Reference Coordinate System Research Articles

Model Predictive Current Control of Traction Permanent Magnet Synchronous Motors in Six-Step Operation for Railway Application

This paper proposes a finite set model predictive current control scheme for traction permanent magnet synchronous motors for railway application. For the rail transit drive system, it is necessary to realize the six-step operation. A method based on voltage vector clamping is presented to realize overmodulation including six-step operation and maximize the utilization ratio of dc voltage. The essence of voltage vector clamping is to gradually reduce the space of action of the closed-loop regulation mechanism until it enters six-step operation. This method is simple and feasible, which does not need to add controllers or switch the control framework. An ideal voltage vector reference coordinate system is established to analyze the current trajectory under different modulation ratios. Thus, an optimal control strategy in the ideal voltage reference coordinate system is proposed. Experiments are conducted to prove that six-step operation can be achieved and this strategy has an obvious effect on switching frequency index in the overmodulation area.

Numerical approach for predicting the slamming loads in oblique long waves considering the wave-body interface

Ship slamming is quite common for ongoing ships, which involves complex wave-body interaction. However, our understanding on the ship slamming is limited to symmetrical cases. In this paper, a numerical approach was established to predict the asymmetric slamming loads in oblique long waves through combining the seakeeping theory and CFD technology. A reference coordinate system located on the wave surface was applied to transfer the ship slamming problems into asymmetrical water entry cases, where the inclination wave-body interface and asymmetrical ship motions were included. Numerical verifications including the CFD method, different water entry models, 3D effects and wave effects were carried out to discuss the applicability. Taking a 21K TEU container ship as an example, the characteristics of slamming loads under oblique long waves were further discussed through combining the free surface evolution and pressure distribution. The results demonstrate that the wave direction has significant influence on the slamming loads. This method can provide a high-efficiency prediction for slamming loads in oblique long waves with reasonable accuracy, which is quite useful at present to serve the impact strength design.

GSPy: A new toolbox and data standard for Geophysical Datasets

The diversity of geophysical methods and datatypes, as well as the isolated nature of various specialties (e.g., electromagnetic, seismic, potential fields) leads to a profusion of separate data file formats and documentation conventions. This can hinder cooperation and reduce the impact of datasets researchers have invested in heavily to collect and prepare. An open, portable, and well-supported community data standard could greatly improve the interoperability, transferability, and long-term archival of geophysical data. Airborne geophysical methods particularly need an open and accessible data standard, and they exemplify the complexity that is common in geophysical datasets where critical auxiliary information on the survey and system parameters are required to fully utilize and understand the data. Here, we propose a new Geophysical Standard, termed the GS convention, that leverages the well-established and widely used NetCDF file format and builds on the Climate and Forecasts (CF) metadata convention. We also present an accompanying open-source Python package, GSPy, to provide methods and workflows for building the GS-standardized NetCDF files, importing and exporting between common data formats, preparing input files for geophysical inversion software, and visualizing data and inverted models. By using the NetCDF format, handled through the Xarray Python package, and following the CF conventions, we standardize how metadata is recorded and directly stored with the data, from general survey and system information down to specific variable attributes. Utilizing the hierarchical nature of NetCDF, GS-formatted files are organized with a root Survey group that contains global metadata about the geophysical survey. Data are then organized into subgroups beneath Survey and are categorized as Tabular or Raster depending on the geometry and point of origin for the data. Lastly, the standard ensures consistency in constructing and tracking coordinate reference systems, which is vital for accurate portability and analysis. Development and adoption of a NetCDF-based data standard for geophysical surveys can greatly improve how these complex datasets are shared and utilized, making the data more accessible to a broader science community. The architecture of GSPy can be easily transferred to additional geophysical datatypes and methods in future releases.

Improved RANSAC Point Cloud Spherical Target Detection and Parameter Estimation Method Based on Principal Curvature Constraint.

