osteotomy (LFI) using bioabsorbable systems remains controversial. A new method – multipoint measurement method – was devised for detailed three-dimensional examination of postoperative stability following LFI, and the stability after LFI when using SuperFIXSORB-MX made of u-HA/PLLA was investigated. Thirty-one patients who underwent LFI using SuperFIXSORB-MX were evaluated retrospectively. The patients were divided into four malocclusion types: open bite, mandibular retrognathia, mandibular protrusion, and facial asymmetry. Seven maxillary reference points were measured three-dimensionally using computed tomography scans obtained preoperatively (T0), 4 days post-surgery (T1), and 1 year post-surgery (T2). Surgical changes (T1–T0) and the postoperative discrepancy (T2–T1) of the maxilla were analysed to evaluate postoperative stability by surface superimposition of the virtual LFI segments. Postoperative discrepancy was the largest for the facial asymmetry type, ranging from 0.75 ± 0.45 mm to 0.98 ± 0.52 mm in three-dimensional distance (minimum to maximum mean ± standard deviation values for the individual reference points). The relapse at U1 was 16% in the transverse axis, and the anterior nasal spine moved further upward by 17% of the amount of movement of the maxilla. Fixation with SuperFIXSORB-MX was considered to be within clinically acceptable limits.

Measuring the pose repeatability accuracy of the industrial robot end-effector based on the ISSA-IGCF-IHT method

Abstract Industrial robots play an essential role in intelligent manufacturing. The pose repeatability accuracy of the end effector is an important indicator of the robot's precision operations ability. So, it is essential to measure the pose repeatability accuracy of the end effector. However, most of the existing measurement methods have problems such as cumbersome measurement processes and difficulty realizing multi-point measurements of large spaces. Considering the shortcomings of the existing methods, a theoretical model of the robot end effector’s pose repeatability accuracy measurement is proposed in this paper. Based on the theoretical model, a new method based on an improved sparrow search algorithm-improved Gaussian curve fitting-improved Hough transform (ISSA-IGCF-IHT) algorithm is proposed to measure the Industrial robot end effector’s pose repeatability accuracy. The experimental results show that the position measurement error after compensation is ±1.5μm, and the angle measurement error after compensation is ±2arcsec. We can conclude that the Industrial robot end effector’s pose repeatability accuracy measurement is achieved using the proposed method. The authors' main contribution is that the proposed method’s measurement process is simple and it can achieve multi-point measurement in large spaces. It provides a reference for measuring and evaluating the Industrial robot end effector’s pose repeatability accuracy.

Dynamic correlation between surface carbon response and underlying emissions from spontaneous combustion goaf: field study of an abandoned coal mine

Abandoned coal mine goaf is affected by air leakages and prone to spontaneous combustion, resulting in environmental pollution and geological disasters. Haizhou Open-pit Mine adopts both underground and open-pit mining methods. During the long-term mining process, the original stable stratum structure is constantly destroyed, and the slope slides, increasing cracks and severe air leakage around the goaf and roadway. The spontaneous combustion of coal is particularly prominent after the mine shut down. At present, there is no suitable indirect monitoring method to effectively explore the spontaneous combustion area in goaf. The study developed an all-weather monitoring plan and conducted multi-point continuous long-term measurements of the spontaneous combustion state in one abandoned coal mine goaf located in the eastern part of the Haizhou Open-pit Mine. We evaluated the dynamic correlation between surface CO2 flux (SCF) and changes in the underground fire areas, determined the scope and evolution trend of the fire areas, and identified the distribution and change laws of SCF. The results show a significant positive correlation between SCF and soil temperature; moreover, the SCF value was found to reflect the CO2 emission intensity of the goaf. The high SCF in the test area showed month-wise expansion and increase, while the CO2 emission gradually increased monthly, and the calculated annual total emission was approximately 7017 t. Hence, the study can further provide guidance for the monitoring of spontaneous combustion in shallow coal seams, goaf and the assessment of CO2 emissions from underground coal fires through the on-site monitoring and analysis results.

An algorithm for large-span flexible bridge pose estimation and multi-keypoint vibration displacement measurement

Traditional visual vibration measurement methods face limitations in dynamic outdoor environments, making accurate multi-point vibration measurements challenging for the targeted objects. In this paper, a visual vibration measurement algorithm for large-span bridges is proposed by anthropomorphizing the bridge target and introducing key point detection at the same time. Firstly, the algorithm utilizes a convolutional neural network to extract multi-scale feature information from the image sequence of the bridge model. Secondly, to enhance target detection accuracy, a coordinate attention (CA) mechanism is incorporated, and the shape intersection over union (SIoU) loss function replaces the original loss function. Finally, the algorithm integrates the density-based spatial clustering of applications with noise (DBSCAN) and tracking algorithms to achieve precise localization of bridge targets. Vibration displacement data were extracted from a large-span suspension bridge structure in an outdoor environment and analyzed quantitatively and qualitatively. The vibration displacement curves obtained in this study show the highest level of agreement with the standard displacement signals, with a mean absolute percentage error of 0.5170% for the cable-stayed bridge model, 1.3822% for the Humen Bridge, and 3.2263% and 1.6982% for the Longjiang Bridge.

