High-precision Measurement Method Research Articles

An Optimized Design Method for Magnetometer Targeting High-Precision Measurement of Quasi-Periodic Magnetic Field Signal

An Optimized Design Method for Magnetometer Targeting High-Precision Measurement of Quasi-Periodic Magnetic Field Signal

Accurate density measurement of a small solid sample using a combination of hydrostatic weighing and pressure-of-flotation methods

Abstract A new high-precision density measurement method for small non-silicon samples was developed. Hydrostatic weighing (HW) and the pressure-of-flotation method (PFM) are high-precision techniques for determination solid sample densities. However, in HW, the uncertainty of the density measurement is quite large when the volume of the sample is much smaller than that of a 1 kg silicon sample owing to the uncertainty of the auxiliary weights during the measurement. Additionally, the PFM is not applicable for measuring the density of non-silicon materials. We developed a new method that combines HW and the PFM. We prepared a small 45 g Si3N4 sphere sample with a diameter of 30 mm. By employing two silicon discs with these masses that were nearly equivalent to the apparent masses of the sample, the same auxiliary weights were used for both the standards and the sample. The new method was validated by measuring the density of the 45 g Si3N4 sphere with a relative standard uncertainty of 4.6 × 10−6, which is significantly lower than that obtained by traditional HW methods. This approach demonstrates substantial improvements in the precision of small-sample density measurements, thus offering a robust alternative to conventional techniques.

Miniaturized laser interferometer using dynamic current-wavelength modulation for high precision displacement measurement

Abstract This study proposes a compact displacement measurement interferometer facilitated by a novel dynamic current-wavelength modulation method for high-precision displacement measurement. This technique compensates for the modulation depth by precisely predicting the optical path difference with frequency-scanning interferometry to achieve consistent modulation depth over an extensive measurement range. Additionally, a wavelength-locking method was developed for the 1550 nm band, using the P7 absorption peak of hydrogen cyanide gas to lock the central wavelength of the laser. The experimental results showed that the wavelength stability can be kept within 128 fm for 8 h with the proposed method. Furthermore, the deviations are less than 40 nm compared to a calibrated laser interferometer within the 300 mm measurement range. This research offers precise positioning feedback for precision engineering, paving the way for advanced semiconductor manufacturing processes.

Research on High-Precision and Wide-Range Spacecraft Potential Measurement Method Based on Capacitive Voltage Division.

The charging and discharging of satellite surfaces induced by the space plasma environment constitute a primary cause of spacecraft anomalies, particularly in geosynchronous orbits subject to geomagnetic substorms and hot plasma injections from the magnetotail, where satellites are prone to unequal high-potential charging, significantly impacting the safe and reliable operation of spacecraft. Addressing the need for measuring these unequal charge states, a high-precision, wide-range spacecraft potential measurement method based on capacitive voltage division was investigated. This study analyzed the mechanism of potential measurement and the factors contributing to errors during the measurement process, explored optimal design methodologies, and innovatively developed a fundamental charge zeroing method to resolve output drift issues caused by accumulated errors fundamentally. Consequently, a non-contact potential measurement system was developed, featuring a measurement range of up to -15,000 V, a resolution below 15 V, and a nonlinear error of less than 0.1%. This system provides technical support for monitoring the potential state of spacecraft and ensuring their safety and protection.

High-Precision Measurement Method for Small Angles Based on the Defect Spot Mode of the Position-Sensitive Detector.

The paper proposes and verifies a small-angle measurement method based on the defect spot mode of the position-sensitive detector (PSD). With the output characteristics of the PSD in the defect spot mode and the size transformation properties of a focused beam, the measurement sensitivity can be significantly improved. Calibration experiments with the piezoelectric transducer (PZT) indicate that compared with the current PSD-based autocollimation method, the proposed method can improve the sensitivity of small-angle measurement by 57 times, and the measurement sensitivity of the proposed method can be further improved by optimizing the system parameters, while the proposed method has the advantages of a simple system and high real-time performance. Therefore, the proposed method is expected to be used in high-precision motion error detection, as well as in shape and position measurement.

