Reference Coordinate System Research Articles

PAM: Research on posture alignment method for camera robot system

By acquiring the posture information of the rigid body with markers, the camera motion on the robot end-effector can be controlled remotely. The essential step of posture alignment in teleoperation is to calibrate the transformation matrix of the world coordinate system of the optical motion capture system and the robot base coordinate system. It was necessary to change the position and attitude of the camera robot in the studio frequently. At the same time, the studio was complex with strong personnel mobility, thus the world coordinate system of the optical tracking system in the studio was needed to be re-established frequently. These two points asked the pose calibration scheme of the camera robot in the optical tracking system to be convenient and universal. In this paper, a novel posture alignment method (PAM) was proposed, which was an automatic, accurate and quick method to complete the posture alignment for related coordinate systems without non-systematic errors. PAM was applied to teleoperation for camera robot by inverse movement matrix. The comparative experiments prove that the proposed method is better than manual method, with higher precision and stability, more flexible physical setting for reference coordinate system, and shorter operation time consuming. Meanwhile, PAM is more suitable for camera robot teleoperation than existed automatic method, because it does not require paying attention to the calibration postures.

Evaluation of Anatomical Landmark Consistency in the Auditory Meatus Using Cone-Beam Computed Tomography (CBCT) Imaging

IntroductionThe present study evaluated the consistency and reliability of five anatomical landmarks in the external auditory meatus using CBCT (cone beam computed tomography) scans. The goal was to determine if these landmarks could reliably replace the commonly used point Porion for superimposing CBCT scans in clinical practice. Consistent anatomical features in the external auditory meatus are essential for accurate cranial assessments in dentistry and medicine. Despite their importance, these features have been underexplored, making this study a valuable contribution to improving clinical evaluation accuracy. Materials and methods22 CBCT scans were analyzed using ITK-Snap software. The shape of the External Auditory Meatus had been rendered by segmentation. These segmentations were used as a basis to locate the landmarks. The spread in location of the suggested landmarks concerning a reference coordinate system was treated as a measure for consistency. For that purpose, the absolute mean distance from all registered landmarks to the center of the location cloud was calculated for each dataset. ResultsThe smallest spread in locations was measured for the so-called Epitympanic Notch, with 4.3 mm on average (SD 1.7). However, recognizing this landmark in the segmented images appeared to be relatively difficult. The landmark with the second smallest spread in locations (4.4 mm (SD 2.2)) and an easier recognition in the segmented image was the most superior point of the external auditory meatus. The most inferior point appeared to be the least reliable of all five landmarks. ConclusionBased on the present study, a consistently reliable landmark in the External Auditory Meatus to replace point Porion could not be identified. The hypothesis that any landmark could suffice for superimposing CBCT scans was not confirmed.

Comparative Analysis of GDM2000, WGS84, and MRT68 Coordinate Reference Systems based on Different Converter Modules

Comparative Analysis of GDM2000, WGS84, and MRT68 Coordinate Reference Systems based on Different Converter Modules

Influence of tunnel cone angle and lip deflection on the performance of coaxial twin propeller

Abstract To investigate the influence of the culvert cone angle and the angle of the mouth on the aerodynamic performance of the culvert coaxial twin rotor and its mechanism, the quasi-steady numerical simulation of the flow field of the culvert coaxial twin rotor under a hovering state was carried out based on the Reynolds mean Navier-Stokes (RANS) equation and the multiple reference coordinate system method (MRF). The influence of cone angle from -6° to 9° and lip deflection angle from -20° to 30° on the aerodynamic performance of coaxial double-rotors with ducted passages is analyzed. The results show that the contractile culvert can generate a large gain lift force, which is conducive to improving the aerodynamic efficiency of the system. The inward deflection of the lip obstructs the flow of air into the culvert, which will worsen the local aerodynamic environment and lead to serious air separation, increasing the power consumption of the system. However, the structure of the outward deflection of the lip (open culvert) better complies with the flow trend of air, helps to reduce aerodynamic interference, and improves the additional lift of the culvert, which is beneficial to improving the aerodynamic performance of the system.