Design and Application Research of a UAV-Based Road Illuminance Measurement System

This paper presents a UAV-based road illumination measurement system and evaluates its performance through experiments. The system employs a HUBSAN Zino 2+ UAV, STM32F103RCT6 microcontroller, BH1750 illuminance sensor, and GPS and integrates flight, processing, measurement, cloud platform, obstacle avoidance, communication, and power supply units via the OneNET cloud platform. Both hardware and software designs were implemented, using the Z-score algorithm to handle outliers in illumination data. The system showed a single-point measurement error rate of 1.14% and a MAPE of 5.08% for multi-point measurements. In experiments, the system’s horizontal and vertical illuminance RMSE were 1.92 lx and 1.75 lx, respectively. The real-time visualization interface improved operational efficiency, cutting labor costs by half and time costs by nearly four-fifths. UAV control and monitoring from the roadside ensured safety during measurements. The system’s efficiency and wide measurement range enabled extended experiments, collecting illuminance data across multiple horizontal and vertical planes. This resulted in the creation of both horizontal and innovative vertical-plane illuminance distribution maps. These findings provide valuable data for evaluating road lighting quality, enhancing road traffic safety, and improving road illumination design.

Non-interference detection of digital signals in transmission line utilizing quantum sensor of nitrogen-vacancy centers

Digital signals play an extremely important role in the integration and multi-functionality of industrial instrumentation. With the expansion of industrial application scenarios, non-interference detection of digital signals in certain extreme environments has become the need of the hour. This paper demonstrates a method for non-interference Detection of transmission line digital signals based on nitrogen-vacancy (NV) centers in diamond. The optical readability and the sensitivity to magnetic fields of the NV centers are utilized to characterize the current-induced weak magnetic field signals by fluorescence signals in a confined space. By combining quantum sensing technology, quantum imaging technology and electromagnetic induction technology through NV centers, it is able to realize high sensitivity and high precision multi-point measurement and dynamic monitoring of electrical signals. The temporal resolution of the digital signal was evaluated by regulating the duration of the input current in the transmission line, and the lowest transmission current in a single transmission line and two transmission lines in a 1.2 mm × 1.2 mm imaging field of view was explored. The experimental results show that the time resolution of the detected digital signals is up to 30 μs. This research highlights the potential value of NV centers in digital signal processing and provides new research directions for detecting digital signals in extreme environments.

Crucial future observations and directions for unveiling magnetopause dynamics and their geospace impacts

The dynamics of Earth’s magnetopause, driven by several different external/internal physical processes, plays a major role in the geospace energy budget. Given magnetopause motion couples across many space plasma regions, numerous forms of observations may provide valuable information in understanding these dynamics and their impacts. In-situ multi-point spacecraft measurements measure the local plasma environment, dynamics and processes; with upcoming swarms providing the possibility of improved spatiotemporal reconstruction of dynamical phenomena, and multi-mission conjunctions advancing understanding of the “mesoscale” coupling across the geospace “system of systems.” Soft X-ray imaging of the magnetopause should enable boundary motion to be directly remote sensed for the first time. Indirect remote sensing capabilities might be enabled through the field-aligned currents associated with disturbances to the magnetopause; by harnessing data from satellite mega-constellations in low-Earth orbit, and taking advantage of upgraded auroral imaging and ionospheric radar technology. Finally, increased numbers of closely-spaced ground magnetometers in both hemispheres may help discriminate between high-latitude processes in what has previously been a “zone of confusion.” Bringing together these multiple modes of observations for studying magnetopause dynamics is crucial. These may also be aided by advanced data processing techniques, such as physics-based inversions and machine learning methods, along with comparisons to increasingly sophisticated geospace assimilative models and simulations.

Evaluation of Scale-dependent Kurtosis with HelioSwarm

Plasma turbulence involves complex, nonlinear interactions of electromagnetic fields and charged particles across multiple scales. Studying these phenomena in space plasmas, like the solar wind, is facilitated by the intrinsic scale separations and the availability of in situ spacecraft observations. However, the single-point or single-scale configurations of current spacecraft limit our understanding of many properties of the turbulent solar wind. To overcome these limitations, multipoint measurements spanning a range of characteristic scales are essential. This Letter prepares for the enhanced measurement capabilities of upcoming multispacecraft missions by demonstrating that higher-order statistics, specifically kurtosis, as a baseline for intermittency can be accurately measured. Using synthetic turbulent fields with adjustable intermittency levels, we achieve scale separations analogous to those in the solar wind and apply these techniques to the planned trajectories of the HelioSwarm mission. This approach promises significant advancements in our understanding of plasma turbulence.