Experimental study on high-precision measurement of surface temperature in friction stir welding aluminium alloy 2219 based on infrared thermometry

In friction stir welding (FSW) of aluminium alloy 2219, the welding temperature critically influences the weld quality. Accurate measurement of the welding temperature is essential for effective welding process control. However, the conventional approach of non-contact infrared thermometry faces significant challenges in FSW due to the inherently low and variable emissivity of aluminium alloys, making it susceptible to environmental radiation interference. This paper proposes a novel, high-precision method for measuring the surface temperature of FSW aluminium alloy 2219 based on infrared thermometry principles. Initially, the study delves into these principles, analysing factors that affect the accuracy of infrared thermometry in the context of FSW in industrial settings. To enhance the surface emissivity of the weldments, a high-emissivity coating is applied to the aluminium alloy surface. Additionally, strategic adjustments in the positioning of the thermal imager and careful selection of the measuring area effectively mitigate interference from the FSW tool’s radiation. Conventional methods report a temperature measurement error greater than 2%, while the proposed method reduces this error to 1.2%. The effectiveness and practical utility of the method are validated through FSW experiments on flat plates and rocket tank rings, corroborated by comparative analyses with surface thermocouple temperature measurements. This confirms the viability of the proposed method for high-precision temperature measurement in aluminium alloy FSW applications.

Research on Nanometer Precision Measurement Method of High Order Even Aspheres

Optical aspheres are demanded with extremely high precision to meet functional requirements in space telescopes, extreme ultraviolet lithography, and other modern large optical systems. The nano-precision fabrication of optical aspheres requires high-precision measurements to guide deterministic optical processing. Null test is the preferred method for high-precision measurements. Null optics are required to compensate for the incident wavefront in the null test of optical aspheres. However, wavefront aberrations caused by the transmission flat or transmission sphere of interferometer and null optics can limit measurement accuracy and need to be separated. A nano-precision measurement method is proposed for the even optical aspheres of high order in this paper. A computer-generated hologram is used as a null optic to realize a null test on optical aspheres. Mapping distortion correction is performed on the measurement results to ensure that the transverse coordinates of the measurement results correspond correctly to those of the test surface. Absolute testing is applied to separate the wavefront aberrations caused by the computer-generated hologram and interferometer optics. Finally, the results obtained by this method were used to guide deterministic optical processing, enabling the nano-precision fabrication of optical aspheres.

High-precision dynamic axial clearance measurement method based on an all-fiber heterodyne microwave-AMCW with an all-phase tracking algorithm.

Rotor-stator axial clearance is critical to the safety and efficiency of major rotating machinery. However, factors such as high-speed rotation, narrow space, high temperature, and vibration present significant challenges for high-precision dynamic measurement of axial clearance. This paper proposes an axial clearance measurement method based on an all-fiber heterodyne microwave amplitude-modulated continuous wave (microwave-AMCW) system combined with an all-phase tracking algorithm, characterized by high precision, wide bandwidth, and a large measurement range. To mitigate environmental influences, a heterodyne all-fiber microwave-AMCW optical path structure is developed, and a compact dual-core fiber sensor probe is designed. The all-phase tracking algorithm is introduced to enhance dynamic precision and expand bandwidth. Additionally, what we believe to be a novel bandwidth test method based on time division multiplexing is proposed to evaluate the system's wide-bandwidth performance. The proposed system's performance is validated through simulations and experiments. The results demonstrate that the system exhibits excellent resistance to environmental interference, with a measurement range up to 24.5 mm and a static precision better than 4.5µm. Dynamic experiments further confirm the algorithm's effectiveness, achieving a precision better than 5.3µm at 100kHz bandwidth. Compared to other clearance measurement algorithms including the Hilbert transform and FFT, the proposed method reduces dynamic error by over 74%.