The Kinematic Models of the SINS and Its Errors on the SE(3) Group in the Earth-Centered Inertial Coordinate System.

In this paper, the kinematic models of the Strapdown Inertial Navigation System (SINS) and its errors on the SE(3) group in the Earth-Centered Inertial frame (ECI) are established. On the one hand, with the ECI frame being regarded as the reference, based on the joint representation of attitude and velocity on the SE(3) group, the dynamic of the local geographic coordinate system (n-frame) and the body coordinate system (b-frame) evolve on the differentiable manifold, respectively, and the high-order expansion of the Baker-Campbell-Haussdorff equation compensates for the non-commutative motion errors stimulated by strong maneuverability. On the other hand, the kinematics of the left- and right-invariant errors of the n-frame and the b-frame on the SE(3) group are separately derived, where the errors of the b-frame completely depend on inertial sensor errors, while the errors of the n-frame rely on position errors and velocity errors. In this way, the errors brought by the inconsistency of the reference coordinate system are tackled, and a novel attitude error definition is introduced to separate and decouple the factors affecting the dynamic of the n-frame errors and the b-frame errors for better attitude estimation. Through a turntable experiment and a car-mounted field experiment, the effectiveness of the proposed kinematic models in estimating attitude has been verified, with a remarkable improvement in yaw angle accuracy in the case of large initial misalignment angles, and the models developed have better robustness compared to the traditional SE(3) group-based model.

CRUSTAL DEFORMATIONS AND THEIR IMPACT ON THE REALIZATION OF A NATIONAL COORDINATE REFERENCE SYSTEM: CASE STUDY AETOLIA-ACARNANIA, WESTERN GREECE

<p>Geodesy and crustal deformations are closely related. On the one hand, geodetic techniques are used to estimate deformations contributing in this way to geology, seismology and geodynamics. On the other hand, deformations consist a major challenge in the maintenance of geodetic reference frames. In this work we use GNSS (Global Navigation Satellite System) data and geodetic methods to estimated crustal deformations in the area of Aetolia-Acarnania, western Greece. The analysis of measurements that have been conducted in 2007 and 2023 on trigonometric points showed significant horizontal deformations up to 16.8 cm. The revealed deformations are presented and discussed in terms of their impact on the realization of the national coordinate reference system.</p>

DNA-m6A calling and integrated long-read epigenetic and genetic analysis with fibertools.

Long-read DNA sequencing has recently emerged as a powerful tool for studying both genetic and epigenetic architectures at single-molecule and single-nucleotide resolution. Long-read epigenetic studies encompass both the direct identification of native cytosine methylation and the identification of exogenously placed DNA N 6 -methyladenine (DNA-m6A). However, detecting DNA-m6A modifications using single-molecule sequencing, as well as coprocessing single-molecule genetic and epigenetic architectures, is limited by computational demands and a lack of supporting tools. Here, we introduce fibertools, a state-of-the-art toolkit that features a semisupervised convolutional neural network for fast and accurate identification of m6A-marked bases using Pacific Biosciences (PacBio) single-molecule long-read sequencing, as well as the coprocessing of long-read genetic and epigenetic data produced using either the PacBio or Oxford Nanopore Technologies (ONT) sequencing platforms. We demonstrate accurate DNA-m6A identification (>90% precision and recall) along >20 kb long DNA molecules with an ∼1000-fold improvement in speed. In addition, we demonstrate that fibertools can readily integrate genetic and epigenetic data at single-molecule resolution, including the seamless conversion between molecular and reference coordinate systems, allowing for accurate genetic and epigenetic analyses of long-read data within structurally and somatically variable genomic regions.

