Coordinate Measurement Method Research Articles

Exploring the relationship between pavement mean texture depth and mean profile depth: from theoretical derivation to field results

Pavement mean texture depth (MTD) and mean profile depth (MPD) are common evaluation indicators for characterizing the pavement surface. Clarifying the relationship between the two contributes to coordinate various measurement methods and evaluation criterions. The calculation methods of MTD and MPD were first introduced to trace the similarity between the indicators. Subsequently, the tortuosity area of surface texture was observed using x-ray Computer Tomography (CT). To further determine the model parameter, over 3000 sets of field data in Research Institute of Highway Ministry of Transport (RIOH) track were measured. Meanwhile, the field results of another track and existing recommended model were also used to validate the model. The results show that the shift relationship between MTD and MPD is theoretically unified into a linear model with a slope of 1 and an intercept related to the surface tortuosity. These tortuous areas, the main difference source between the two indicators, would lead to a greater equivalent texture depth under the coarser gradation or lower the compactness of the asphalt mixture. Even for the different track roads, the determined model (MTD = MPD + 0.03) has a lower mean relative estimation error, indicating good applicability. This study provides theoretical explanation and empirical references for the automated laser-based texture detection.

Comparison of two options for building three-coordinate electronic intelligence stations

The subject–coordinate measurement methods in ground electronic intelligence (ELINT) stations. The goal is to conduct a comparative analysis of two options for the composition ground ELINT stations in terms of accuracy of measuring coordinate information. The tasks to be solved are as follows: assessing the accuracy of determining the coordinates of the time difference of arrival method (TDOAМ) and hybrid method (HM); obtaining analytical ratios for estimating the root-mean-square error (RMSE) of the accuracy of measuring the altitude of radio emission sources (RES) of these methods; on the basis of the obtained estimates and analytical ratios, a comparative analysis of the methods, under conditions where the accuracy of the coordinate information obtained by both methods is commensurate; and development of recommendations regarding the practical application of HM coordinate measurements. The methods used are: the theory of measurements and the theory of evaluation of coordinate information. The following results were obtained: a comparative analysis of the TDOAМ and HM was performed according to the RMSE of the determination of plane coordinates and the altitude of the RES. The accuracy assessment was performed in a known way, based on the linearization of the functional dependence between the measured primary parameters (range differences, elevation angle) and spatial coordinates by expanding in a Taylor series with the deduction of the first two terms of the series. Calculations have shown that the presence of the third side station has very little effect on the accuracy of determining plane coordinates. Significant differences appear only in the results of estimating the RMSE of the RES altitude. To compare the methods, analytical relationships were obtained for estimating the RMSE of the altitude measurement. The condition is determined under which the accuracy of determining the altitude for the HM is not worse than that for the TDOAМ (the accuracy is the same). Starting from this value and further, when using the HM, the altitude is determined more accurately. Conclusions. An HM of high-precision determination of 3 coordinates in ELINT stations, based on measuring two distance differences and direction finding (DF) in the elevation plane, can, with a smaller number of side stations (two instead of three), provide accuracy no worse than the known TDOAM. However, this requires that the RMSE value for DF in elevation should be tenths of degrees. The practical application of HM is possible for the issuance of target designations on air defense missile systems radar.

Non-contact measurement method of displacement of spherical joints in long-span space steel structures

For long-span space steel structures after a long period of operation, it is crucial to quickly and accurately measure the deformation for structural safety evaluation. To address the challenges in deformation measurement of space steel structures, this paper presents a non-contact, three-dimensional coordinate measurement method for key ball joints in their spatial positions. A high-precision Laser Total Station is utilized to measure the surface of the ball joints at multiple points. Three-dimensional coordinates of the center of the ball joints are then accurately determined by using three-dimensional analytical method and the least square error method. Subsequently, the deformation of key joints of the long-span space structures is obtained by comparing the determined coordinates with their initial coordinates. An engineering application by adopting the propose method to measure the deformation of a large-span steel structure gymnasium in Guangdong Province is presented. This method not only can be used to evaluate the safety of existing space steel structures, but also can be applied to rapid measurements and positioning of new long-span steel structures to improve the measurement efficiency and personnel safety.

