Laser Displacement Transducer Research Articles

Experimental study on monopile-supported offshore wind turbine subjected to long-term wind and wave cyclic loading

Offshore wind energy has recently gained much attention. During its service life, a monopile-supported offshore wind turbine (OWT) is subjected to long-term wind and wave lateral cyclic loads with different cycle characteristics, inducing accumulated deformation of the OWT system to exceed the serviceability limit state and causing safety accidents. In this study, a 1g scaled model test with a similarity ratio of 1:100 was conducted to investigate the lateral response of a monopile-supported OWT in sand under long-term wind and wave cyclic loads. Two sets of centrifugal gear cyclic loading devices applied stable long-term wind and wave cyclic loads and different cyclic load amplitudes and directions were achieved by adjusting the input voltage and counterweight masses. Four groups of long-term cyclic loading tests were conducted for the monopile-supported OWT, considering different wind load simplification methods and various wind-wave load contribution ratios. The lateral displacement and accumulated tilt of the OWT were monitored using two laser displacement transducers installed at different heights. The results show that a simplistic treatment of wind loads as static loads results in an overestimation of the cumulative rotational deformation, and an increase in the wind-wave load contribution ratio decreases the cumulative tilts of the OWT structures.

Characterization of the iPhone LiDAR-Based Sensing System for Vibration Measurement and Modal Analysis.

Portable depth sensing using time-of-flight LiDAR principles is available on iPhone 13 Pro and similar Apple mobile devices. This study sought to characterize the LiDAR sensing system for measuring full-field vibrations to support modal analysis. A vibrating target was employed to identify the limits and quality of the sensor in terms of noise, frequency, and range, and the results were compared to a laser displacement transducer. In addition, properties such as phone-to-target distance and lighting conditions were investigated. It was determined that the optimal phone-to-target distance range is between 0.30 m and 2.00 m. Despite an indicated sampling frequency equal to the 60 Hz framerate of the RGB camera, the LiDAR depth map sampling rate is actually 15 Hz, limiting the utility of this sensor for vibration measurement and presenting challenges if the depth map time series is not downsampled to 15 Hz before further processing. Depth maps were processed with Stochastic Subspace Identification in a Monte Carlo manner for stochastic modal parameter identification of a flexible steel cantilever. Despite significant noise and distortion, the natural frequencies were identified with an average difference of 1.9% in comparison to the laser displacement transducer data, and high-resolution mode shapes including uncertainty ranges were obtained and compared to an analytical solution counterpart. Our findings indicate that mobile LiDAR measurements can be a powerful tool in modal identification if used in combination with prior knowledge of the structural system. The technology has significant potential for applications in structural health monitoring and diagnostics, particularly where non-contact vibration sensing is useful, such as in flexible scaled laboratory models or field scenarios where access to place physical sensors is challenging.

Evaluating die wear-induced edge quality degradation in trimmed DP980 steel sheets from in situ force response monitoring

Assessing trimmed part quality involves periodic examinations of cut edges and shear affected zones to characterize rollover, burnish, fracture and burr formation. Established techniques are thorough and reliable but inherently time consuming. This study correlated die wear-induced force response evolutions and the observed transitions between shear-induced deformation zones for DP980 (C-0.15 wt%Mn-1.5 wt%Si-0.31 wt%) steel sheets subjected to trimming with AISI D2 steel dies. The findings are useful for peripheral assessment of part quality and tool wear via in situ trimming force/displacement response monitoring. Measurements were collected from a load cell and a non-contact laser displacement transducer embedded within the instrumented trimming press. The sliding wear damage and failure processes induced by die–workpiece interactions were correlated to force/displacement response phases. Trimming tests were conducted for 20,000 cycles to observe and assess transformations between rollover and burnish zones with increasing tool wear after the initial contact and at every subsequent 5000 cycle interval. The mean trimming force and maximum die penetration increased, primarily due to die edge blunting, by 1.33 kN (44.3%) and 194 μm (32.2%), respectively. An enlarged die–workpiece contact area increased the resistance force and delayed the onset of fracture with increased sliding damage between sheared surfaces and nearly doubled burnish zone depths. Quantitative attributes of the trimming force/displacement responses were linked to die impact and sliding contact induced damage features of trimmed parts, demonstrating the potential for straightforward, rapid and detailed in-field monitoring of acceptable limits to sheared edge quality.