GEOGRAPHIC INFORMATION MODEL OF PRECIPITATION INTENSITY

The paper analyses the technological features of building a geoinformation model to study the precipitation intensity in Ukraine. Analysis of natural phenomena requires promptness in obtaining and updating initial data. For this reason, today, geoinformation technologies most often use remote sensing data, mainly in raster format. We collected the raw data on precipitation intensity from the Global Precipitation Climatology Centre website of the German Meteorological Service (DWD). It is monthly data for 2022 in raster format with a raster size of 1 degree. For the organisation and analysis of geographical information, we chose the most suitable new software product, SAGA GIS, designed for geoscientific analysis automation. The advantages of this system are the availability of a complete set of geophysical analysis methods, the spatial algorithms implementation, and open-source code. After data loading, we geoprocessed the data, in particular, using the SAGA software module ‘Set Coordinate Reference System’ and selected the WGS84 coordinate system for the required layers. To prepare the data for analytical studies, we limited them to the administrative boundaries of Ukraine and transformed the WGS84 coordinate system into a UTM 36N projection. Using SAGA analytical tools, we grouped the data by season. Then, we determined the distribution of precipitation intensity over the territory for each season, identifying areas with the highest and lowest precipitation intensity and a part of the territory with the highest annual precipitation. The results of this work may have practical significance for various sectors of the economy and decision-making on adaptation to climate change. They can be relevant both for scientific research and practical application in fields related to environmental assessment. By supplementing the model with data for other subsequent or previous periods, it will be possible to determine trends in precipitation intensity by regions of Ukraine or physiographic zones of its territory. Keywords: modelling, precipitation intensity, geodatabase, geoprocessing, seasonality, software modules, SAGA GIS.

Free vibration analysis of laminated anisotropic doubly-curved shell structures reinforced with three-phase polymer/CNT/fiber material

The present work investigates the vibrational response of laminated anisotropic doubly-curved shell structures reinforced with Carbon Nanotubes (CNTs) short fibers. The fundamental equations are derived from a curvilinear reference system of principal coordinates, employing the Equivalent Single Layer (ESL) methodology. Furthermore, a general variation in laminate thickness is considered. The unknown field variable is described using higher order theories through the unified formulation, taking into account a general interpolation of the unknown variables with Lagrange polynomials across the physical domain. The Hamiltonian Principle is adopted for the derivation of the dynamic equilibrium equations, which arediscretized numerically by using the Generalized Differential Quadrature (GDQ) method. In addition, an efficient isogeometric NURBS-based mapping is adopted for the distortion of the physical domain. The boundary conditions of the differential problem are modelled through a general distribution of linear elastic springs along the lateral surfaces of the three-dimensional doubly-curved solid. The theory is then applied to study the vibrational modes of structures with different curvatures and lamination schemes, taking into account a general distribution of CNTs along the thickness direction. The homogenized properties of CNTs layers are obtained from the Mori-Tanaka procedure, which accounts for the agglomeration effects of the dispersed nanofibers within the matrix. Unlike previous studies focusing on doubly-curved shells reinforced with composite materials and CNTs, the present formulation enables to derive the vibration characteristics of structures made of generally anisotropic materials with general orientations. Furthermore, the calibration of the parameters for the linear elastic springs’ distribution leads to general external constraints within a single element, thus reducing the computational cost of the problem.

Talus-derived reference coordinate system for 3D calcaneal assessment: A novel approach to improve morphological measurements.

In 3D-analysis of the calcaneus, a consistent coordinate system aligned with the original anatomical directions is crucial for pre- and postoperativeanalysis. This importance stems from the calcaneus's key role in weight-bearing and biomechanical alignment. However, defining a reliable coordinate system based solely on fractured or surgically reconstructed calcanei presents significant challenges. Given its anatomical prominence and consistent orientation, the talus offers a potential solution to this challenge. Our work explores the feasibility of talus-derived coordinate systems for 3D-modeling of the calcaneus across its various conditions. Four methods were tested on nonfractured, fractured and surgically reconstructed calcanei, utilizing Principal Component Analysis, anatomical landmarks, bounding box, and an atlas-based approach. The methods were compared with a self-defined calcaneus reference coordinate system. Additionally, the impact of deviation of the coordinate system on morphological measurements was investigated. Among methods for constructing nonfractured calcanei coordinate systems, the atlas-based method displayed the lowest Root Mean Square value in comparison with the reference coordinate system. For morphological measures like Böhler's Angle and the Critical angle of Gissane, the atlas talus-based system closely aligned with ground truth, yielding differences of 0.6° and 1.2°, respectively, compared to larger deviations seen in other talus-based coordinate systems. In conclusion, all tested methods were feasible for creating a talus derived coordinate system. A talus derived coordinate system showed potential, offering benefits for morphological measurements and clinical scenarios involving fractured and surgically reconstructed calcanei. Further research is recommended to assess the impact of these coordinate systems on surgical planning and outcomes.