Spherical targets are widely used in coordinate unification of large-scale combined measurements. Through its central coordinates, scanned point cloud data from different locations can be converted into a unified coordinate reference system. However, point cloud sphere detection has the disadvantages of errors and slow detection time. For this reason, a novel method of spherical object detection and parameter estimation based on an improved random sample consensus (RANSAC) algorithm is proposed. The method is based on the RANSAC algorithm. Firstly, the principal curvature of point cloud data is calculated. Combined with the k-d nearest neighbor search algorithm, the principal curvature constraint of random sampling points is implemented to improve the quality of sample points selected by RANSAC and increase the detection speed. Secondly, the RANSAC method is combined with the total least squares method. The total least squares method is used to estimate the inner point set of spherical objects obtained by the RANSAC algorithm. The experimental results demonstrate that the method outperforms the conventional RANSAC algorithm in terms of accuracy and detection speed in estimating sphere parameters.

Firepower distribution method of anti-ship missile based on coupled path planning

Anti-ship missile coordinated attack mission planning is a complex multi-objective optimization problem with multiple combinations of platforms, strong decision-making constraints, and tightly coupled links. To avoid the coupling disorder between path planning and firepower distribution and improve the efficiency of coordinated attack mission planning, a firepower distribution model under the conditions of path planning is established from the perspective of decoupling optimization and the algorithm is implemented. First, we establish reference coordinate system of firepower distribution to clarify the reference direction of firepower distribution and divide the area of firepower distribution; then, we construct an index table of membership of firepower distribution to obtain alternative firepower distribution plans; finally, the fitness function of firepower distribution is established based on damage income, missile loss, ratio of efficiency and cost of firepower distribution, and the mean square deviation of the number of missiles used, and the alternatives are sorted to obtain the optimal firepower distribution plan. According to two simulation experiments, the method in this paper can effectively solve the many-to-many firepower distribution problem of coupled path planning. Under the premise of ensuring that no path crossing occurs, the optimal global solution can be obtained, and the operability and timeliness are good.

Evaluation of the Foot Center of Pressure Estimation from Pressure Insoles during Sidestep Cuts, Runs and Walks.

Estimating the foot center of pressure (CoP) position by pressure insoles appears to be an interesting technical solution to perform motion analysis beyond the force platforms surface area. The aim of this study was to estimate the CoP position from Moticon pressure insoles during sidestep cuts, runs and walks. The CoP positions assessed from force platform data and from pressure insole data were compared. One calibration trial performed on the force platforms was used to localize the insoles in the reference coordinate system. The most accurate results were obtained when the motion performed during the calibration trial was similar to the motion under study. In such a case, mean accuracy of CoP position have been evaluated to mm along anteroposterior (AP) axis and mm along mediolateral (ML) axis for sidestep cuts, mm along AP axis and mm along ML axis for runs, mm along AP axis and mm along ML axis for walks. The accuracy of the CoP position assesment from pressure insole data increased with the vertical force applied to the pressure insole and with the number of pressure cells involved.

Monitoring water level and volume changes of lakes and reservoirs in the Yellow River Basin using ICESat-2 laser altimetry and Google Earth Engine

Monitoring the water level and volume changes of lakes and reservoirs is essential for deepening our understanding of the temporal and spatial dynamics of water resources in the Yellow River Basin, with a view to better utilizing and managing water resources. In recent years, there have been many studies on monitoring water level and volume changes in inland waters, but they were mainly focused on radar altimetry and the full waveform LiDAR ICESat, which was retired in 2010. Few studies based on the latest photon-counting LiDAR ICESat-2 have been reported. Compared with previous sensors, ICESat-2 has great advantages in footprint size, transmitting frequency, pulse number, etc, but its performance in monitoring water level and volume changes in inland waters has not been fully explored. Here we investigated the spatial distribution of water level and volume changes of 11 lakes and 8 reservoirs in the Yellow River Basin based on ICESat-2 and Google Earth Engine, and analyzed the factors affecting the measurement uncertainties. In-situ validation of lake level in Lake Qinghai indicates that the Root Mean Square Error (RMSE) of our result is only 7 cm after the reference coordinate system conversion. We found that the water level trend of the natural lake shows significant seasonal variations, while the water level trend of the reservoir shows a sharp rise and fall. In addition, precipitation plays a decisive role in the changes in natural lake levels and indirectly affects the artificial control of reservoirs’ water discharges. The uncertainty of water volume change monitoring is mainly affected by water level measurement uncertainty for lakes, while for reservoirs, that is affected by the combination of water level and area measurement uncertainties. The stability of lake level measurement increases with the increase in photon counts. The introduction of ICESat-2 ATL13 Significant Wave Height might lead larger standard deviation in water level measurement. According to the law of propagation of uncertainty, the uncertainty of the water volume change estimation by the combination of ICESat-2 and GEE is less than 9 %.

