Dynamic Measurement Method Research Articles

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%.

Dynamic Stress Measurement Method in Concrete Based on Matching Error Analysis and Correction

Dynamic Stress Measurement Method in Concrete Based on Matching Error Analysis and Correction

Nonlinear, elastic, piezoelectric, electrostrictive, and dielectric constants of lithium tantalate

Three third-order dielectric constants, 8 electrostrictive constants, 13 third-order piezoelectric constants, and 14 third-order elastic constants for lithium tantalate (LiTaO3) single crystals, which are mainly used in surface acoustic wave (SAW) devices, were determined as part of basic research to realize SAW devices with a low degree of nonlinearity. The third-order dielectric constants were determined by measuring the change in capacitance along selected directions when an alternating electric field was applied to the crystal. The electrostrictive constants were determined by measuring the change in capacitance when static stress was applied. Some of the piezoelectric constants were determined directly from the change in sound velocity due to the application of an alternating electric field, whereas others were obtained from the measured dielectric constants, electrostrictive constants, and the change in sound velocity due to an alternating electric field. In addition, the elastic constants (compliance) were determined using the three aforementioned determined nonlinear constants and the measured small-amplitude ultrasonic velocity change as a function of applied static stress. The measurements performed in the present study are more advanced than those reported for LiNbO3 single crystals in 1987 due to the adoption of the d-form nonlinear piezoelectric equation (instead of the e-form) and a higher degree of precision using dynamic measurement methods. The use of the d-form of the nonlinear piezoelectric equation allows many nonlinear constants to be determined independently from other nonlinear constants, eliminating measurement errors associated with these other constants. The d-form nonlinear constants obtained in the present study were converted to e-form constants to make them applicable to the analysis of nonlinear phenomena in piezoelectric devices.

Quantitative analysis of the density of states distribution in N-type polymer filed-effect transistor

In the advancement of polymer field-effect transistors, both p-type and n-type polymer transistors are indispensable because they are the basic components of complementary metal oxide semiconductor (CMOS) logic circuitry. The scarcity of research on the interface properties of n-type polymer transistors, particularly regarding their density of state (DOS) distribution hinders the device modeling and further optimization of n-type polymer transistor. Consequently, the focus on understanding and investigating n-type polymer transistors interface properties holds substantial value and relevance, as it fills a critical knowledge gap in the polymer transistors. In view of this, an n-type poly((N,N0-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl)-alt-5,50-(2,29-bisthiophene)) (N2200) polymer transistor was fabricated and a dynamic quantitative measurement method was utilized to investigate the DOS distribution of polymer transistors. Comparative analyses were conducted on the drain current (ID), carrier charge (Q), and DOS with varying pulse fall times (Tf). Variations in pulse fall times revealed significant differences in the DOS near the edge of the lowest unoccupied molecular orbital (LUMO), with a maximum DOS of 8 × 1013 cm−2 eV−1 observed at Tf = 1000 μs and a maximum of 2 × 1013 cm−2 eV−1 at Tf = 100 μs. By using different Tf, an effective method was successfully utilized for analyzing the effects of water and oxygen molecules on the DOS distribution of n-type polymer transistors.

Dynamic Measurement Method for Steering Wheel Angle of Autonomous Agricultural Vehicles

Steering wheel angle is an important and essential parameter of the navigation control of autonomous wheeled vehicles. At present, the combination of rotary angle sensors and four-link mechanisms is the main sensing approach for steering wheel angle with high measurement accuracy, which is widely adopted in autonomous agriculture vehicles. However, in a complex and challenging farmland environment, there are a series of prominent problems such as complicated installation and debugging, spattered mud blocking the parallel four-bar mechanism, breakage of the sensor wire during operation, and separate calibrations for different vehicles. To avoid the above problems, a novel dynamic measurement method for steering wheel angle is presented based on vehicle attitude information and a non-contact attitude sensor. First, the working principle of the proposed measurement method and the effect of zero position error on measurement accuracy and path tracking are analyzed. Then, an optimization algorithm for zero position error of steering wheel angle is proposed. The experimental platform is assembled based on a 2ZG-6DM rice transplanter by software design and hardware modification. Finally, comparative tests are conducted to demonstrate the effectiveness and priority of the proposed dynamic sensing method. Experimental results show that the average absolute error of the straight path is 0.057° and the corresponding standard deviation of the error is 0.483°. The average absolute error of the turning path is 0.686° and the standard deviation of the error is 0.931°. This implies the proposed dynamic sensing method can accurately realize the collection of the steering wheel angle. Compared to the traditional measurement method, the proposed dynamic sensing method greatly improves the measurement reliability of the steering wheel angle and avoids complicated installation and debugging of different vehicles. The separate calibrations for different vehicles are not needed since the proposed measurement method is not dependent on the kinematic models of the vehicles. Given that the attitude sensor can be installed at a higher position on the wheel, sensor damage from mud blocking and the sensor wire breaking is also avoided.