Reconstruction of occluded pelvis markers during marker-based motion capture with industrial exoskeletons

Industrial back support exoskeletons are a promising solution to alleviate lumbar musculoskeletal strain. Due to the complexity of spinal loading, evaluation of EMG data alone has been considered insufficient to assess their support effects, and complementary kinematic and dynamic data are required. However, the acquisition of marker-based kinematics is challenging with exoskeletons, as anatomical reference points, particularly on the pelvis, are occluded by exoskeleton structures. The aim of this study was therefore to develop and validate a method to reliably reconstruct the occluded pelvic markers. The movement data of six subjects, for whom pelvic markers could be placed while wearing an exoskeleton, were used to test the reconstructions and compare them to anatomical landmarks during lifting, holding and walking. Two separate approaches were used for the reconstruction. One used a reference coordinate system based on only exoskeleton markers (EXO), as has been suggested in the literature, while our proposed method adds a technical marker in the lumbar region (LUMB) to compensate for any shifting between exoskeleton and pelvis. Reconstruction with EXO yielded on average an absolute linear deviation of 54 mm ± 16 mm (mean ± 1SD) compared to anatomical markers. The additional marker in LUMB reduced mean deviations to 14 mm ± 7 mm (mean ± 1SD). Both methods were compared to reference values from the literature for expected variances due to marker placement and soft tissue artifacts. For LUMB 99% of reconstructions were within the defined threshold of 24 mm ±9 mm while for EXO 91% were outside.

Examining honey production with Geographic Information Systems (GIS): The example of Ordu province

Beekeeping is an example of economic farming with its products that can be done without being dependent on plant and ecological production because of its contribution to pollination. This study aims to examine Ordu province, which has been at the top of Turkey's beekeeping activities and honey production for years, with Geographic Information Systems (GIS) based on honey production data between 2013 and 2022. By evaluating the honey production data of registered breeders in Ordu province, cartographic maps were produced to evaluate the spatial projection of honey production for the last ten years. After creating a GIS-based database, district-based shape file (.shp extension) data was used for spatial analysis and mapping of the obtained outputs. After these data were defined in the WGS 84 EPSG:4326 coordinate reference system, the spatial distribution of honey production and yield throughout the study period was analyzed using the open-source QGIS version 3.18.3 software. It was determined that the highest honey production belonged to registered beekeepers in Altınordu district during the relevant time period. Altınordu is also the district with the highest number of registered enterprises. It was determined that the honey production data and the number of enterprises of the beekeepers in Gülyalı district, which is one of the neighbouring districts of this district, are lower than Altınordu district. After Altınordu district, Perşembe, Ulubey, Gürgentepe and Gölköy districts have an important place in honey production. Although these districts are neighbours like Gülyalı district, their high production may have resulted from the difference in cooperation between the districts. As a result, it was determined that honey production activities in Ordu province and districts, which is an important city in terms of honey production, vary depending on the districts. The problem of climate change, which is predicted that the world will be exposed to more in the near future, also directs beekeeping activities towards nomadic beekeeping. It can be said that like most of the breeders in Ordu province, registered beekeepers in other cities will be more orientated towards nomadic beekeeping against the threat of global warming.