Application of nonlinear adaptive technology in GPS positioning trajectory of ship navigation

Abstract This article addresses the challenges in the periodic law of high-frequency motion and effectively identifies the influence of high-frequency motion on ship dynamic positioning. The main aim of the article is to design a dynamic positioning filter by applying nonlinear adaptive technology to eliminate the disturbance to the ship’s dynamic propulsion system. This article proposes a method to control the ship’s dynamic positioning and apply nonlinear adaptive technology in the dynamic positioning control in order to obtain the ship’s state and reference coordinate system. Further, a mathematical model and a dynamic environmental model in ship dynamic positioning control are analyzed in this work. The control index model is located by the experimental data, and the control performance is improved within the allowable range. The experimental analysis revealed that if the initial position of the ship is (0, 0, 0), then the desired position is (100, 100, 0). The operating ranges of –0.6 × 107 to 0.6 × 107, –0.4 × 107 to 0.4 × 107, and –5.6 × 108 to 5.6 × 108 are used. The ranges of motion of –150 to 150, –130 to 130, and –5 to 5 are observed, respectively, along with a wind disturbance force of 8 m/s. The wave disturbance force of 1 m/s is observed along with 90° wind. It was observed from the experimentation that the ship could basically achieve a stable operation and control the environmental disturbance within the error range. The outcomes reveal that the proposed dynamic positioning model based on nonlinear adaptive technology has strong stability and accuracy.

ГЕОДЕЗІЯ, КАРТОГРАФІЯ І АЕРОФОТОЗНІМАННЯ

The aim of this work. This article is devoted to the study of geodynamic processes in the Tysza River basin within the Transcarpathian region with an analysis of geodetic observations obtained over the past decade. Method. Karst monitoring began with the identification of the most dangerous areas of the earth's surface that are subject to vertical displacements. After the detection of the most dangerous areas the local geodetic monitoring was carried out at facilities within the urban settlement to prevent possible accidents: Solotvyno, Dilove and Bila Tserkva. A collection of archival aerial photography was also used to develop a methodology for identifying changes in landscapes and landforms under the influence of geodynamic processes. Results. UAVs were used to remove karsts. On the basis of digital aerial photography data were created: orthophotos and digital terrain models. Digital aerial photography was carried out in accordance with the requirements of regulatory documents. To determine the dynamics of landslides and karst the digital aerial photography must be repeated several times at certain intervals. Aerial photography work was carried out in two stages in 2020 and 2021 Contour points were selected for identification marks. They are recognized on aerial photography and the terrain with an accuracy of at least 0.1 mm on the scale of the created plan. Mathematical processing of geodetic GPS measurements was performed using Trimble Geomatics Office software. After photogrammetric processing, the quality control of the obtained results was performed and digital surface models using DEM and TIN methods. Orthophotomaps on a scale of 1:1000 were made from raster images of aerial photographs, taking into account the created digital terrain model. There is a need for monitoring work to update information on the state of modern karst formations and areas with exogenous processes in Solotvyno and Bila Tserkva, Tyachiv district and the village Dilove, Rakhiv district, Transcarpathian region. The technology of topographic and geodetic works with the use of UAVs and GPS measurements in mountainous areas has been developed and tested. The results of aerial photography were used to visualize the study objects and to convey information regarding the deformation processes to local governments. For processes of natural or man-made nature (displacement, landslides, karst) requires the development of individual approaches to the use of UAVs. With the mass use of UAV images, a data bank is formed, which cannot be obtained by other methods. The study made it possible to create the method of complex determination of movements in exogenous and technogenic areas in mountainous areas with the use of the latest technologies. It allows quick establishing a plan-altitude basis of the required accuracy in the reference coordinate system in solving a number of applied geodesy problems using satellite technologies and UAVs for observations by objects.