High-Temperature Effect on the Tensile Mechanical Properties of Unidirectional Carbon Fiber-Reinforced Polymer Plates.

Carbon fiber-reinforced polymer (CFRP) has the advantages of a high strength-weight ratio and excellent fatigue resistance and has been widely used in aerospace, automotive, civil infrastructure, and other fields. The properties of CFRP materials under high temperatures are a key design issue. This paper presents the quasi-static tensile mechanical properties of unidirectional CFRP plates at temperatures ranging from 20 to 600 °C experimentally. The laser displacement transducer was adopted to capture the in situ displacement of the tested specimen. The results showed that the tensile strength of the CFRP specimen was affected by the high-temperature effect significantly, which dropped 68% and 16% for the 200 and 600 °C, respectively, compared with that of the room temperature. The degradation measured by the laser transducer system was more intensive compared with previous studies. The elastic modulus decreased to about 29% of the room temperature value at 200 °C. With the evaporation of the resin, the failure modes of the CFRP experienced brittle fracture to pullout of the fiber tow. The study provides accurate tensile performance of the CFRP plate under high-temperature exposure, which is helpful for the engineering application.

A High-Precision Method for Dynamically Measuring Train Wheel Diameter Using Three Laser Displacement Transducers.

Wheel diameter is a significant geometric parameter related to the safe operation of trains, and needs to be measured dynamically. To the best of the authors’ knowledge, most existing dynamic measurement methods and systems do not meet the requirement that the wheel diameter measurement error for the high-speed vehicle is less than 0.3 mm. In this paper, a simple method for dynamically and precisely measuring train wheel diameter using three one-dimensional laser displacement transducers (1D-LDTs) is proposed for the first time, and a corresponding measurement system which was developed is described. The factors that affect the measurement accuracy were analyzed. As a main factor, rail deformation caused by the wheel-rail interaction force at low (20 km/h) and high (300 km/h) speeds was determined based on the combination of multi-body dynamics and finite element methods, and the effect of rail deformation on measurement accuracy is greatly reduced by a comparative measurement. Field experiments were performed to verify the performance of the developed measurement system, and the results of the repeatability error and measurement error of the system were both less than 0.3 mm, which meets the requirement of wheel diameter measurements for high-speed vehicles.

Site-Response Analysis of Geotextile-Reinforced Toyoura Sand

The response of an equivalent 1 m thick layer of dry, medium dense Toyoura sand reinforced with geotextile fibres was measured in a laminar box under 27 one-dimensional (1D) horizontal harmonic shakings applied to the base of the laminar box. Laser displacement transducers and accelerometers were used to measure the lateral deformation of the box and calculate the shear stress in the soil, respectively. Two distinct site-response analysis techniques were employed to simulate the experiments, including (a) nonlinear analyses and (b) simplified equivalent linear analyses. Differential equations of the site-response analysis are formulated and solved using the finite difference method (FDM). Shear stiffness degradation curves for the reinforced and unreinforced models were indirectly rendered from the laminar box models on the shaking table. These data were fitted with a universal hyperbolic degradation model and integrated into a nonlinear site-response analysis scheme to simulate the horizontal displacement profile of different laminar box models. Results proved that precise estimation could be made as far as there is good knowledge about the shear stiffness modulus degradation model and the level of the shear strain occurred within the soil model. Moreover, Geotextile fibre reinforcement showed both experimentally and analytically to have reduction influences on the horizontal deformation of the reinforced sand models.

Using laser displacement transducer scanning technique in centrifuge modeling of reverse fault–foundation interaction

Reverse fault deformation can cause severe damages of structures built on shallow foundations as observed in previous earthquakes. Centrifuge modeling has been a good approach to investigate the interaction mechanisms of reverse fault and shallow foundation due to the lack of well-documented field data. Displacement measurements of are of critical importance in centrifuge tests for observing responses of soils and shallow foundations. In this paper, Laser Displacement Transducer (LDT) scanning technique was applied to access multi-points (targets) and multi-directions (horizontal, vertical, and rotational) displacement measurements of sand and shallow foundations on ground surface in centrifuge modeling of reverse fault–foundation interaction. Besides, PIV (Particle Image Velocimetry) technique was adopted as well to measure displacements of sand from the front side. The results show that LDT scanning technique has enough accuracy to measure the displacements of sand and foundations on the ground surface. It tackles the limitations of displacement measurements by PIV and LVDT, e.g. underestimated displacements measured by PIV technique due to wall friction, and single point and single direction displacement measurements of LVDTs. The combination of LDT scanning technique and PIV technique is able to obtain more comprehensive displacement information of sand and foundations both at the ground surface and the front side of the soil container.