Dynamic Attitude Inertial Measurement Method for Typical Regions of Deck Deformation

Due to the deformation of ships, it becomes difficult to ensure the accuracy of attitude measurement in typical areas on the deck, which seriously impacts the safety and operational efficiency of shipborne equipment. To address this issue, this paper presents a parameter identification method for dynamic deformation models based on angle increment differences and introduces the related vector machine (RVM) algorithm for online estimation of dynamic deformation model parameters. In view of the truncation error and non-Gaussian noise of the model, this article proposes a dynamic attitude measurement method based on model predictive filtering (MPF), constructs a dynamic measurement model using Rodrigues parameters in an inertial frame, and designs a maximum correlation entropy (MCE) robust filter to achieve robust estimation of deck dynamic deformation. The performance of the method is verified through simulation analysis and shipborne experiments. The comparative results indicate that, compared with existing methods, the proposed improved deck dynamic attitude measurement algorithm based on model prediction (IDAM) can substantially enhance the accuracy of attitude measurement in the presence of deck dynamic deformations.

A prediction model of gear radial composite deviation based on digital twin mesh

The intelligent development of traditional detection technology through the application of emerging technologies is a crucial trend in achieving multi-information gear detection. In this paper, digital twin mesh (DTM) is proposed, and according to the proposed DTM, the prediction model (DTM model) of gear radial composite deviation is established. The DTM model is established by merging the mechanism and the data model with a parallel structure. The mechanism model is established based on the measurement principle. The data model is established through the Gaussian process regression algorithm. Comparing the predicted results of DTM model with the measured results, it is observed that the DTM model demonstrates superior precision. The DTM model achieves a prediction accuracy exceeding 87 % for total radial composite deviation and exceeding 90 % for tooth-to-tooth radial composite deviation. This DTM model holds significant engineering application value and offers insights for the non-contact dynamic measurement method of gears.

M13 bacteriophage-based high-sensitivity Fabry-Pérot etalon for detecting humidity and volatile organic compounds

Various sensor applications have been developed for protection against hazardous environments, and research on functional materials to enhance performance has also been pursued. The M13 bacteriophage (M13) has found utility in sensor applications like disease diagnosis and detection of harmful substances due to its potential for controlling interaction with target substances through adjustments in electrochemical and mechanical properties via genetic engineering technology. However, while optimizing reactivity or binding affinity between M13 and target materials is crucial for sensor performance enhancement, precise dynamic measurement methods for this were lacking. This study demonstrates the application of an M13-based dynamic actuator in a Fabry–Pérot etalon (M13-FPE) as a spacer for precise measurement of humidity and reactivity to volatile organic compounds (VOCs). The transmission spectrum is optimized by adjusting the reflectance and cavity gap size (dM13) of the two mirrors comprising the M13-FPE, and changes are measured in a rainbow-color-dotted (RCD) pattern using a customized spectrometer. Utilizing the peak wavelengths of the RCD pattern, the change in dM13 is dynamically and precisely measured, revealing approximately 3% and 0.3% swelling for ethanol and isopropyl alcohol, respectively. M13 demonstrates binding affinities of 827 ppb and 158 ppb for ethanol and isopropyl alcohol, respectively, with its low reactivity measured precisely, exhibiting an error of 0.03 nm using the peak wavelength change rate.

A dynamic turbine tip clearance measurement method based on laser self-mixing interferometric ranging considering Doppler effect

A dynamic turbine tip clearance measurement method based on laser self-mixing interferometric ranging considering Doppler effect

Direct measurement for hand-transmitted vibration of human fingers-hand-arm system in the zero-gravity environment

This paper proposes a direct measurement method to obtain the mechanical impedance and vibration transmissibility of the fingers-hand-arm system when operating power tools based on zero-gravity environment simulations. A hand-transmitted vibration measurement system with a suspension device for zero-gravity simulation is first built. The two-step dynamic measurement method is used to measure the dynamic force and acceleration of fingers and palm directly. The forearm and upper arm’s acceleration is also measured using the two-step dynamic measurement method. Based on eliminating the effect of the handle’s effective mass on the mechanical impedance, the mechanical impedance and vibration transmissibility of the human fingers-hand-arm system during the actual operation of the power tool are calculated by using the measured data, and the biodynamic response characteristics of the fingers-hand-arm system at different frequencies are analyzed. The results show that, under the condition of the ISO standardized operating posture (ISO 10819, 2013), the mechanical impedance and vibration transmissibility curves obtained by direct measurement of 21 subjects have remarkable consistency respectively. Compared with the experimental data in the gravity environment, the mechanical impedance and the vibration transmissibility obtained based on the zero-gravity simulation are more consistent with the working conditions of the on-orbit maintenance power tools.