Multi-Layer Fault-Tolerant Robust Filter for Integrated Navigation in Launch Inertial Coordinate System

As to an aerospace vehicle, the flight span is large and the flight environment is complex. More than that, the existing navigation algorithms cannot meet the needs to provide accurate navigation parameters for aerospace vehicles, which results in the decline of navigation accuracy. This paper proposes a multi-layer, fault-tolerant robust filtering algorithm of aerospace vehicle in the launch inertial coordinate system to address this problem. Firstly, the launch inertial coordinate system is used as the reference coordinate system for navigation calculation, and the state equation and measurement equation of the navigation system are established in this coordinate system to improve the modeling accuracy of the navigation system. On this basis, a multi-layer, fault-tolerant robust filtering algorithm is designed to estimate and compensate the unknown input in the state equation in real time and adjust the noise variance matrix in the measurement equation adaptively. Simulation results show that the errors about the integrated navigation system output parameters are reduced, through this algorithm, which improves the attitude, velocity and position estimation accuracy of the integrated navigation system. In addition, the algorithm enhances the fault tolerance and robustness of the filtering algorithm.

Additive Manufacturing In-situ and Ex-Situ Geometric Data Registration.

Recently, The number and types of measurement devices that collect data that is used to monitor Laser-Based Powder Bed Fusion of Metals processes and inspect Additive Manufacturing (AM) metal parts have increased rapidly. Each measurement device generates data in a unique coordinate system and in a unique format. Data alignment is the process of spatially aligning different datasets to a single coordinate system. It is part of a broader process called "Data Registration". This paper provides a data-registration procedure and includes an example of aligning data to a single, reference, coordinate system. Such a reference coordinate system is needed for downstream applications, including data analytic, artificial intelligence, and part qualification.

Camera Calibration for Long-Distance Photogrammetry Using Unmanned Aerial Vehicles

The traditional target-dependent camera calibration method has been widely used in close-distance and small field of view scenes. However, in view of the field coordinate measurement in the large-scale monitoring area under the complex field environment, the standard target can hardly meet the requirements of covering most of the camera’s field of view. In view of the above problem, a stereo camera calibration method is studied, using the unmanned aerial vehicles (UAV) as feature points, combined with the high-precision position information measured by the real-time kinematic (RTK) positioning system it carries. The measured UAV coordinates are unified in World Geodetic System 1984 (WGS-84). Therefore, through several preset points, the measurement reference coordinate system which is the new world coordinate system we need can be established in any monitoring area, which greatly improves the flexibility of measurement. The experimental results show that the measurement accuracy of the proposed method can reach 0.5% in the monitoring area with a diameter of 100 m. The calibration method has a wide range of application and does not need the traditional standard target, and the measurement reference coordinate system can be established according to the actual needs. It is suitable for field spatial coordinate measurement in long-distance and complex terrain environment.

On Finding a Projected Coordinate Reference System

The digital age has brought about an explosion in the growth of data, of which data with a geographical component stands out. Proper use of geographical data comes with the need for correct coordinate reference systems (CRSs). They are considered the ultimate binder for interoperability between geospatial data actors and stakeholders. Moreover, CRSs are crucial for the visual and analytical integration of geospatial data from disparate data sources. However, CRSs might be—for numerous reasons—incorrectly assigned or even missing. The result is a time-consuming study of the map, literature, and available resources to ultimately find the alleged right CRS. This study provides a summary of prevailing resources from national mapping agencies of some European countries to address the above problem. Secondly, and most importantly, is the development of an open-source Python-based software package. This software package aims to accurately estimate the best candidate CRS, given a tuple of coordinates at a priori an approximately known location. It is controlled by geocoding the known location and intersecting the resulting coordinate with the bounding box of all CRSs in the EPSG-database. An in-depth review of CRS tools by mapping authorities reveals, in particular, limitations concerning the countries’ spatial areas, in combination with often required know-how of local CRSs. To address these shortcomings, our tool is developed to enable a more generic extraction of CRSs for any given location worldwide. Testing proved successful for 30 different maps, with a grid present on the map and the CRS of the map being included in the EPSG-database.