Novel Laser and Post-Tensioned Wire-Based System for Short-Term and Long-Term Monitoring Deflections in Bridges

The monitoring of static vertical deflections on bridges is still a first-level technological challenge. These data are very useful to understand and to assess the behavior of structural elements in civil engineering, especially for the case of long-term monitoring. The reason is that the material degradation processes and the changes of the mechanical properties of the structure due to aging (because of, for example, creep and shrinkage in concrete and composite bridges) have a direct impact on the exhibited static vertical deflections. This is even a greater challenge in case of high-span high-rise bridges. This paper introduces and evaluates an approach to measure displacements of structures using an original system specially designed to monitor the vertical deflection in high-span high-rise bridges and viaducts, called PTW system. This idea is based on the post-tension technology and its principles, in combination with non-contact laser displacement transducers. In this paper, the conceptual design of the device is described. Additionally, one short-term field testing, carried out to validate the system, is presented and discussed. The results demonstrate that the proposed system is robust, accurate, and reliable, and also inexpensive, which are essential requirements for field implementation.

Video-based multiscale identification approach for tower vibration of a cable-stayed bridge model under earthquake ground motions

A camera can theoretically capture visual information of all target surfaces within its field of view. This capability allows a camera to act as a sensor for determining motion or deformation of targets at appropriate distances. Considering that there are so many cameras in public society (including cameras in smartphones) that can record the vibration of structures in an earthquake, this capability will be very helpful for assessing structural seismic damage post-earthquake. To this end, this paper proposes a two-step combination of the SCF (support correlation filters) algorithm with the KLT (Kanade-Lucas-Tomasi) algorithm for displacement identification of cable-stayed bridges from video with higher accuracy over SCF only and higher robustness over KLT only. The SCF algorithm can robustly and quickly track the target in the video, and the KLT algorithm can accurately track the pixel locations of targets. The shaking table test of a scale cable-stayed bridge model was conducted, and the vibration of the tower was recorded by a camera. The linear and nonlinear displacement responses of the tower under different earthquake ground motions were identified. The accuracy of the identified displacement response was validated through comparison with measurements from laser displacement transducers.

Dynamic Responses of a Four-Span Continuous Plate Structure Subjected to Moving Cars With Time-Varying Speeds

This paper presents an experimental and theoretical study of vibration of a four-span continuous plate with two rails on top and four extra supports excited by one or two moving model cars, which is meant to represent vehicle–track–bridge dynamic interaction. Measured natural frequencies of the plate structure are used to update the finite element (FE) model of the structure. Four laser displacement transducers are placed on the ground to measure the displacements of the plate. A laser-Doppler vibrometer is used to measure the real-time speed of the moving cars, which reveals that the speeds decrease with time at a small and almost constant deceleration which can affect the structural dynamic response. A fascinating experiment is the use of two cars connected in series, which is very rare and has never been done on a multispan structure. Vibration of the plate structure excited by two moving cars separated at a distance is also measured and exhibits interesting dynamic behavior too. A theoretical model of the whole structure is constructed and an iterative method is developed to determine the dynamic response. The numerical and the experimental results are found to agree very well, in particular when deceleration is considered in the theoretical model.

A Novel Laser and Video-Based Displacement Transducer to Monitor Bridge Deflections.

The measurement of static vertical deflections on bridges continues to be a first-level technological challenge. These data are of great interest, especially for the case of long-term bridge monitoring; in fact, they are perhaps more valuable than any other measurable parameter. This is because material degradation processes and changes of the mechanical properties of the structure due to aging (for example creep and shrinkage in concrete bridges) have a direct impact on the exhibited static vertical deflections. This paper introduces and evaluates an approach to monitor displacements and rotations of structures using a novel laser and video-based displacement transducer (LVBDT). The proposed system combines the use of laser beams, LED lights, and a digital video camera, and was especially designed to capture static and slow-varying displacements. Contrary to other video-based approaches, the camera is located on the bridge, hence allowing to capture displacements at one location. Subsequently, the sensing approach and the procedure to estimate displacements and the rotations are described. Additionally, laboratory and in-service field testing carried out to validate the system are presented and discussed. The results demonstrate that the proposed sensing approach is robust, accurate, and reliable, and also inexpensive, which are essential for field implementation.