Object-based terminal positioning solution within task-boosted global constraint for improving mobile robotic stacking accuracy

Wall building is labor-intensive and time-consuming as a typical construction task. It is expected to perform this heavy task using robots. However, laborers are still largely employed, mainly because high continuous stacking precision for mobile robots has always been a bottleneck problem. This paper examines the characteristics of continuous robotic stacking in wall-building tasks and finds the key challenge lies in precisely manipulating the robot arm terminal to the target pose and guaranteeing the wall’s verticality. We propose an object-based terminal positioning solution for this issue. The core of this solution is establishing a reference coordinate system as a measurement reference and designing a multi-sensor measurement system to measure the relative pose between the robot and the object. The solution allows the robot to reposition multiple times and iteratively correct the terminal’s pose, which greatly reduces the impact of positioning errors and loaded deflections of mobile systems on terminal positioning accuracy. Furthermore, we propose for the first time the construction of an active reference feature using a planar laser as a global constraint to provide a consistent reference for establishing reference coordinate systems. Global constraint eliminates the cumulative stacking errors due to relying only on the previously stacked object’s reference features for terminal positioning in continuous stacking tasks and guarantees the wall’s verticality. Finally, an autonomous mobile stacking robot is developed, and continuous block stacking experiments are conducted with this robot in a laboratory environment simulating real application sites. Experimental results demonstrate that the developed robotic system can achieve millimeter-level stacking accuracy, where a single vertical stack error of 3 mm meets the high requirements of the construction industry. Thus, it is reasonable to believe the proposed solution is extremely competitive compared to existing studies and provides valuable insights for improving the continuous stacking accuracy of mobile robots in large-scale unstructured environments.

Best BiCubic Method to Compute the Planimetric Misregistration between Images with Sub-Pixel Accuracy: Application to Digital Elevation Models

In recent decades, an important number of regional and global digital elevation models (DEMs) have been released publicly. As a consequence, researchers need to choose between several of these models to perform their studies and to use these DEMs as third-party data to compute derived products (e.g., for orthorectification). However, the comparison of DEMs is not trivial. For most quantitative comparisons, DEMs need to be expressed in the same coordinate reference system (CRS) and sampled over the same grid (i.e., be at the same ground sampling distance with the same pixel-is-area or pixel-is-point convention) with heights relative to the same vertical reference system (VRS). Thankfully, many open tools allow us to perform these transformations precisely and easily. Despite these rigorous transformations, local or global planimetric displacements may still be observed from one DEM to another. These displacements or disparities may lead to significant biases in comparisons of DEM elevations or derived products such as slope, aspect, or curvature. Therefore, before any comparison, the control of DEM planimetric accuracy is certainly a very important task to perform. This paper presents the disparity analysis method enhanced to achieve a sub-pixel accuracy by interpolating the linear regression coefficients computed within an exploration window. This new method is significantly faster than oversampling the input data because it uses the correlation coefficients that have already been computed in the disparity analysis. To demonstrate the robustness of this algorithm, artificial displacements have been introduced through bicubic interpolation in an 11 × 11 grid with a 0.1-pixel step in both directionsThis validation method has been applied in four approximately 10 km × 10 km DEMIX tiles showing different roughness (height distribution). Globally, this new sub-pixel accuracy method is robust. Artificial displacements have been retrieved with typical errors (eb) ranging from 12 to 20% of the pixel size (with the worst case in Croatia). These errors in displacement retrievals are not equally distributed in the 11 × 11 grid, and the overall error Eb depends on the roughness encountered in the different tiles. The second aim of this paper is to assess the impact of the bicubic parameter (slope of the weight function at a distance d = 1 of the interpolated point) on the accuracy of the displacement retrieval. By considering Eb as a quality indicator, tests have been performed in the four DEMIX tiles, making the bicubic parameter vary between −1.5 and 0.0 by a step of 0.1. For each DEMIX tile, the best bicubic (BBC) parameter b* is interpolated from the four Eb minimal values. This BBC parameter b* is low for flat areas (around −0.95) and higher in mountainous areas (around −0.75). The roughness indicator is the standard deviation of the slope norms computed from all the pixels of a tile. A logarithmic regression analysis performed between the roughness indicator and the BBC parameter b* computed in 67 DEMIX tiles shows a high correlation (r = 0.717). The logarithmic regression formula b~σslope estimating the BBC parameter from the roughness indicator is generic and may be applied to estimate the displacements between two different DEMs. This formula may also be used to set up a future Adaptative Best BiCubic (ABBC) that will estimate the local roughness in a sliding window to compute a local BBC b~.

