Datum Plane Research Articles

A generalized framework for identification and geometrical feature extraction of circular and polygonal shaped prisms

Abstract This paper introduces a versatile framework crucial for robotic applications such as object manipulation, mobile robot navigation, and pole climbing. It addresses the identification of geometric shapes and dimensions of diverse objects found in varied environments. The proposed method utilizes LiDAR scanning to capture objects from different angles, generating point clouds merged through transformations and superimpositions. After filtering and slicing, intersections are isolated and projected onto a chosen datum plane. The framework employs Non-Linear Least Square fitting via Gauss Newton iterative approach, utilizing pseudo-inverse Jacobian of a hypotrochoid to approximate polygons. The algorithm consecutively fits polygon prisms, determining the best fit with the least norm of error. Results indicate an average least square error of less than 9% for radius fitting and a high f-score for shape identification.

Creation of Engineering Drawing Learning Modules Using Datum Plane Media in Improving Students' Competence in Automotive Engineering Skills at SMK Negeri 55 Jakarta

The aim of this research is to determine the feasibility and effectiveness of the engineering drawing module using datum plane media to strengthen students' knowledge about projections on objects. This research uses the 4D research method developed by S. Thiagarajan, Dorothy S. Semmel, and Melvyn I. Semmel in 1974 which consists of 4 stages, namely Define, Design, Develop and Disseminate. Data was collected through interviews, questionnaires and pre test-post test. The subjects of this research were students majoring in automotive engineering at SMKN 55 Jakarta 2023/2024 academic year class x semester 1 with a sample size of 30 students from a population of 3 classes totalling 103 students. The research began with Define, namely defining the need for difficulties in students' understanding of reading and drawing projections by observing and interviewing teachers who teach technical drawing. Furthermore, from the observation data obtained, the researchers looked for solutions to the problems faced by automotive vocational school students with modules that use datum planes, so the researchers designed the required modules and datum planes. At the Develop stage, the researcher's design is validated by material experts and media experts, their criticism and suggestions are used as input for revising the media created. Finally, the Disseminate media stage, which had been validated and revised, was used on 30 students from SMKN 55 Jakarta, carried out a pre-test-post test and obtained an average result for the entire pre-test sample of 45.33 and post-test of 68.17.

A Novel High-Fidelity Simulation for Finishing Operations: Hybrid Image Mosaic and Wavelet Decomposition.

In finishing simulations, achieving accurate results can be challenging due to the minimal amount of material removal and the limited measurement range of surface micro-topography instruments. To overcome these limitations, a novel high-fidelity modeling method combining image mosaic and wavelet decomposition technologies is proposed in this paper. We achieve the stitching of narrow field and high pixel micro morphology images through four steps: image feature extraction, overlapped feature matching, feature fusion, and stitching effect evaluation. On this basis, the wavelet decomposition method is employed to separate detection signals based on their respective frequencies, allowing the establishment of a datum plane and a roughness surface. The point cloud model undergoes a transformation into a continuous geometric model via the Poisson reconstruction algorithm. In the case study, four sample images of an aluminum alloy sheet after barrel finishing were collected using the ZeGage Plus optical profiler. Each image has an actual size of 834.37 μm × 834.37 μm. Subsequently, a comparison was carried out between the physical and simulation experiments. The results clearly indicate that the proposed method has the potential to enhance the accuracy of the finishing simulation by over 30%. The error between the resulting model and the actual surface of the part can be controlled within 1 μm.

Online Recognition of Fallen-Off Bond Wires in IGBT Modules.

As a core component of power conversion systems, insulated gate bipolar transistor (IGBT) modules continually suffer from severe thermal damage caused by temperature swings and shear stress, resulting in fatigue failure. Bond wires falling off is one of the failure modes of IGBT modules. Given that the number of fallen-off bond wires is a significant parameter to evaluate the health status of the IGBT modules, this paper proposes an online identification model to recognize the number of fallen-off bond wires during normal operation. Firstly, a database containing datum Vce,on-Tj-IC (collector-emitter on-state voltage Vce,on, chip junction temperature Tj, collector current IC) planes with different fallen-off bond wires is built based on an offline aging test. Secondly, a Foster network model and a special circuit are designed to measure the junction temperature Tj and the collector-emitter on-state voltage Vce,on, respectively. Thirdly, the feature points of the IGBT module represented by Vce,on, Tj, and IC are given to the database to recognize the number of fallen-off bond wires according to the position of the feature points in the datum plane. The experimental results show that the proposed method can determine the fallen-off bond wires under the operation condition.