Temperature compensation of a hybrid algorithm optimized neural network: Application to a 64-channel electronic pressure scanner

As a high-precision instrument, electronic pressure scanners have a crucial role in multi-point pressure measurements. However, the internal piezoresistive components drift with temperature, and this phenomenon has become a key factor restricting the accuracy. In this study, a hybrid algorithm based on back propagation neural network (BPNN) with particle swarm optimization (PSO) and gravity search algorithm (GSA) is reported for multi-channel temperature compensation to solve this problem Fundamentally, the global optimization search capability of GSA and the fast local convergence advantage of PSO are utilized so that the model parameters of the BPNN are guaranteed to be reliable and the efficiency of its execution is further improved. To this end, the temperature data between −40 °C and 70 °C obtained through the calibration experimental system are analyzed for compensation of the electronic pressure scanner from the 0 to 700 kPa adiabatic range. The results show that, compared with BP neural network, radial basis function (RBF) neural network, and PSO-BP method, the new PSOGSA-BP approach has higher accuracy in pressure sensor temperature compensation, in which the absolute error is only 0.2301 kPa and the full-scale error is 0.03% full scale. In addition, the method can be applied to electronic pressure scanners with stronger generalization and demonstrated to be suitable for temperature compensation.

An Improved Multi-point Chord Reference Measurement Device and Error Correction Method for Corrugation Measuring in Sharp Curves

Background: The traditional chord reference method and its device have faced challenges matching the sharp curve track. Thus, it is of utmost importance to research and develop a measurement device and method that can obtain accurate and comprehensive information regarding rail running band corrugation. Aims: It provides a solution for the measurement of the multi-point chord reference method on sharply curved rails and, at the same time, meets the demand for data richness and accuracy in theoretical studies on the causes of rail corrugation and wheel-rail contact relationships. Objective: This paper aims to research and design a measurement device based on the multi-point chord reference method for the rail running band corrugation. Meanwhile, the error in measuring the sharp curve rail is corrected and verified by simulation. Methods: The lateral information of rail running band is obtained by using a line laser profile sensor; the rail corrugation measurement model and error correction model of the rail running band area are established based on multi-point reference system; the simulation of the system model is carried out using Matlab; and the mechanical structure is built for static testing. Results: The measurement model based on the profile sensor and multi-point chord reference system can accurately obtain the rail corrugation waveform of any longitudinal measurement line in the running band area. The measurement results can be accurately corrected for a radius of 200m- 400m, the error parameters can be effectively improved, and the mechanical mechanism of the measurement system runs stably. Conclusion: The results show that the measurement model can accurately measure the rail corrugation of the sharp curve section, and the multi-waveform in the rail running band area has good measurement performance, but the mechanical structure can be optimized and improved in the light weight.

A lightweight convolutional neural network for multipoint displacement measurements on bridge structures

A lightweight convolutional neural network for multipoint displacement measurements on bridge structures

Multipoint temperature measurement system composed of fiber-optic Fabry–Perot interference sensors and a wavelength-division multiplexing filter

A multipoint optical-fiber remote temperature measurement system was developed using reflection-type sensors consisting of a Fabry–Perot interference (FPI) structure with good temperature characteristics combined with a wavelength-division multiplexing (WDM) filter. The FPI sensor was fabricated using a short temperature-sensing region sandwiched between single-mode fibers. FPI optical fibers and a WDM filter functioned as the temperature sensors and wavelength-selective optical source using an amplified spontaneous emission light source, respectively. This system was operated in a dense WDM configuration using an arrayed waveguide wavelength filter.

Spectral power stabilization against temperature variations in multimode fiber Bragg gratings

Fiber Bragg gratings (FBGs) have been extensively used for single-point and multi-point measurements, mostly inscribed in single-mode fibers. However, it is feasible to inscribe FBGs in multimode fibers, which resist bending and can perform discriminative sensing of multiple physical parameters. When using a simple experimental setup to measure the temperature dependence of the dip in the transmission spectrum, significant fluctuations in its spectral power can be observed. Therefore, this study shows that the temperature-dependent spectral power fluctuations in multimode FBGs can be mitigated using a reflectometric configuration with suppressed modal interference, leading to higher-reliability temperature sensing.

Measurement of somatosensory evoked magnetic fields using an adjustable magnetoresistive sensor array

An adjustable helmet-style magnetoresistive (MR) sensor array with room-temperature magnetic flux sensors was developed to demonstrate the simultaneous multipoint measurement of the somatosensory evoked magnetic field (SEF). Utilizing the extended sensor length, we designed the array to permit individual radial adjustment of each sensor, thereby achieving a precise fit to the varied head geometries of different subjects. Furthermore, the geometry of the sensor array precisely adjusted for the individual subject was quickly obtained by calibration. The SEF was measured in three healthy subjects using an array of 30-channel MR sensors placed on the left hemisphere of the head with median nerve stimulation in the right wrist and averaged over 8000 measurements. An M20 component considered to originate from the primary somatosensory cortex was observed at an approximate latency of 20 ms of the magnetic field waveform in all cases (maximum amplitude of 725 ± 257 fT, peak latency of 20.5 ± 0.45 ms). The phase inversion observed around C3 in the international 10–20 system corresponded to the palmar area of the primary somatosensory cortex on the contour map of the magnetic field at the M20 peak. The MR sensor, an affordable and easy-to-use magnetic sensor that does not require a zero-field environment nor a cryogenic apparatus, was successfully used for simultaneous multipoint SEF measurements in humans and provides a promising system for realizing magnetoencephalography application devices.