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Latest articles for Measurement Science and Technology

IOPscience

  • A high-precision global unified method based on loop constraints for measurement with 3D scanner
    In the field of 3D object vision measurement, accurately determining the transformation relationship between local and global coordinate systems is crucial. However, existing methods reduce the accuracy of global unification by ignoring global errors among coordinate system transformations. This paper solved this problem by establishing a global measurement system based on optimized coded mark points. Subsequently, a global loop constraint was constructed to calculate the pose of the scanner. Finally, the 3D point cloud of the measured object was unified globally by each pose. The effectiveness of the measuring system and method was evaluated through comprehensive experimentation. The reprojection root-mean-square error (RMSE) with global unified accuracy is less than 0.1 mm, and the RMSE of the measurement for standard ball diameter was 0.074 mm. The experimental results demonstrate that the method exhibits robust unification capabilities in the reconstruction of 3D objects.

  • A fast method for estimating the state of charge and state of health of lithium-ion batteries based on electrochemical impedance spectroscopy at multiple frequency
    Electrochemical impedance spectroscopy (EIS) is widely used for state estimation of energy storage batteries. Currently, EIS is typically obtained via frequency sweep methods using electrochemical workstations, which incur high detection time costs. Existing methods also show limited accuracy in battery state estimation. To reduce measurement time and improve estimation accuracy, a transformer-based estimation method utilizing electrochemical impedance at multiple frequency points is proposed. Specifically, by conducting EIS experiments on 18 650 NCM lithium batteries manufactured by Tianjin Lishen under various states of charge (SOC) (0%–100%), temperatures (15 °C, 25 °C, 35 °C, 45 °C), and aging levels (80%–100%). Characteristic frequencies such as 794.3 Hz, 50.1 Hz, 10 Hz, and 0.158 Hz are selected to reconstruct the full impedance spectrum. Key parameters needed for battery state estimation are identified to enable accurate state assessment of the battery. The results indicate that the reconstruction method proposed in this paper exhibits excellent reproducibility of the original data, and the selected characteristic parameters enable accurate estimation of the battery’s state of health (SOH) and SOC. Compared with the frequency sweep method, the measurement time is reduced by 42%, with maximum estimation errors of 5% for SOH and 3% for SOC. The estimation performance of the proposed method surpasses that of several existing methods.

  • Research on eddy current testing method for titanium alloy bolts based on phase difference
    Aircraft profiled bolts, serving as critical components within the aircraft maneuvering system, are susceptible to fatigue cracks at the root of the threads during operational use, posing significant risks to both human and aircraft safety. In this study, a three-dimensional electromagnetic simulation model of bolts was established to address the challenge of distinguishing defective signals from thread signals during eddy current detection of profiled bolts. The simulation results demonstrated that utilizing a bridge differential probe sliding along the bolt axial direction with coil spacing equal to N times the thread pitch effectively suppressed thread signals, enabling accurate detection of bolt defects. Subsequent investigation revealed a strong resemblance between thread signals and lift-off signals, leading to the proposal of a novel thread noise suppression and defect identification method based on the ‘Thread-Lift-off’ signal equivalent. The method reveals the relationship between the thread signal and the defect signal so that the differential detection coil spacing does not have to be equal to N times the pitch. Subsequently, eddy current detection probes were designed and detection experiments and parameter optimization were carried out. The results show that defects at the root of the thread with a depth of 0.3 mm can be clearly detected by probes with different coil spacing, which verifies the effectiveness and reliability of the detection method.

  • A strategy to fast and precisely estimate IFCB products with a GPS/BDS-2 carrier-range network solution
    Inter-frequency clock bias (IFCB) products are crucial for GPS L1/L5 and BDS-2 B1/B2 precise point positioning with ambiguity resolution (PPP-AR). The computationally efficient epoch-differenced IFCBs are not adequately precise for PPP-AR, while generating precise IFCB products from the undifferenced uncombined network requires several hours. In this study, we proposed a strategy to fast and precisely estimate IFCB products with the carrier-range network solution. The epoch-differenced model was employed to estimate a priori IFCB products, instead of the undifferenced uncombined network solution. Then the IFCBs are re-estimated with carrier ranges, which come from PPP, reducing tens of thousands of ambiguity parameters and speeding up network solutions. GPS and BDS-2 multi-frequency data from 372 stations over 31 d in 2024 were archived for the IFCB estimation and performance evaluation. When 250 stations were used to estimate IFCB products, the processing only took 88 min. Compared with the undifferenced uncombined model, the proposed strategy saved 56.4% of the computational time. The root mean square (RMS) of the differences between estimated IFCBs and the benchmark IFCBs (i.e. GPS L1/L2 and L1/L5 clock offset differences) was 0.07 ns, matching the RMS of IFCBs from undifferenced uncombined network solution. For BDS-2, the RMS difference amounted to 0.02 ns. When these carrier-range IFCBs were used in PPP-AR instead of epoch-differenced IFCBs, the RMS of positioning errors for GPS L1/L5 static PPP-AR solutions improved from 7.0, 5.7, 15.6 mm to 2.7, 2.9, and 8.9 mm in the east, north and up directions, respectively, which is comparable to using IFCBs from undifferenced uncombined network solution. The mean narrow-lane ambiguity fixing rate improved by 20.6% for GPS and 9.9% for BDS-2. Therefore, this strategy enhances efficiency while guaranteeing the precision of the IFCBs, and can offer a rapid and precise IFCB product to support GPS L1/L5 and BDS-2 B1/B2 PPP-AR.

  • Three-dimensional internal deformation measurement methods for hydrogels based on optical coherence tomography
    Depth-resolved, non-contact, full-field three-dimensional (3D) deformation measurement is essential for the application of hydrogels in biomimicry, soft robotics, and optical components. However, current methods are constrained to surface measurements and encounter difficulties in underwater settings. Leveraging the 3D and depth-resolved imaging capabilities of optical coherence tomography (OCT), we propose an OCT-based method for measuring 3D deformation of hydrogels in water. This method integrates underwater electrically driven devices with a Limited-memory Broyden–Fletcher–Goldfarb–Shanno (L-BFGS) based digital volume correlation (DVC) algorithm for 3D strain measurement. We conducted virtual tensile tests and underwater rigid body translation tests to validate the method. The results demonstrated that the strain calculation algorithm had an error of less than 80 μϵ and the system error for underwater strain measurement was less than 800 μϵ. Utilizing this innovative approach, we measured the 3D displacement and strain distributions within carbon nanotube (CNT)/Poly (acrylic acid/acrylamide) (CNT/P(AA/AM)) electro-responsive hydrogel samples. These samples were immersed in solutions of differing ionic concentrations and exposed to a range of direct current electric fields. We discovered that when subjected to electric fields ranging from 1 to 3 volts, the central region of the hydrogel experiences tensile deformation along the direction from electrode to another. However, when the electric field strength is increased to between 4 and 5 volts, the deformation transitions to a compressive state. Additionally, an increase in NaCl concentration results in a decrease in the overall deformation of the hydrogel. In addition, uniaxial tensile tests were carried out on polyvinyl alcohol (PVA) hydrogels underwater to further verify the method. It was demonstrated that the method can accurately capture the internal deformation field of notched PVA hydrogels in solution under uniaxial tension. The integrated OCT-DVC method offers a novel experimental framework for precise 3D deformation measurement and analysis of semi-transparent hydrogel mechanical behavior in liquid environments.