The space quadrant and intelligent occlusion calculation methods for the external heat flux of China space Station

In the thermal control design of spacecraft and the study of its infrared radiation characteristics, the influence of external heat flux must be considered emphatically. In order to solve the complex space occlusion problem of China Space Station, the centroid ontology coordinate system is first defined as the reference coordinate system in this paper. Then, the space quadrant and intelligent occlusion calculation methods are proposed. The former is mainly to solve the shielding of the external heat flux of spacecraft body. The latter is to solve the shielding of the external heat flux of large external hangings. The results show that the maximum occlusion time is up to 6.5 min and the maximum occlusion difference is about 0.7 in the same quadrant at different solar incident angles. Moreover, if the shielding of external hangings is not considered, the time is more than 15 min when the external heat flux difference exceeds 4000 W in the sunlight area, and the maximum difference is about 6000 W. Meaningfully, the space quadrant and intelligent occlusion calculation methods proposed in this paper can effectively solve most of the occlusion problems and is suitable for various spacecraft.

Priority Analysis of Mangrove Guraping Ecotourism Development Based on Spatial Data Using Process Hierarchy Analysis

This article aims to analyze the development priorities of Guraping mangrove ecotourism based on spatial data using process hierarchy analysis (AHP). The research process is divided into three stages: the pre-processing stage, processing stage, analyzing and reporting phase. In the processing stage, the spatial data used is Landsat 8 OLI in the Guraping mangrove ecotourism area from 2013-2021 with the Coordinate Reference System World Geodetic System (WGS) 84 or Universal Transverse Mercator (UTM) Zone 52N. In the Processing stage, raster data for each zone in the Guraping mangrove ecotourism area will be calculated using the Normalized Difference Vegetation Index (NDVI) algorithm to determine the maximum, average, and minimum values value. The analyzing and reporting phase contains an idea of NDVI calculations result related to the Decree of the Minister of State for the environment in 2004. The findings of this study indicate that the ranking system in the Analytical Hierarchy Process (AHP) algorithm can be used to analyze the priority of the Guraping mangrove ecotourism development program. In AHP Calculation, the programs consist of rehabilitation, restoration, reclamation, and conservation. In addition, the alternatives are zone 1, zone 2, and zone 3. The ranking results show that the program relevant to the NDVI calculation of the Guraping mangrove ecotourism context is the rehabilitation program. Furthermore, the alternative ranking results show that Zone 1 is the priority zone for the rehabilitation program.

D-H Parameter Method-based Wearable Motion Tracking

Motion capture is a key technology for robots to accurately understand pedestrian intentions in the scene of human-machine integration. Due to the limited spatial distance and easy obstruction by obstacles, traditional optical motion capture systems often lose detection targets. This paper proposes a wearable motion tracking method based on D-H parameter method. By binding multiple wireless inertial sensor units composed of accelerometers, magnetic flux sensors and gyroscopes to various moving parts of the user’s body, accurate and robust tracking of moving targets is achieved. This method uses the known pose information of the root node to find the pose state of each level in the reference coordinate system, and establishes the human body joint rotation model and the bone position state model. The results show that the motion tracking method proposed in this paper reduces 9 degrees of freedom compared with the traditional forward kinematics method, and the algorithm efficiency is increased by about 20%, which can accurately obtain the posture characteristics of the human body. It can be seen that the D-H parameter method is reasonable for the wearable human body motion tracking.