High-precision spatial measurement method of accelerator pre-alignment based on multiple total stations

Abstract With the development of accelerator technology, the scale of accelerators is becoming larger, ranging from hundreds of meters to several kilometers. For stable operation of accelerators, high-precision alignment, positioning, and installation are crucial. Installing all equipment inside the tunnel poses safety risks as personnel would be in a closed environment with potential radiation exposure for prolonged periods. To address the challenges of long adjustment and maintenance periods inside the tunnel due to the installation of equipment for large-scale accelerators, most accelerator devices under construction or in research have pre-alignment assemblies. Each assembly consists of a certain number of magnets distributed on girders. The magnets in one unit are pre-aligned with high precision in the laboratory and then transported to the tunnel. Aligning the entire magnet girder can significantly improve installation efficiency inside the tunnel. To meet the pre-alignment accuracy requirement of 10 μm in the horizontal and vertical directions for the magnet units in the high energy photon source (HEPS) storage ring, a system for high-precision pre-alignment of accelerator units using four total stations for angle observation has been designed in this paper. By employing different instrument layout configurations and incorporating reliable distance benchmarks, high-precision pre-alignment of the magnet are achieved. By arranging targets and utilizing recognition for automatic targeting, real-time point calculations during pre-alignment enhance efficiency. Subsequently, based on this system, pre-alignment simulation calculations and experimental verification of eight magnet focusing–defocusing units in the HEPS storage ring are conducted and ultimately realizing the 10 μm transverse and vertical pre-alignment measuring error within the units. This method, based on high-precision measurements in a small-scale space, reduces the period required for personnel on-site and improves pre-alignment efficiency. It also provides a reference for pre-alignment of multiple magnet units in large accelerators such as the Southern Advanced Photon Source and Circular Electron Positron Collider.

Effect of micrometer bubble interfaces on the detection and measurement method of XLPE

Hidden air bubble defects in the XLPE (Cross-Linked Polyethylene) insulation will seriously affect its electrical performance, which needs to be detected timely to ensure the safe and stable operation of the power system, but the interfaces between bubbles and XLPE may affect the detection. This paper proposes a novel method for high-precision detection and measurement method of micron-sized bubbles in XLPE based on THz time-domain reflection technology. To analyze the influencing factors limiting the high-precision detection and measurement of micron-sized defects, firstly, the propagation law of THz wave in XLPE with and without defects is studied, and the unipolar and bipolar pulses reflected at the defects are analyzed by overlap, and then a new method of micron-sized defects detection and measurement is proposed based on the overlap property of the bipolar pulses, and the relationship between the minimum detecting frequency and the size of the defects in the various detecting methods is determined. And the finite element method is used to simulate the THz detection of XLPE samples with defect thicknesses of 100, 7, 5, and 3 μm, respectively, and the proposed method is validated in conjunction with experiments. The results show that micrometer defects can be detected and measured with high precision using this proposed method, and the error can be controlled within 4.39%, which is significantly better than the conventional detection method. The proposed method can provide a new idea for non-destructive testing of insulation defects.

High-Precision Measurement of Microscales Based on Optoelectronics and Image Integration Method.

Currently, there are various types of microscales and the conventional line detection system usually has only one detection method, which is difficult to adapt to the diverse calibration needs of microscales. This article investigates the high-precision measurement method of a microscale based on optoelectronics and the image integration method to solve the diversified calibration needs of microscales. The automatic measurement and processing system integrates two methods: the photoelectric signal measurement method and the photoelectric image measurement method. This article studies the smooth motion method based on ordinary linear guides, investigates the method of reducing the cosine error of a small-range interference length measurement, proposes an image-based line positioning method, and studies the edge and center recognition algorithms of the line. According to the experimental data, the system's measurement accuracy was analyzed using the photoelectric signal measurement method to measure the 1 mm microscale, the maximum difference from the reference value was 0.105 μm, the standard uncertainty was 0.068 μm, and the absolute value of normalized error was less than 1. The accuracy of the image measurement method to measure the 1 mm microscale was consistent with that of the photoelectric signal method. The results show good consistency in the measurement results between the two methods of the integrated measurement system. The photoelectric signal method has the technical characteristics of high measurement efficiency and high accuracy, while the pixel-based measurement of the image method has two-dimensional measurement characteristics, which can realize measurements that cannot be realized by the photoelectric signal method; therefore, the measurement system of optoelectronics and image integration is characterized by high precision and a wide range of measurement adaptations.