On-site dynamic deformation measurements based on enhanced temporal speckle pattern interferometry

This paper proposes a dynamic deformation measurement method based on temporal speckle pattern interferometry, tailored for on-site applications. This technique utilizes an improved dynamic phase extraction algorithm to obtain phases associated with both ground vibrations and object deformations. Deformations are discerned from vibrations by employing a synchronized measurement system that integrates laser Doppler vibrometers and a high-speed camera. The effectiveness of the method for dynamic deformation measurements under micron-level vibrations is verified by experiments.

Error correction method based on dual-beam laser for curved rail profile measurement

The current method of dynamic rail profile measurement involves the installation of a line-structured light sensor at the base of the train. The accuracy of this measurement is influenced by the vertical relationship between the laser plane of the light sensor and the longitudinal direction of the rail (LDR). When a train travels in a straight line, the normal of the laser plane aligns with the LDR. However, when the train curves, the angle at which its wheels connect with the rails causes the laser plane’s normal direction to deviate from the LDR, leading to measurement errors. To address this issue, we propose a method for curved rail profile measurement using a dual-beam laser to correct these errors. This method involves generating an auxiliary 3D rail reflecting the LDR and a virtual 3D rail reflecting the normal direction of the laser plane from the cross-section image of the dual-beam laser. An optimization function is then formulated to determine the optimal auxiliary plane (optimal-AP) by analyzing the alignment or intersection between the auxiliary and virtual 3D rails. Distorted contour points are projected onto the optimal-AP to rectify errors. Experiments validate the accuracy and effectiveness of this proposed method. The results show that, regardless of pitch or yaw movement between the laser plane and the LDR, the error in measuring corrected profile wear remains consistently below 0.10 millimeters, thereby meeting the accuracy standard for rail wear measurement. This approach rectifies measurement errors in curved rail profiles from a 3D perspective, ensuring accurate measurements even under complex working conditions. It also provides a valuable reference for error analysis and improving dynamic rail profile measurement accuracy.

Dynamic accuracy measurement method for star trackers using a time-synchronized high-accuracy turntable

Star trackers are typically used in a spacecraft to provide absolute attitude information to the on-board attitude control system so as to promote high accuracy. The performance of the star tracker is rather important. Attitude incorrectness provided by star trackers may lead to bad navigation with big deviations, even failure of satellites. Therefore, how to realize and verify the accuracy is crucial. As a matter of fact, it is difficult to validate accuracy of star trackers on the ground, especially for star trackers under highly dynamic conditions. In this paper, an accuracy measurement method for star trackers under dynamic conditions is proposed, utilizing a high-accuracy swing table to provide reference to compare. To this end, a swing table, star tracker, and the test equipment are synchronized, in order to reduce systematic errors. As the motion trajectory of the swing table can be set beforehand, the initial attitude of the star tracker can be predicted through a set of coordinate transformations. As a result, the star tracker is able to keep tracking, regardless of the angular velocity of the swing table. This makes the statistical sample points more sufficient and the results more reliable. Moreover, it can evaluate the angular velocity of star trackers up to 20°/s. In comparison with the conventional method with simulated stars, this method utilizes real navigation stars as observation targets making the measurement results much closer to the on-orbit performance. Lastly, but much more importantly, it can also verify the performance of a star tracker in one experiment, such as sensitivity, static performance, capture probability, and so on. Experimental results demonstrate that the proposed method is effective, especially for highly dynamic star trackers. Such a measurement environment is close to the in-orbit conditions, and it can satisfy the stringent requirement for star trackers under high dynamics.