Experimental investigation of local-flexural interactive buckling of cold-formed steel channel columns

This paper presents the results of a comprehensive experimental programme aimed at studying the interaction of local and overall flexural buckling in cold-formed steel (CFS) plain and lipped channels under axial compression. The results were further used to verify the accuracy of the current design procedures in Eurocode 3, as well as to evaluate the effectiveness of a previously proposed optimisation methodology. A total of 36 axial compression tests on CFS channels with three different lengths (1 m, 1.5 m and 2 m) and four different cross-sections were conducted under a concentrically applied load and pin-ended boundary conditions. The initial geometric imperfections of the specimens were measured using a specially designed set-up with laser displacement transducers. Material tests were also carried out to determine the tensile properties of the flat parts of the cross-sections, as well as the cold-worked corner regions. A comparison between the experimental results and the Eurocode 3 predictions showed that the effective width approach combined with the P–M interaction equation proposed in Eurocode 3 to take into account the shift of the effective centroid consistently provided safe results. However, the Eurocode 3 procedures were also quite conservative in predicting the capacity pertaining to local-global interaction buckling, especially for plain channels. Furthermore, the experimental data confirmed the results of an optimisation study and demonstrated that the optimised CFS columns exhibited a capacity which was up to 26% higher than the standard channel with the same amount of material taken as a starting point.

Local-flexural interactive buckling of standard and optimised cold-formed steel columns

This paper aims to study the interaction of local and overall flexural buckling in cold-formed steel (CFS) channels under axial compression. Detailed nonlinear FE models were developed and validated against a total of 36 axial compression tests on CFS plain and lipped channel columns with pin-ended boundary conditions. The numerical models incorporated the non-linear stress-strain behaviour of CFS material and enhanced properties of cold-worked corner regions obtained from coupon tests. The effects of initial geometric imperfections of the specimens measured by a specially designed set-up with laser displacement transducers were also taken into account. The developed FE models produced excellent predictions of the ultimate strength of the specimens obtained from experimental tests. The validated FE models and experimental results were then used to assess the adequacy of the effective width method in Eurocode 3 (EC3) and Direct Strength Method (DSM) in estimating the design capacity of a wide range of conventional and optimised design CFS channel column sections. The results indicate that Eurocode 3 provides conservative predictions (on average 21% deviation) for the compressive capacity of plain and lipped channel sections, while in general DSM predictions are more accurate for lipped channels. A comparison between FE predictions and tested results show that geometric imperfections can change the FE predictions by up to 20% and 40%, respectively, for lipped and plain channel columns, while the strain hardening effect at the rounded corner regions of the cross-sections is negligible. The results also confirmed that the proposed numerical model is able to provide a consistent and reliable prediction on the efficiency of a previously proposed optimisation methodology.

Mechanical Strength Evaluation of YSZ, GDC and LSCF under SOFC Operating Conditions