3-D Reconstruction and Measurement of Blade Profiles With Laser-Scanning Sensor via Multiview Registration Based on Dynamic Encoding of Feature-Coordinate Information

Currently, optical-based method provides a feasible means for blade reconstruction and measurement. However, as the key step, multi-view registration is still heavily reliant on the measurement system's motion stability and geometric accuracy. Moreover, the complex and high-reflective freeform surface of blades may result in both insufficient overlaps and less prominent overlap-area features between adjacent views, making accurate multi-view data alignment difficult. Thus, we propose a method to realize accurate 3-D reconstruction and measurement of blade profiles based on a scanning system with a laser-sensor and a coarse-to-fine registration strategy. Firstly, coarse alignment of the multi-view data is achieved by calibrating the system's rotational axis using the blade datum plane feature, which can provide a good initial value for the fine registration and improve the reconstruction efficiency. Then, a fine registration algorithm based on the dynamic encoding of feature-coordinate fusion information is proposed to refine the coarsely aligned data and reduce the effect of system motion error on registration accuracy. Here, the introduction of fusion information can effectively eliminate the redundant correspondences to continuously optimize the matching probability between multi-view data in each iteration, improving registration accuracy and efficiency. Finally, experiments on typical blades and comparison with the other fine registration algorithms demonstrate the accuracy and robustness of the proposed method.

Research on Deformation Monitoring of Invert Uplifts in Soft Rock Tunnels Based on 3D Laser Scanning

The soft surrounding rock in tunnels has the characteristics of low strength, easy softening after soaking, and poor self-stability, which makes the inverted arch structure in soft rock tunnels prone to uplift deformations. Therefore, a deformation monitoring method for inverted arch uplifts of soft rock tunnels based on 3D laser scanning technology is studied to improve deformation monitoring. A Leica Scan Station2 3D laser scanner is used to collect 3D point cloud data of soft rock tunnel inverts. Using the automatic matching method of public landmarks and the improved Rodrigues parameter method, the collected 3D point cloud data are spliced and through the Mallat algorithm, the 3D point cloud data are reconstructed and processed after splicing. The whole least square method is used to fit the reconstructed 3D point cloud data. Through the principal component analysis method, the normal vector of the fitting plane is estimated and the best datum plane of the soft rock tunnel invert is found. By calculating and extracting the geometric parameters of the slice point cloud, the monitoring of inverted arch uplift deformations in soft rock tunnels is completed. The experiment shows that this method can effectively collect 3D point cloud data of soft rock tunnel inverts, and complete point cloud stitching and reconstruction. This method can effectively monitor the uplift deformation of inverted arches at different grouting depths.

Trajectory tracking control of unmanned surface vehicle based on exponential global fast terminal sliding mode control

This article studies the trajectory tracking of an underactuated unmanned surface vehicle. The trajectory tracking controller is divided into two parts: the kinematics controller and the dynamic controller. Taking the hull coordinate system of the unmanned surface vehicle as the datum plane, the kinematics controller is designed based on the backstepping method, and the virtual control input of the speed and the heading deviation of the ship are obtained. A dynamic controller is designed through an exponential sliding surface to stabilize the error of speed and heading deviation, thereby stabilizing the position error. In the process of designing the controller, the stability of the entire closed-loop control system is analyzed using Lyapunov stability theory. Finally, the designed numerical simulation experiment is carried out. The proposed exponential sliding mode controller is compared with the global integral sliding mode controller, and it is verified that the proposed controller has better effectiveness and robustness in the trajectory tracking of the underactuated unmanned surface vehicle.