Research on dynamic measurement method of speckle in laser display

Research on dynamic measurement method of speckle in laser display

Dynamic transient response measurement method for parity-time-symmetric LC telemetry sensors

Parity-time symmetry concept has been utilized to develop high precision LC passive wireless sensors. However, they often use the traditional frequency sweeping method for measurements, thus the measurement precision and speed are strongly influenced by the performance of the frequency domain analysis instrument. To solve this issue, herein we proposed a time domain measurement method and extracted sensing information from the transient response signals of the reader. Its measurement speed was much faster than that using the frequency domain analysis instrument. A distance sensing system was developed to demonstrate the feasibility of the new method. It showed a resolution of less than 300 nm for detections of centimeter range, and the measurement time was as short as 100 μs, which was at least 1000 times faster than that using the traditional method. This technology can be explored as an innovative strategy for LC passive telemetry sensing.

Research on the calculation and evaluation method of transmission efficiency of noncircular planetary gear

The torque fluctuation characteristics of noncircular planetary gear (NPG) systems are difficult to obtain, and there is no clear analysis method and evaluation method for transmission efficiency, which seriously affects their service performance. Given that, this article establishes a torque fluctuation model for NPG systems based on the principle of gear meshing and differential geometry theory and methods, taking into account factors such as actual working conditions and speed loads. And proposed, the comprehensive transmission rate, a new method for evaluating the efficiency of NPG systems. By analyzing the actual working conditions of NPG systems, the influence mechanism of alternating load and speed on torque fluctuation and transmission efficiency was explored. The research results indicate that the alternating load can cause an increase in system impact and vibration. The comprehensive transmission rate of NPG systems decreases with increasing rotational speed and increases with increasing load, and is more sensitive to changes in rotational speed. The trend of comprehensive transmission rate and transmission efficiency of NPG systems is basically consistent, indicating that the proposed method of using comprehensive transmission rate to evaluate transmission efficiency is a practical and feasible analysis method. The research results can provide a new method for dynamic measurement and evaluation of torque and transmission efficiency of non-circular gear transmission systems.

A novel impact indentation technique with dynamic calibration method for measurement of dynamic mechanical properties

High strain rates and continuous real-time data acquisition are difficult to balance in existing impact indentation techniques. Meanwhile, the inaccuracy of the testing P-h curves limits the development of quantitative applications for dynamic testing of mechanical properties at micro region. This article develops a momentum exchange impact indentation testing method, which extends the testing range of strain rate to above 105 s−1, and at the same time avoids secondary impact. Impact indentation tests are conducted on single-crystal aluminum specimens with impact velocity from 76.9 to 176 mm/s. Based on calibrated data, the comparison of calculation methods for dynamic hardness is carried out. The dynamic elastic modulus is obtained by means of the Oliver-Pharr method, which increases from 71.9 to 89.4 GPa with increasing impact velocity. A multi-dimensional data analysis method is proposed based on the obtained experimental data to quantitatively study the damping and stiffness characteristics of materials. This testing method is particularly useful for quantitatively obtaining the micro region dynamic mechanical properties of solid materials at high strain rates.

Research on Full-Field Dynamic Deflection Measurement of Beams Based on Dense Feature Matching and Mismatch Removal Method

To solve the problems of measurement errors led by mismatches of dense feature matching in machine vision structural deflection measurement, this paper proposes a dense feature extraction, matching, and dual-step mismatch-removal-based full-field structural dynamic deflection measurement method. First, the of dense feature detection and matching theory is introduced to extract the SIFT feature points on a structural surface in an image sequence and matched by FLANN to trace the structure movement, and the mechanisms and causes of mismatches are analyzed. Then, a dual-step mismatch removal method combining RANSAC and Structural Displacement Continuity Restriction (SDCR) is introduced to achieve full-field dynamic beam deflection measurement. The proposed method is validated through indoor cantilever beam experiments, and results show that the method can effectively eliminate a large number of SIFT feature mismatches (accounting for approximately 55% of the total matched feature points). The full-field dynamic displacement field of the beam can be measured with the correctly matched dense feature points by converting dense feature point displacements into continuous and uniform spatiotemporal deflections of the structure. A comparison with the GOM Correlate Professional DIC measurement system was conducted, and the maximum measurement error of the cantilever beam dynamic displacement of the proposed method is between 0.024 and 0.053 mm, the root mean squared error of displacement is approximately 0.01 mm, and the correlation coefficient between two deflection–time curves reaches 0.9964. The proposed algorithm is proven to be effective in full-field displacement measurement and has great potential in future structural health monitoring of bridges.

Self-Regulating Dynamic Measurement Method

Self-Regulating Dynamic Measurement Method

Self-Regulating Dynamic Measurement Method

A dynamic measuring system is considered. A new model of the measuring system, a method for processing of measurement results and a method of restoring the input signal of the system by the noisy output signal are proposed. The estimation of the accuracy of the method and a computational experiment demonstrating the efficiency of the signal recovery method are presented.