An accurate and robust visual-inertial positioning method

The human–machine integrated coordinate measurement is a promising coordinate measurement method with high flexibility and efficiency for the complex working environments. The cameras installed on the head-mounted measurement device achieves accurate global positioning by observing the uncoded LED landmarks, and then combines with the local measuring to obtain 3D coordinates. However, limited by the frame rate of the camera, the fast movements of the operator’s head may cause landmark misidentification and visual positioning failure. In order to improve the robustness, a visual-inertial positioning method is proposed in this paper. An inertial measurement unit (IMU) is added to compensate for the deficiency of the visual positioning and enhance the dynamic performance. An adaptive extended Kalman filter (EKF), which adjusts the measurement noise covariance matrix based on the visual positioning uncertainty, is established to obtain the optimal state estimation. And an efficient initialization procedure is presented to implement the initial registration of uncoded landmarks based on the normal distribution transform algorithm and to determine the initial state of the IMU. Furthermore, the residual chi-square test is employed to detect false pose estimate in real time and to avoid positioning failure. The experiments demonstrate that the proposed method has high static positioning accuracy (0.681 mm) and high dynamic positioning robustness. The adaptive EKF realizes reliable landmark identification under fast movements and provides a higher accuracy than the common EKF.

Residual stress analysis in AISI 347L steel coating welding on Cr-Mo steel using coordinate measurement method

RESUMO Este estudo avaliou a qualidade do revestimento de aço inoxidável AISI 347L em substrato de aço Cr-Mo produzido pelo processo GMAW, levando em consideração a influência dos parâmetros de soldagem e dos tratamentos térmicos de alívio de tensão. Para a análise de tensão residual, foi utilizado o método de Deslocamento de Pontos Coordenados (DCP). Foram confeccionados três (3) corpos de prova com dimensões de 300 × 150 × 12,7 mm, variando a composição do gás de proteção (100% Ar, 98% Ar + 2%CO2 e 96% Ar + 4% CO2), e realizados tratamentos térmicos pós-soldagem em conformidade com a norma ASME BPVC VIII. Para avaliar a microestrutura do revestimento, foram realizadas análises de microscopia óptica, ensaio macrográfico e ensaio de dureza. Os resultados obtidos indicam que os tratamentos térmicos de alívio de tensão foram eficazes na redução da tensão residual, melhorando a qualidade do revestimento. A análise de microscopia óptica revelou uma microestrutura homogênea e sem trincas ou porosidades, indicando um bom desempenho do processo GMAW. Os resultados desses ensaios são de grande importância para a qualificação do procedimento de soldagem e para garantir a qualidade do revestimento em aplicações práticas.

Analysis of the Teaching Path of Animation Film Majors Integrating Digital Visual Space in the Context of Digital Media Art

Abstract In this study, we first adopt the dynamic stereo vision spatial coordinate measurement method of non-zoom cameras, establish a coordinate measurement model based on differential GPS, and study the application of the spatial coordinates of dynamic stereo digital vision systems in animation design. Secondly, the internal and external parameters of the camera are defined as the static error of the dynamic stereo vision system so as to provide an easy and quick-to-use design tool for the teaching of animation film majors. Finally, a test sequence animation sample set is used to verify the teaching effect of digital visual space based on animation design. The results show that in the multi-comparison test of animation quality against pixel bit rate, the animation design samples were found to have frame rates in the range of 5-30 Fps. And under the condition of having extra bandwidth, the animation feature learning evaluation dimension is 2589, and increasing the animation visual frame rate can improve the output picture quality of animation more effectively. It shows that the integration of digital visual space in the context of digital media art can allow students to have enough project sources for learning and practicing so as to improve their professional ability.

Multi-target automatic positioning based on angle and distance parallel measurement

Precisely and efficiently measuring three-dimensional coordinates of key points on large-scale components in the manufacturing process of aircraft and ships is critically essential. This study presents a multi-target automatic positioning method based on rapid angle and distance measurement in parallel. The measurement processes for angles and distances are decoupled and, when executed simultaneously, aims to enhance the measurement efficiency and automation compared with conventional metrology systems. A cooperative target is devised to realize the rotary-laser scanning angle measurement and absolute distance measurement in parallel. The method of multi-target rough positioning based on rotary-laser scanning and then the precise coordinate measurement method introducing absolute distance constraint are detailed. Especially for the distance measurement, we propose a method to determine the internal zero length and compensate for the distance error caused by mirror offset. A real-site experiment is implemented to verify the method's feasibility and demonstrate that the 3D coordinate measurement accuracy is better than 0.17 mm compared with laser tracker.