Three-Dimensional Method Combining Linearly Structured Light Sensing and Rotary Scanning for Measuring Aviation Bearings

The geometric parameters of aviation bearings need to be accurately measured to ensure that the bearings are correctly assembled for reliable operation and quality purposes. This study aimed to solve the problems presented by the low accuracy and low efficiency of the existing method while avoiding the error introduced by the deviation of the measurement beam from the center of the aviation bearings during measurement. This method determines the spatial posture of the axis of the rotary table using linear structured light sensing, and extracts the spatial point-cloud data of the aviation bearings based on rotary scanning. We propose algorithms for spatial property determination and point-cloud segmentation. To avoid the error caused by the deviation of the measurement beam from the center of the aviation bearings, the point-cloud data are transformed to a new coordinate system prior to extracting the features of the datum plane and raceway. An aviation bearing is measured to verify the validity of the proposed method. The radius and eccentricity of the raceway are 4.900 mm and 0.010 mm with experimental standard deviations of 0.002 mm and 0.001 mm, respectively. For comparison purposes, experiments with a coordinate measuring machine and contourgraph were also performed. The expanded measurement uncertainty considering the repeatability, reference instruments, and temperature drift is 1.6 μ m. The proposed method can be extended to precision noncontact measurements of workpieces with rotary structures.

Calibration method for a structured light system based on DIC.

Structured light is a non-contact three-dimensional shape measurement method. The structured light system based on diffractive optical elements (DOEs) is widely used due to its low cost and compact structure. However, compared with a time sequence coded structured light system based on a digital projector, its projector cannot change the content, so it cannot be calibrated with a phase-shift-based method. This paper proposes a calibration method based on the pseudo-camera method and digital image correlation (DIC). It is suitable not only for the calibration of systems based on time series coding but also for the calibration of a speckle structured light system based on DOEs. Validation experiments were conducted in which our method achieved a reprojection error of 0.68 pixels in calibration and a radius error of less than 1% in a measurement of a cylinder in a 20cm×10cm field. Compared with existing calibration methods, this method does not need to set a datum plane, takes fewer photos, operates simply, and has higher calibration efficiency.

Optimized design and key performance factors of a gas circulation filtration system in a metal 3D printer

To further improve the quality of parts in metal 3D printers, it is necessary to optimize the structure and study the performance of their gas circulation filtration systems. First, we used the parametric modeling method to complete the formed cavity modeling. We then optimized the design of the air inlet structure of the formed cavity using the moldflow simulation method, and finally, we evaluated the optimized design results through assembly experiments and measurements of the molded parts’ components. The combination of parametric modeling and moldflow simulation methods produced a high modeling efficiency and had a good effect on the optimized design of the gas circulation filtration systems. After optimizing the design, the turbulence intensities and distribution areas of the formed cavities were reduced. During the 3D printing of the curved guide plate, the plane of the guide plate holder was inclined 55° relative to the machining datum plane, which improved the form quality. The 3D printed curved guide plate closely matched the inlet end of the printer’s air duct, and the upper guide plate was fixed at a suitable position using screws. The niobium contents of the parts formed by the guide plate in Design 2 were low, which lays a foundation for the 3D printing of high-performance metal parts.

Theoretical model and its experimental verification on nonlinear flow through a rough fracture of silty mudstone under low water head

An important method to study the seepage characteristics of rock fractures is using nonlinear flow models. However, existing nonlinear flow models are unable to describe the flow law of water-soil particles mixture through the rough fractures of soft rock because the rheological properties of the fluid are rarely considered. In this study, a novel nonlinear flow model (WST model) for water-soil particles mixture through rough fracture of silty mudstone under low water head was proposed based on local viscous pressure drops and local pressure drops. To verify the accuracy of the model, saturated seepage experiments were carried out on five silty mudstone samples with a rough fracture under low water head. The results demonstrate that compared with the MT model (a nonlinear flow model for fluid flowing though rough rock fracture at a low velocity), the WST model is preferable to fit experimental data, showing better precision in describing nonlinear flow through rough fracture of silty mudstone under low water head conditions. Furthermore, the WST model is particularly applicable when the average height of the surface of all fracture units relative to the datum plane is less than 0.62 mm and the Reynolds number is less than 620. In addition, the disordered movement of soil particles under the combined action of inertia and water head is the main reason for the nonlinear flow of water–solid particles mixture in the silty mudstone fracture.