1. Introduction For designing SOFC with high mechanical reliability, it is necessary to analyze stress state of cells and stacks under various operating conditions. Based on this concept, our group has attempted to construct multiscale model which can simulate elastic and inelastic deformation and fracture probability with consideration of electro-chemical, thermal and mechanical properties of constituent materials. In this study, we focus on strength of SOFC materials including 8YSZ electrolyte, 10GDC barrier layer and LSCF6428 cathode which are well-known as brittle materials. Their elastic properties and fracture strengths are evaluated as a function of temperature. 2. Experiments Evaluation of elastic and fracture properties Mechanical strength evaluation is performed by Small Punch (SP) tests. The tests were performed on a universal testing machine (INSTRON 5565). The circular specimens were simply supported at the circumferential edge of an alumina tube and subjected to a concentrated load at their center position. The load was applied through a puncher at a crosshead speed of 0.05 mm/min until a final failure occurred. The load-line deflection of the specimens was measured by monitoring the movement of an Al2O3 rod of which one end is made in contact with the bottom surface of the sample, and the position of the other end is monitored using a laser displacement transducer. The elastic modulus ESP and fracture stress σf_SP were calculated using the following equations : ESP = f(t/a)[3a 2(1-ν)(3+ν)P/4πδt 3], σ f_SP =Pmax (1+ν)[0.485ln(a/t)+0.52+3/2π(1+ν)]/t 2, where Pmax is the load applied by the puncher, δ is the load-line deflection, t is the thickness of the specimen,n is Poisson’s ratio, a is the radius of the load support, and f(t/a) is a correction factor of the specimen thickness for the thin plate theory given by the following equation: f(t/a)=1.5136(t/a)2+0.0162(t/a)+0.9962. The elastic modulus ESP was computed from the linear slope of the load versus load-line deflection records (P/δ), and the fracture stress σf_SP was calculated from the peak load Pmax . Sample preparation Commercial powders of 10 mol% gadolinia doped ceria (10GDC) was obtained from Shin-Etsu Chemical Co., Ltd.(Tokyo, Japan) and La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF6428) from Noritake Co.,Ltd.(Nagoya, Japan). The 10GDC and LSCF6428 powders were uniaxially pressed to f10mm disc-shape with pressure 100 MPa and then with a cold isostatic press (CIP) at 170 MPa. After that, 10GDC green samples were sintered at 1550˚C for 6 hours with 5˚C/min heating rate and 2˚C/min cooling rate. LSCF6428 green samples were sintered at 1300˚C for 6 hours with the same heating and cooling rates. As a SP test specimen, sintered discs were polished to a uniform thickness about 0.5mm by mechanical polishing. One side of the pellet was mirror-polished with a diamond paste of 3mm. 8 mol % Y2O3stabilized zirconia (8YSZ) plates of 7×7×0.5 mm with one side polished were supplied by Japan Fine Ceramic Co., Ltd (Sendai, Japan). We performed ten experiments for respective materials at selected temperature between R.T. and 800˚C in air. Average and standard deviation of elastic moduli and scale and shape parameters of fracture stress based on Weibull distribution were calculated from experimental results at each temperature. Scale parameter means fracture stress at fracture probability 63.2% and, shape parameter indicates the degree of dispersion of fracture stress on Weibull distribution. Lager shape parameter means the dispersion of fracture stress is smaller, and the strength stability is higher. 3. Result and discussion The temperature dependences of elastic moduli and scale and shape parameters of 8YSZ, 10GDC and LSCF6428 are shown in Fig.1 (a), (b). For 8YSZ, elasticity, scale and shape parameters showed minimum at 400˚C. It means decrease of elasticity and fracture stress of 8YSZ is accompanied by increase in the dispersion of fracture stress. For 10GDC, both elasticity and scale parameter decreased up to 200˚C, and gradually increased with further increase in temperature. It should be noted that shape parameter increased with temperature increasing. It shows that the strength stability increased with temperature. For LSCF6428, elasticity once dropped between 200˚C and 400˚C, increased with further heating up to 800˚C. Scale parameter tendency is similar to 10 GDC, but the strength stability of both is switched at 600˚C. In this way, the quantitative characterization of the strength stability in 8YSZ, 10GDC and LSCF6428 are evaluated with their fracture stress and elasticity. Figure 1

Experimental modal analysis of straight and curved slender beams by piezoelectric transducers

We present the use of piezoelectric disk buzzers, usual in stringed musical instruments to acquire sound as a voltage signal, for experimental modal analysis. These transducers helped in extracting natural frequencies and mode shapes of an aluminium beam and a steel arch in the laboratory. The results are compared with theoretical predictions and experimental values obtained by accelerometers and a laser displacement transducer. High accuracy, small dimensions, low weight, easy usage, and low cost, make piezoelectric pickups an attractive tool for the experimental modal analysis of engineering structures.

Experimental study of blast mitigation by foamed concrete

Field blast tests were performed to investigate the effects of foamed concrete panels on structural response. Foamed concrete specimen with two densities and aluminum-alloy front face sheet were studied. Effects of four key parameters, that is, blast impulse, foamed concrete density, thickness of foamed concrete panel, and the thickness of front face sheet, on structural response were studied using ballistic pendulum system and laser displacement transducer. Deformation of the back panel protected by foamed concrete and the failure modes of foamed concrete specimen when subjected to blast load were obtained. Experimental results indicate that foamed concrete can be used to attenuate blast load and reduce structural deformation effectively.