Accuracy improvement of a 3D passive laser tracker for the calibration of industrial robots

The laser tracker has been used as the mainstream instrument for the position accuracy calibration of industrial robots for quite a long time. However, due to the complexity of the built-in dual-axis active servo tracking system, its cost is high and the target reflector has to adjust its pose frequently, so it cannot be popularized in the production and application sites of industrial robots. Based on this drawback, a 3D passive laser tracker (3DPLT) with high precision, simple structure, easy operation and low cost is proposed in this paper. Firstly, the overall structure of the system is designed, and its position error model based on the principle of spherical coordinate measurement and vector transfer method is established. Then, the error parameters are identified by experiments to formulate the error compensation model. Finally, the multi-pose and large-range spatial error compensation verification experiments of the system are carried out on a commercial coordinate measuring machine. The results show that the spatial volumetric errors of the 3DPLT can achieve within 40 μm after compensation with a good repeatability of ±4 μm. A comparison contouring test with a commercial ballbar is also carried out to validate its applicability of robot calibration.

Novel laser tracking measurement system based on the position sensitive detector.

The rapid development of modern industrial technology has led to the increase of machinery precision. Laser tracking measurement systems represent a novel type of coordinate measurement method, which was developed on the basis of metrology. In this paper, we aim to define a single-station 3D coordinate rotating laser tracking measurement system based on the principle of the space coordinate method. In view of the current architecture and optical path of the system, we establish the ideal mathematical model of the system and derive the coordinate expression for arbitrary measured points in the measurement space. The output response of the photoelectric position detector to the rotating laser and the linearity of the position signal in the detection circuit have been detected via a concrete experiment. A laser tracking system was used to track the target mirror mounted on the coordinate measuring machine measuring spindle. It is shown that stable tracking is possible during the 3D movement of a cat's eye retroreflector if its velocity is 0.2 m/s and the distance to the moving object is 1-2 m. The corresponding velocity of the object must be 0.4 m/s. Our system provides a feasible implementation method for the tracking of the moving target space position.

A Noncontact Cutterhead Dynamic Coordinate Measurement Method for Double-Shield TBM Guidance Based on Photographic Imaging

This article presents a novel noncontact real-time dynamic coordinate measurement method based on photographic imaging for double-shield tunnel boring machine (TBM) guidance. The method is realized by a photoelectric target, an industrial camera, a laser target, and a total station through a coordinate transformation algorithm. The photoelectric target and the camera are fixed on the rear end-face of the front shield and the front end-face of the support shield, respectively. The camera captures the image of the photoelectric target to calculate the pose of the photoelectric target. Then, the 3-D coordinate of the cutterhead center is measured in real time by the coordinate transformation chain. Subsequently, the guidance of the double-shield TBM is accomplished by comparing the 3-D coordinate with the designed tunnel axis. Under vibration conditions where the frequency is 10 Hz, the standard deviation of horizontal/vertical deviation is better than 4 mm, and the standard deviation of yaw, pitch, and roll angle is better than 0.08°. In a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3\,\,\text {m} \times 2\,\,\text {m} \times 6\,\,\text {m}$ </tex-math></inline-formula> measurement volume, the static position measurement accuracy is better than 5 mm. Experimental results show that the method is feasible and valid for the double-shield TBM guidance system.

Full space coordinate measurement method with a portable light pen by using hybrid light field imaging.

The light pen is one of the most useful spatial coordinate measurement methods. However, due to the principle of vision measurement, the traditional light pen has the disadvantages such as limited measurement range, large structure size and complex calibration process. In order to revolutionize the design of light pen, this paper proposes a full space coordinate measurement method with a portable light pen by using hybrid light field imaging. Firstly, a light field imaging system with depth estimation ability has been introduced to simplify the light pen structure to three target points by using P3P method. In order to improve the accuracy of the depth estimation, a hybrid imaging method and EPI method have been used. Secondly, a full spatial measurement method with a rotation platform has been presented in detail. Finally, the experiments have been designed to verify the effectiveness and accuracy of the proposed method.

Geometric analysis of injection-molded polymer gears (Rapid communication)

Properties of polymer gears were tested using coordinate measurement methods. This study is a follow-up to research on geometric accuracy of gears manufactured by injection molding. Spur gears were measured on a coordinate measuring machine running the GINA software by Klingelnberg. Measurement results were output in the form of measurement sheets which included values required in the DIN 3962 standard. The article also analyses the topography of test gear teeth. The topography was presented for a single tooth of the gear and determined on the basis of the measurements of 9 profiles distributed evenly over a specific profile assessment interval (interval Lα defined in the standard) and 7 tooth traces located within a relevant tooth trace assessment interval (interval Lβ defined in the standard). All gears tested in this study were placed outside accuracy class 12.