A New assembly precision prediction method of aeroengine high-pressure rotor system considering manufacturing error and deformation of parts

The accurate prediction of high-pressure rotor system assembly precision before assembly is the premise of improving aeroengine assembly quality and performance. The existing assembly precision prediction models (APPM) only consider the manufacturing error factors of parts, but rarely involve the deformation of parts under load, so there is a certain gap between the prediction results and the actual situation. This article studies the construction method of APPM considering the manufacturing error and deformation factors of parts. Firstly, the fitting algorithm is used to obtain the fitting deformation surface(FDS) of each mating surface under load, which provides the basis for constructing assembly error model considering manufacturing error and deformation of parts; secondly, according to the relative position relationship between the FDS and the datum plane, the error model of each mating surface of the assembly is effectively constructed by the small displacement torsor theory; thirdly, according to the different errors of each fitting end face, a prediction model of assembly precision for two rough surfaces is constructed by homogeneous coordinate transformation method; finally, a high-pressure compressor rotor system is used as an example to verify the effectiveness of the precision prediction model. The results show that the prediction results based on the proposed model are closer to the actual conditions. This paper provides an effective prediction model for high-pressure rotor system assembly precision, and has important application value for improving the assembly quality and performance of aeroengine.

Stability of Contact Discontinuity with General Perturbation for the Compressible Navier-Stokes Equations with Reaction Diffusion

In this article,for the compressible Navier-Stokes equations which have reaction diffusion, the stability of contact discontinuities is considered. The new characteristic for the flow is appearance of the divergence between energy gained and lost because of the reaction . In the energy equations,the term related to the mass fraction of the reactant leads to new technical problem. To solve this problem, in terms of the solutions,a new system should be set up. Using the anti-derivative method and the elaborated energy method, we obtain that as long as the general perturbation of the initial datum plane and the strength of the contact wave are properly small, the contact wave is nonlinear and stable. As a byproduct, we can establish the convergence velocity of contact wave.

Optical Measurement Method for Blade Profiles Based on Blade Self-Features

Developing accurate and efficient measurement systems for blade profiles has always been a vital issue in blade manufacturing. Nowadays, optical-based systems for measuring blade profiles have attracted significant interest due to their high efficiency and flexibility. However, as key steps in optical measurement of blades, system calibration and establishment of measurement datum are normally accomplished based on calibration objects, which may introduce uncertainty and affect the accuracy of the measurement. In this article, we propose a novel method for blade-profile measurement based on blade self-features. A measurement system based on a four-axis platform and laser scanning sensor (LSS) is developed. A calibration method based on the blade datum plane feature is introduced to eliminate the pose error of the system without using additional calibration objects. A feature-matching algorithm based on the covariance matrix of the blade local leading-edge feature is further proposed to establish the measurement datum. The proposed method requires smaller system-motion space and fewer LSS viewpoints, which would improve the efficiency and flexibility of the measurement system. Furthermore, less error accumulation can be achieved using our method, thus, resulting in higher measurement accuracy. The experimental results reveal the feasibility and good practical application prospect of this method.

Effects of defects on the interfacial shear characteristics between graphene and poly (methyl methacrylate)

AbstractPullout simulations were conducted to investigate the interfacial shear properties between defective graphene (DGr) and polymethyl methacrylate (PMMA) through molecular dynamics simulations with ReaxFF reactive force fields. The effects of number of defects (Stone‐Wales [SW] and double‐vacancy [DV] defects) were investigated. Our results showed that these two types of defects can obviously enhance the interfacial shear strengths of DGr /PMMA nanocomposites. And the DV defects have a greater contribution to the interfacial shear strength enhancement compared to the SW defects. Analysis of the morphology of DGr indicated that surface roughness, which was induced by defects, plays an important role in enhancing the interfacial shear strength at the interface between the DGr and PMMA. Moreover, the effects of chemical functionalization at the defect sites were also investigated. We observed that the CO bonds of functional groups (hydroxyls) at defect sites inclined from the datum plane (z = 0 plane) of the graphene sheet. The inclination of CO bonds, which weakened the mechanical interlocking between functional graphene and PMMA matrix, differently influenced by the DV defect and SW defect.