An exact system of generation for face-milled hypoid gears with uniform depth taper: Application to hypoid gear drives with high gear ratio

An exact system of generation for face-milled hypoid gears with uniform depth taper is proposed. This system defines the location of pinion and wheel, their respective cutting (or grinding) cutters, and the relations of motion in their respective reference coordinate systems attached to the cutting machine. As a result, the grinding cutter geometric parameters and basic machine-tool settings are analytically determined without the need of any further optimization process. The appropriate selection of the mean cutter radius is addressed following the recommendations of the Information Sheet AGMA ISO 22849-A12. The tooth contact analysis of the gear drive shows a localized bearing contact with no unloaded transmission errors in the absence of misalignments. A lower sensitivity of the contact pattern to errors of alignment is observed as the mean cutter radius is decreased. Stress analysis shows that only the application of a tip relief is needed to avoid edge contacts at the tip of the gear tooth surfaces, being the point width of the cutting blades a key parameter to balance bending stresses in the pinion and the wheel.

Phybers: a package for brain tractography analysis.

We present a Python library (Phybers) for analyzing brain tractography data. Tractography datasets contain streamlines (also called fibers) composed of 3D points representing the main white matter pathways. Several algorithms have been proposed to analyze this data, including clustering, segmentation, and visualization methods. The manipulation of tractography data is not straightforward due to the geometrical complexity of the streamlines, the file format, and the size of the datasets, which may contain millions of fibers. Hence, we collected and structured state-of-the-art methods for the analysis of tractography and packed them into a Python library, to integrate and share tools for tractography analysis. Due to the high computational requirements, the most demanding modules were implemented in C/C++. Available functions include brain Bundle Segmentation (FiberSeg), Hierarchical Fiber Clustering (HClust), Fast Fiber Clustering (FFClust), normalization to a reference coordinate system, fiber sampling, calculation of intersection between sets of brain fibers, tools for cluster filtering, calculation of measures from clusters, and fiber visualization. The library tools were structured into four principal modules: Segmentation, Clustering, Utils, and Visualization (Fibervis). Phybers is freely available on a GitHub repository under the GNU public license for non-commercial use and open-source development, which provides sample data and extensive documentation. In addition, the library can be easily installed on both Windows and Ubuntu operating systems through the pip library.

Impact of radiation dose distribution on nutritional supplementation needs in head and neck cancer radiotherapy: a voxel-based machine learning approach.

To investigate the relationship between nutritional supplementation and radiation dose to the pharyngeal constrictor muscles and larynx for head and neck (HN) cancer patients undergoing radiotherapy. We retrospectively analyzed radiotherapy (RT) dose for 231 HN cancer patients, focusing on the pharyngeal constrictors and larynx. We defined nutritional supplementation as feeding tube utilization or >10% weight loss from baseline within 90 days after radiotherapy completion. Using deformable image registration (DIR), we mapped each patient's anatomical structures to a reference coordinate system, and corresponding deformations were applied to dose matrices. Voxel doses were utilized as features for ridge logistic regression models, optimized through 5-fold cross-validation. Model performance was assessed with area under the curve of a receiver operating curve (AUC) and F1 score. We built and compared models using 1) pharyngeal constrictor voxels, 2) larynx voxels, 3) clinical factors and mean regional dose metrics, and 4) clinical factors and dose-volume histogram metrics. Test set AUCs were compared among the models, and feature importance was evaluated. DIR of the pharyngeal constrictors and larynx yielded mean Dice coefficients of 0.80 and 0.84, respectively. Pharyngeal constrictors voxels and larynx voxel models had AUC of 0.88 and 0.82, respectively. Voxel-based dose modeling identified the superior to middle regions of the pharyngeal constrictors and the superior region of larynx as most predictive of feeding tube use/weight loss. Univariate analysis found treatment setting, treatment laterality, chemotherapy, baseline dysphagia, weight, and socioeconomic status predictive of outcome. An aggregated model using mean doses of pharyngeal constrictors and larynx subregions had an AUC of 0.87 and the model using conventional DVH metrics had an AUC of 0.85 with p-value of 0.04. Feature importance calculations from the regional dose model indicated that mean doses to the superior-middle pharyngeal constrictor muscles followed by mean dose to the superior larynx were most predictive of nutritional supplementation. Machine learning modeling of voxel-level doses enables identification of subregions within organs that correlate with toxicity. For HN radiotherapy, doses to the superior-middle pharyngeal constrictors are most predictive of feeding tube use/weight loss followed by the doses to superior portion of the larynx.