Spatial data infrastructure (SDI) for inventory rockfalls with fragmentation information

The fragmentation phenomenon has a significant effect on rockfall risk assessment. This information is difficult to obtain, but it is key to improving rockfall modelling. For this reason, the RockModels team has gathered data on the fragmentation of several natural events since 2014 that nowadays wants to share them with professionals, academics and stakeholders. The best way for the dissemination of this information is the use of standard or data specifications in order to be interoperable. A fragmentation rockfall database has been created using all the gathered information, according to the INSPIRE Natural Hazard Area Data Specification currently in force. However, new tables have had to be added, since this specification does not consider fragmentation data. There are currently 6000 records of geometries of source areas, envelopes, deposits and mostly individual blocks. A web mapping application, with an automatic function for coordinate reference system transformation, has been created to facilitate access to the spatial database information. All that was developed on open-source software such as OpenLayers JavaScript library, database (PostGre-PostGIS) and the map generating Web Map Service (GeoServer). As more data are collected, the database can be easily updated and the new information will be published. Moreover, to improve data interpretation, a future task is to incorporate 3D models on the web application. The existence of this public database will facilitate research and advance in knowledge of this kind of natural hazards.Graphical abstractRockfall volume distribution inventory data.Georeferenced rockfall database including fragmentation data according to Technical Data Specifications of INSPIRE for natural hazards zone.Database mapping of rockfall inventory data in a WMS open access.Geometric modelling and geovisualization to fragmentation process in rockfall investigations.

Austenitic parent grain reconstruction in martensitic steel using deep learning

In this work we develop a deep convolutional architecture to estimate the prior austenite structure from observed martensite electron backscatter diffraction micrographs. A novel data augmentation strategy randomizes the global reference coordinate system which makes it possible to train our model from only four micrographs. The model is much faster than algorithmic approaches and generalizes well when applied to micrographs of a different material. Empirical evidence suggests the efficacy of the model depends on the scale of the microstructure and receptive field of the vision model. This work demonstrates that modern computer vision approaches are well suited for capturing complex spatial-orientation patterns present in orientation imaging micrographs.

Астрометрия и геодезия как одна наука. История и предназначение звездных каталогов

According to the resolution of the International Astronomical Union, since 1999 the main reference for spherical coordinates has become the international celestial reference frame ICRF, compiled from observations of quasars and point-like radio galaxies. This decision abolishes the observations necessary for compiling the traditional spherical coordinate system represented by the fundamental catalogs of the FK series. It is useful to recall the principles of astronomers of the 18th–20th centuries who had organized the determination of the absolute coordinates of stars at the state observatories, required for compiling the next fundamental catalog. This will allow natural scientists who study movements by measured coordinates of celestial objects, firstly astronomers and geodesists, to compare the opportunities provided by optical fundamental catalogs and the reference system of radio coordinates for solving the problems of their branch of science. Let us turn to historical experience, which shows that the establishment of main optical coordinate systems was not a volitional decision but was affirmed in the process of searching for the most effective method for solving both fundamental problems and satisfying current needs of each historical era.

Identify Finger Rotation Angles With ArUco Markers and Action Cameras

Abstract Measuring the motions of human hand joints is often a challenge due to the high number of degrees-of-freedom. In this study, we proposed a hand tracking system utilizing action cameras and ArUco markers to continuously measure the rotation angles of hand joints during motion. Three methods were developed to estimate the joint rotation angles. The pos-based method transforms marker positions to a reference coordinate system and extracts a hand skeleton to identify the rotation angles. Similarly, the orient-x-based method calculates the rotation angles from the transformed x-orientations of the detected markers in the reference coordinate system. In contrast, the orient-mat-based method first identifies the rotation angles in each camera coordinate system using the detected orientations and then synthesizes the results regarding each joint. Experiment results indicated that the repeatability errors with one camera regarding different marker sizes were around 2.64–27.56 deg and 0.60–2.36 deg using the marker positions and orientations, respectively. With multiple cameras employed, the joint rotation angles measured by using the three methods were compared with that measured by a goniometer. Comparison results indicated that the results of using the orient-mat-based method are more stable and efficient and can describe more types of movements. The effectiveness of this method was further verified by capturing hand movements of several participants. Therefore, it is recommended for measuring joint rotation angles in practical setups.