Preliminary tephrochronological study of the Yezo Group (uppermost Albian–basal Campanian) in north Japan

The Yezo Group, exposed in north Japan, is a Cretaceous siliciclastic marine sequence accumulated in the active Asian continental margin of the northwest Pacific. This group is regarded as an important Cretaceous reference sequence in Japan because the detailed age of the group has been determined by numerous studies of bio- and chemostratigraphies, in addition to the radiometric dating of tuffs. Here we preliminarily establish a tephrostratigraphy in the middle–upper parts of the Yezo Group (uppermost Albian–basal Campanian interval) based on the trace-element composition of apatite contained in tuffs to improve the regional stratigraphic correlation of the Cretaceous sequences in the northwest Pacific region. The results demonstrate that the Cl, Mg, Mn, Fe, Y and Ce contents of apatite are useful to discriminate and correlate individual tuffs in the Yezo Group. The correlation of tuffs among distant areas in Hokkaido, Japan revealed three widely traceable (within a distance of several hundreds of kilometers) tuffs intercalated in the lower Cenomanian, Turonian/Coniacian boundary and the Santonian/Campanian boundary. Correlation of the tuffs also solves the local biostratigraphic problem where the datum plane of age-diagnostic fossils is sometimes diachronous across areas, which is attributed to the sporadic occurrences of fossils and/or different depositional settings.

A Normal Sensor Calibration Method Based on an Extended Kalman Filter for Robotic Drilling.

To enhance the perpendicularity accuracy in the robotic drilling system, a normal sensor calibration method is proposed to identify the errors of the zero point and laser beam direction of laser displacement sensors simultaneously. The procedure of normal adjustment of the robotic drilling system is introduced firstly. Next the measurement model of the zero point and laser beam direction on a datum plane is constructed based on the principle of the distance measurement for laser displacement sensors. An extended Kalman filter algorithm is used to identify the sensor errors. Then the surface normal measurement and attitude adjustments are presented to ensure that the axis of the drill bit coincides with the normal at drilling point. Finally, simulations are conducted to study the performance of the proposed calibration method and experiments are carried out on a robotic drilling system. The simulation and experimental results show that the perpendicularity of the hole is within 0.2°. They also demonstrate that the proposed calibration method has high accuracy of parameter identification and lays a basis for high-precision perpendicularity accuracy of drilling in the robotic drilling system.

On-sate calibration method of target distance of the sky screen target velocity measuring system

For the projectile velocity accuracy problem of sky screen target velocity measurement system under the condition of shooting range test site environment, a calibration method of the target distance parameter of sky screen target velocity measuring system is proposed in this paper. According to the characteristics of the screen of sky screen target, reference plane and distance measuring datum plane components are designed, which include laser plane projection apparatus, plane normal laser projector, high precision laser rangefinder, precision platform and tripod. The target distance parameter calibration is completed cooperate with theodolite and precision optical instruments, etc. The standard uncertainty and synthesis of uncertainty of various parameters are evaluated. The expanded uncertainty of measuring target distance of 3000 mm is 1.4 mm. The gas bullets live-fire test verifies the feasibility and correctness of the calibration method.

Mesoscopic Weakening Feature of Marble During Water Rock Interaction

Research on the water–rock interaction has become an important subject in rock mechanics field, the link between the mineral particles is weakened and the microstructure of rock mass is changed because of chemical corrosion effect after water–rock interaction. In this paper, double torsion testing of marble specimens has been adopt to determine subcritical crack propagation parameters during rock interaction, the morphological characteristics in this process were also quantified while the surface was scanned by a three-dimensional high-accuracy non-contact laser morphology instrument Talysurf CLI 2000. It shows the discreteness and deviation degree of datum plane on the surface of the rock specimens are increased after water–rock interaction, the highness difference decreased and become more coordinated. Meanwhile, the corresponding relationship between stress intensity factor KI and subcritical crack growth velocity v shows that rock interaction speeds up the subcritical crack growth. Those testing results provide a basis for the micro damage mechanism studying for rock engineering stability which are related to hydrochemistry.

Reverse Engineering of CFETR Vacuum Vessel Mockup

The 1/32 subsector of China Fusion Engineering Test Reactor vacuum vessel mockup is fully penetration welded together with four poloidal segments (PSs) which are made by forming and welding, so that each PS needs to machine the welding grooves. However, the measurement results show that there are dimensional errors between the design model and each PS which has been made. This means that the welding grooves cannot be machined directly according to the design model. So, the method of reverse engineering is used to achieve the 3-D model of each PS which has been made. Based on this 3-D model, the model for CNC machining can be designed. At the same time, the machining equipment for PS is a three-coordinate CNC floor-type milling and boring machine which needs a datum plane when it is milling. Considering each PS has a complex surface profile, 3-D datum transformation is used for solving the problem of lacking the machining benchmark. At present, based on these two methods, the machining work of welding grooves for eight PSs has been completed which has met the requirements of assembly and welding.