Coordinate stitching measurement of highly steep freeform surfaces

A coordinate measuring machine (CMM) is widely used for surface measurement during milling and grinding of workpieces. However, the measurement uncertainty increases with the surface slope for highly steep freeform surfaces. In addition, local features sometimes exist on the surface out of the accessible space of the CMM. This study presents a coordinate measurement method based on stitching multiple subpatches. The complex freeform surface of a large slope is first divided into subpatches which are individually tilted and measured with smaller uncertainty due to reduced slopes. A global stitching algorithm is then proposed to compensate the motion error and stitch all the subpatches together simultaneously, based on configuration optimization to minimize the overlap inconsistency. The coordinate stitching measurement method is first validated through simulation, which shows that the motion error of the order of 0.05°/0.5 mm is tolerable for a highly steep surface. It is then experimentally verified using the stitching measurement of an optical spherical surface and a steep freeform surface. An ordinary multi-axis adjustment stage is suitable for subpatch repositioning because the stitching algorithm compensates the motion error to a level lower than the CMM uncertainty.

Development of tactile sensor using stereo fisheye camera by rotation

In this paper, we propose a 3D coordinate measurement method using a stereo fisheye camera using rotation for tactile sensors.A soft haptic interface by an optical method using a camera has simple wiring and the like, and has a point that it does not impair the mechanical properties of a flexible outer skin and is strong against noise. On the other hand, since many ranges inside the sensor are used for sensing, there is a disadvantage that the usable range inside is narrow. In this paper, we propose a three-dimensional coordinate estimation method using the rotation of a fish-eye camera to expand the usable range inside the tactile sensor. Experimental results show the effectiveness of the proposed method.

Prediction of three-dimensional coordinate measurement of space points based on BP neural network

In order to improve the measurement accuracy of three-dimensional coordinate measurement system based on dual-PSD, this paper proposes a three-dimensional coordinate measurement method based on back propagation (BP) neural network considering the high ability of the neural network to deal with the complex nonlinear mapping problem. This method can describe the mapping relationship between three-dimensional coordinates of space points in the world coordinate system and coordinates of light spots on dual-PSD well. Levenberg-Marquardt learning algorithm is used to train the network, and then trained BP neural network model is used to predict three-dimensional coordinates of space points. Experimental results show that the average measurement error of space points obtained by the method is low. It proves that the built BP neural network model can be used to predict three-dimensional coordinates of space points. [Submitted 9 July 2018; Accepted 30 October 2018]

Measurement of Intra-Orbital Structures in Normal Chinese Adults Based on a Three-Dimensional Coordinate System

ABSTRACT Purpose of the study This study was to establish a three-dimensional (3D) coordinate system and to study the normal dimensions of intra-orbital structures in Chinese adults. Materials and methods One hundred and forty-five adult Chinese were selected from patients who had undergone cranio-facial computed tomography scans with diagnosis other than orbital or ocular abnormality. An orbital 3D coordinate system was built on the basis of the scans. Morphological variables of intra-orbital structures were measured in this coordinate system. Bilateral symmetry, sexual dimorphism, and correlations between variables were investigated. Results No evident laterality was found in bilateral intra-orbital structures. The distance from the center of the eyeball to the prechiasmatic groove, the length of the optic nerve, and the thickness of rectus extraocular muscles were larger in males than in females. No sex-related difference was observed in the anteroposterior diameter of the eyeball or the exophthalmometric value. The exophthalmometric value was found to be related to the anteroposterior diameter of the eyeball, whereas the y-coordinate of the center of the eyeball had no correlation with the anteroposterior diameter of the eyeball. The optic nerve length was closely correlated to the distance from the center of the eyeball to the prechiasmatic groove. Conclusions The 3D coordinate system and measurement method established in this study can be applied to the standardization of orbital morphometry. The measurements obtained from normal Chinese adults may provide reference values for the morphology of intra-orbital structures.

DEM和单相机的弹落点坐标测量方法

DEM和单相机的弹落点坐标测量方法

Wide Range Coordinate Measurement Method under Small Field of View

Wide Range Coordinate Measurement Method under Small Field of View

基于正交柱面成像相机空间后方交会的三维坐标测量方法

基于正交柱面成像相机空间后方交会的三维坐标测量方法

The use of the photogrammetric method for measurement of the repose angle of granular materials

The paper addresses a vitally important issue of precise determination of the angle of repose of granular materials. For calculation of the said angle, a photogrammetric 3D coordinate measurement method has been proposed. With the view of method verification, 600 independent measurement results were obtained, based on which the angle of repose of examined plant granular materials (triticale) was determined with a statement of the associated measurement uncertainty. The conducted analysis has shown that the proposed method is useful and capable of low (as for biological materials) measurement uncertainty congruent with the requirements of automated systems, and as such may be helpful in laying down the standard specification for measuring of the angle of repose, using coordinate metrology.