Laser in-situ measurement in robotic machining of large-area complex parts

High-precision manufacturing of key components in aerospace plays a crucial role in determining their operational performance, and shape measurement during machining is essential for controlling component accuracy. This article proposes a laser in-situ high-precision measurement method based on improved ICP registration during robotic machining to resolve the contradiction between measurement accuracy and range. Firstly, a robotic in-situ measurement system based on line laser scanning is constructed. Subsequently, the FM-BiKD-ICP algorithm based on geometric feature matching and bi-directional KD-tree proposed in this article is used to complete the high-precision registration of multi-million-scale point cloud data of complex parts with large surface area. Finally, the standard ball target ruler is measured, with the RMSE is under 0.079 mm after multiple registrations, and the average error of hole center distance is less than 0.037 mm on large-area complex parts. These results indicate the high precision of the proposed robot in-situ measurement system.

Improved YOLOv5 Network for High-Precision Three-Dimensional Positioning and Attitude Measurement of Container Spreaders in Automated Quayside Cranes.

For automated quayside container cranes, accurate measurement of the three-dimensional positioning and attitude of the container spreader is crucial for the safe and efficient transfer of containers. This paper proposes a high-precision measurement method for the spreader's three-dimensional position and rotational angles based on a single vertically mounted fixed-focus visual camera. Firstly, an image preprocessing method is proposed for complex port environments. The improved YOLOv5 network, enhanced with an attention mechanism, increases the detection accuracy of the spreader's keypoints and the container lock holes. Combined with image morphological processing methods, the three-dimensional position and rotational angle changes of the spreader are measured. Compared to traditional detection methods, the single-camera-based method for three-dimensional positioning and attitude measurement of the spreader employed in this paper achieves higher detection accuracy for spreader keypoints and lock holes in experiments and improves the operational speed of single operations in actual tests, making it a feasible measurement approach.

Research on High-Precision Measurement Method for Small-Size Gears with Small-Modulus.

Small-modulus gears, which are essential for motion transmission in precision instruments, present a measurement challenge due to their minuscule gear gaps. A high-precision measurement method under the influence of positioning errors is proposed, enabling precise evaluation of the machining quality of small-modulus gears. Firstly, a compound measurement platform for small-modulus gears is developed. Using a 3D model of the measurement system, the mathematical relationships governing motion transmission between various components are analyzed. Secondly, the formation mechanism of gear positioning error is revealed and its important influence on measurement accuracy is discussed. An optimization method for spatial coordinate transformation matrices under positioning errors of gears is proposed. Thirdly, the study focuses on small-sized gears with a modulus of 0.1 mm and a six-level accuracy. Based on the aforementioned measurement system, the tooth profile measurement points are collected in the actual workpiece coordinate system. Then, gear error parameters are extracted based on the established models for tooth profile deviation and pitch deviation. Finally, the accuracy and effectiveness of the proposed measurement method are verified by comparing the measurement results of the P26 gear measuring center.

Major technical barriers and a high-precision distance measurement method for frequency modulated continuous wave LiDAR

Frequency modulated continuous wave (FMCW) light detection and ranging (LiDAR) is considered as one of the most promising 3D imaging technologies by virtue of its single-photon detection sensitivity, high interference immunity, and high precision. In this paper, major technical barriers that limit the precision of FMCW LiDAR range are summarized and analyzed, and solutions to improve the measurement precision are presented. In addition, a novel method for high precision ranging of FMCW LiDAR is proposed, which can be applied to measure target distance in both active and passive environments. The proposed method has a precision of 11 μm in passive environments.

A nN[formula omitted]m level micromotor holding torque measurement method

Efficient and high-precision torque measurement methods for micromotors are globally critical, impeding the advancement of microsystems, particularly ultrasonic micromotors, known for their small size, high speed and high resolution. This paper proposes a novel torque measurement method for ultrasonic micromotors, establishing a torque measurement device that utilizes a parallelogram flexible hinge as the force transmission element. This approach can measure torque at the nano-Newton-meter (nN⋅m) level. The system demonstrates high measurement accuracy, robust anti-interference capability, and a wide measurement range. When the 18 V voltage is applied to the motor, the holding torque is 234.66 nN⋅m, the repeatability error of the system is 1.25%, and the combined standard uncertainty is 5.36 nN⋅m. The proposed method is a pivotal step towards filling the existing technological void, offering a substantial impact on the development of ultrasonic micromotors and the broader field of microsystems.