Partial-profilogram reconstruction method to measure the geometric parameters of wheels in dynamic condition

ABSTRACTThe present work poses a method for the measurement of geometric parameters of rail wheels in a dynamic condition, by reconstructing the profilogram from a portion of the wheel surface wear with artificial vision. The suggested procedure can work with a two-dimensional laser displacement transducer or by processing a sole image from a single camera with a structured light source. These two procedures require fewer devices and simpler implementation processes and allow the use of mathematical algorithms that demand less information processing, thus generating more accurate results. Railway operators may implement this method to perform predictive maintenance to their rolling stock at a fraction of the regular cost; thus achieving better precision, availability, maintenance performance and improving safety. Results were compared to those given by commercial equipment, showing similar precision but a better cost–benefit relation.

Multi-type sensor placement and response reconstruction for structural health monitoring of long-span suspension bridges

This study is devoted to the experimental validation of the multi-type sensor placement and response reconstruction method for structural health monitoring of long-span suspension bridges. The method for multi-type sensor placement and response reconstruction is briefly described. A test bed, comprising of a physical model and an updated finite element (FE) model of a long-span suspension bridge is also concisely introduced. The proposed method is then applied to the test bed; the equation of motion of the test bed subject to ground motion, the objective function for sensor location optimization, the principles for mode selection and multi-type response reconstruction are established. A numerical study using the updated FE model is performed to select the sensor types, numbers, and locations. Subsequently, with the identified sensor locations and some practical considerations, fiber Bragg grating (FBG) sensors, laser displacement transducers, and accelerometers are installed on the physical bridge model. Finally, experimental investigations are conducted to validate the proposed method. The experimental results show that the reconstructed responses using the measured responses from the limited number of multi-type sensors agree well with the actual bridge responses. The proposed method is validated to be feasible and effective for the monitoring of structural behavior of long-span suspension bridges.

Investigation of the evolutionary process of a reinforced model slope using a fiber-optic monitoring network

The stability condition of a reinforced slope is influenced by many factors, such as surface loading, adjacent excavation, groundwater seepage, rainfall infiltration, and earthquake. In order to investigate the evolution of stability condition of a soil slope reinforced with soil nails, a physical model test at 1g condition was conducted in the laboratory. In the model test, an innovative quasi-distributed fiber-optic sensing network based on the fiber Bragg grating (FBG) technology was developed to monitor the strain distributions of the soil nails, the slope subsurface displacements, and the internal strains of the soil mass, together with laser displacement transducers for surface displacement measurement. The sensor installation and temperature compensation methods of the monitoring system were presented in detail. During testing, the surcharge loading was applied on the slope crest in stages using hydraulic jacks and the slope behavior was carefully monitored. The simplified Bishop's method was performed beforehand to obtain the factors of safety and the critical slip surfaces of the model slope. It is found that the measured strains of the model soil nails had a close relationship with loading magnitudes. The bending stiffness of the model soil nails contributed to the stability of the model slope when considerably large deformation occurred. The variation of slope movements and the distribution pattern of internal strains in the active and passive zones were further discussed, which indicates the progressive evolutionary process of the reinforced slope. It is verified that the fiber-optic monitoring data can identify the evolutionary stages of a reinforced slope effectively.

A simple method for dynamically measuring the diameters of train wheels using a one-dimensional laser displacement transducer

A simple method for dynamically measuring the diameters of train wheels that uses a relative measurement system is proposed. Only a laser displacement transducer and eddy current sensors are used to dynamically measure the wheel diameter when a train passes through the measurement device, and a simple equation for computing the diameter is given. The main factors influencing the measurement uncertainty were analyzed and simulated, and the effect of vibration on the diameter measurement was also analyzed using a simulation based on the finite element method. The measurement error of a laser displacement transducer, the position error and vibration are the primary factors that influence the accuracy of the diameter measurement, and of these factors, the influence of vibration can be reduced by comparative measurement. To further decrease the influence of wheel position error on the accuracy of the diameter measurement, two eddy current sensors were used instead of only one eddy current sensor, and the simulation results indicated that the influence of wheel position error on the accuracy of the diameter measurement can be greatly reduced. The theoretical analysis indicated that the measurement device has a measurement uncertainty of ±0.37mm, which agrees with the site experimental results, and the measurement system can satisfy the requirements of dynamically measuring the train diameters in situ.