Template-Guided Hierarchical Multi-View Registration Framework of Unordered Bridge Terrestrial Laser Scanning Data.

The registration of bridge point cloud data (PCD) is an important preprocessing step for tasks such as bridge modeling, deformation detection, and bridge health monitoring. However, most existing research on bridge PCD registration only focused on pairwise registration, and payed insufficient attention to multi-view registration. In addition, to recover the overlaps of unordered multiple scans and obtain the merging order, extensive pairwise matching and the creation of a fully connected graph of all scans are often required, resulting in low efficiency. To address these issues, this paper proposes a marker-free template-guided method to align multiple unordered bridge PCD to a global coordinate system. Firstly, by aligning each scan to a given registration template, the overlaps between all the scans are recovered. Secondly, a fully connected graph is created based on the overlaps and scanning locations, and then a graph-partition algorithm is utilized to construct the scan-blocks. Then, the coarse-to-fine registration is performed within each scan-block, and the transformation matrix of coarse registration is obtained using an intelligent optimization algorithm. Finally, global block-to-block registration is performed to align all scans to a unified coordinate reference system. We tested our framework on different bridge point cloud datasets, including a suspension bridge and a continuous rigid frame bridge, to evaluate its accuracy. Experimental results demonstrate that our method has high accuracy.

An efficient method for measuring and identifying geometric and dynamic errors in dual five-axis machine tools

The dual five-axis machining machine is state-of-the-art equipment designed for producing thin-walled aerospace parts like skins and panels. It comprises two five-axis machine tools with mirrored synchronous motions: one bi-rotary machine for milling and the other machine for follow-up support. The high absolute accuracy of the five-axis machine tools themselves and the high synchronous motion accuracy between the two machines are both crucial to ensure machining accuracy. This paper proposes an efficient method to measure and identify geometric and dynamic errors of dual five-axis machine tools. Using the R-test combined with three measurement trajectories to measure the absolute motion error of two five-axis machine tools and the synchronous motion error between the two machines. The designed trajectories include the main rotary axis linkage conditions and can fully reflect the primary motion forms of the dual five-axis machine tool. The main position-independent geometric errors and rotational axis linkage dynamic errors are identified by converting quasi-static and dynamic measurement data from three different trajectories into a unified reference coordinate system. The entire process requires only one instrument installation, effectively avoiding time-consuming repetitive installations and calibration processes while reducing the impact of installation errors on results. The effectiveness of the proposed method for measuring and identifying the geometric and dynamic errors is analyzed combined with Monte Carlo simulation. Experiments were carried out on a dual five-axis mirror milling system (MMS) with a 5000 mm X-stroke. Both simulations and experiments confirmed that the proposed method is efficient in quickly identifying key error sources of the MMS.

3D SPACE KINEMATICS OF A ROBOT FOR PROCESS AUTOMATION IN METALLURGY

3D SPACE KINEMATICS OF A ROBOT FOR PROCESS AUTOMATION IN METALLURGY