Improved calibration method based on phase-slope description in phase-shift deflectometry

Phase-shift deflectometry is a widely used high-precision gradient measurement method for assessing the topography of specular objects. The calibration of phase-shift deflectometry measurement systems involves establishing the phase-slope mapping relationship. This paper analyzes the causes of phase variations at different calibration points in existing phase-slope analysis models. Based on the fact that changes in height simultaneously produce phase variations in two perpendicular directions, a decoupling method is proposed to address the phase ambiguity problem to some extent. Through simulation, the variation in height phase and slope distribution were quantitatively analyzed for a unidirectional inclined plane to validate the proposed algorithm. Additionally, measurement experiments were performed on a unidirectional inclined plane with an inclination angle of −2.584° and a concave mirror with a curvature radius of 779.87 mm. Based on the findings, the decoupling method reduced the relative root-mean-square error of the gradient measurement for the inclined plane in the inclined direction by 2.206% and improved the error range of the curvature radius for the concave mirror from [0.55%, 4.1%] to [0.22%, 3.86%]. By comparing with the existed method, the decoupling method showed a certain advantage in practicality.

Research on a Machine Vision-based Blade Measurement Method

A high-precision visual measurement method for the geometric dimensions of oil pump blades is proposed, utilizing an auxiliary measurement mechanism to assist in sub-pixel edge positioning. Based on images of calibration boards, the camera distortion is corrected by partitioning the image into regions and establishing a mapping index between pixel coordinates and real-world coordinates. Under fixed object and image distances, images of the oil pump blades and the contact between the blades and the pump are separately captured. The Canny operator and Sigmoid function are employed to fit the edges, extracting sub-pixel coordinates, which are then mapped to real-world coordinates. Finally, a least squares edge fitting is conducted to compute the dimensional parameters. Experimental results indicate that the use of auxiliary measurement mechanisms effectively enhances the precision of blade measurements, as compared to measurements solely based on oil pump blade images and images of the blade in contact with the pump.

Rapid and high-precision measurement method for fine pitch gears without high-precision installation

To address the measurement issues posed by fine pitch gears, due to the characteristics such as low stiffness and narrow tooth space, this paper proposes a rapid and high-precision measurement method which does not require precise installation by combining optical and visual principles. A calibrated artifact, featuring cylindrical and flat surfaces, was designed to accurately determine the relative positions of the line laser sensor, camera, and rotary table. An experimental setup was constructed, and measurement experiments were conducted on two types of cylindrical gears. To validate the precision of the measurement system, gear profile deviation, helix deviation and pitch deviation were evaluated according to ISO 1328-1:2013. The results were compared with the reference evaluations from Klingelnberg Gear Measuring Center P26, with difference less than 2.4µm. Eight repeatability experiments were conducted, demonstrating that the method proposed satisfies the measurement requirements for fine pitch gears with an accuracy of class 6.

Determination of silicon isotopic composition in soil using gas-source isotope ratio mass spectrometry by thermal decomposition of barium hexafluorosilicate

Determining the Si isotopic compositions of samples of the Earth’s surface is crucial to understanding the implications of the biogeochemistry cycling of Si. This study established an alternative method for high-precision Si isotopic measurement in soil samples using gas-source isotope ratio mass spectrometry, which involved the conversion of Si in the samples into SiF4 gas, which was purified cryogenically and collected for isotopic analysis. The proposed method was applied to determine the Si isotopic composition of two reference materials (GBW04421 and GBW04422), and the results were found to be in good agreement with the certified values. Moreover, the proposed method exhibited a long-term measurement precision of 0.05 ‰–0.08 ‰ (2 s) for the δ30Si values. The δ30Si values obtained from ten soil reference materials ranged from −1.84 ‰ to −0.17 ‰, which were within the range of the values reported in the literature (−1.82 ‰ to −0.15 ‰). The sample preparation and analysis method in this study provided an easy and effective approach to determining the Si isotopic composition of solid samples and offers to the promise of being applicable to biogeochemical analyses of the Earth’s surface processes.