Abstract: Engineering facilities can be digitized as large-scale point-clouds by using the state-of-art mid-range laser scanners. For utilizing captured data in CAD systems, it is important to convert point-clouds to parametric surfaces. In this paper, we describe a method for robustly extract cylindrical faces and planar faces. Edges and silhouette lines have to be generated to construct bounded faces, but unfortunately points on silhouettes are very noisy in the case of mid-range laser scanners. Our method applies region-growing method on spherical space and improves the robustness. In addition, we enhance the region-growing so that surface regions can be propagated to disconnect points using multiple overlapping point-clouds.
Abstract: The contact deformation of human skin is a significant factor in the virtual ergonomic assessment of handheld products, but previous works have neglected it or dealt with it in a simple way. In this paper, we propose a physical model of the contact deformation of human skin and, based on this model, present an efficient contact solving method to simulate the physical contact of the Digital Hand with product surfaces. The realistic contact deformation effect was realized, and we experimentally verified the estimated contact area, contact force and pressure distribution, and found the estimation results by the proposed model and the contact solving method well fit with the experimental data and the past data from the literature.
Abstract: In recent years, there are a lot of active researches on nano-micro manufacturing and metrology, since not only industrial fields but also medical fields require higher accuracy with respect to miniaturizing size of the target. However, we cannot make an effective use of three dimensional measurement data for the nano-micro design and manufacturing due to a wide variety of instruments, resolutions, and noises. In fact, the nano-micro geometric modeling is at an early stage of development in spite of its importance for the next generation. In order to find a solution to this problem, we propose to combine the multi-resolution processing with the microscopic images for high speed and non-destructive geometric modeling as well as for the homogeneous modeling from micro features to macro ones. This research includes measurement data tiling between different instruments, high resolution optical microscopic imaging, focus judgment of three dimensional microscopic data, and large scale point crowd processing. These built models are potentially applied to in-line inspections and numerical simulations. Therefore, the nano-micro geometric modeling contribute to further developments of ultra precise manufacturing and the biotechnology.
Abstract: As industrial plants such as chemical and power plants continue to age, their CAD models are increasingly required for model-based planning and simulation. However, in the case of old plants, the original CAD models rarely exist, and hand-drawings do not precisely match the present states of the plants due to repeated remodeling. It is therefore becoming a common approach to reconstruct CAD models from the point cloud of such plants captured by terrestrial laser scanning and use these models for the above purposes. Such a reconstruction process is usually called “as-built modeling”. However, existing methods for as-built modeling come with such problems as the need for many human operations and computational cost. In this paper, we propose an automatic and efficient method for as-built modeling industrial plants using Manhattan-world assumption which states that there exist three dominant axes orthogonal to each other in artificial buildings and the internal parts are arranged so that they are parallel or orthogonal to one of them. In the case of industrial plants, it is reasonable to consider that long pipes and shaped steels are arranged so that they follow this assumption. In addition, plant parts are supposed to be designed as long linear sweep surfaces on CAD system or hand drawings. Our method can automatically recognize such sweep parts and their cross sectional shape which follow the assumption, as well as efficiently recognize them even from a large point cloud which may contain as many as one hundred million points in a few minutes. We demonstrate the effectiveness of our proposed method from various experiments on real scanned data.
Abstract: Spherical targets are useful for registration of point-clouds. In this paper we discuss the positioning uncertainty by laser scanners. We measured spheres of relatively large diameter from about 9m distance, and calculated their positions by the least-squares fitting. The scanning was iterated thirty times and the standard deviations of fitting result were calculated to indicate positioning uncertainty. The result shows smaller positioning uncertainty in comparison with the range noise listed in the specifications.
Abstract: Texture mapping on scanned objects, which is the method to map color images on a 3D geometric model measured by a range image sensor, is often used for constructing a realistic 3D model. Color images are affected by the illumination conditions. Therefore, discontinuities of seams occur when simply applying texture mapping. In this paper, we propose a method for correcting the discontinuities using a range intensity image. A range intensity image is a kind of intensity image that is related to the reflectance ratio of the measured points, simultaneously acquired with a range image using an active range sensor. The method estimates the color information that is not affected by the lighting environment using multiple color images and a range intensity image. As a result, the method is effective to construct a 3D model with seamless color images. The effectiveness of the correction method is illustrated by experiments with real-world objects.
Abstract: This paper describes fabrication of a magic-mirror with an extremely small concavo-convex surface, which is invisible to the naked eye. The magic-mirror was manufactured by end-milling with a machining center on the rear of the workpiece after polishing. Incident light was radiated to the mirror surface and the reflected light was projected on a screen. The tool pass by CNC programming show up as image of magic-mirror on the screen. Analysis of the image on the screen indicated completion rate of magic-mirror surface generation. As some experimental result, the integrated magic-mirror production process on the machining center could be achieved by a novel application of on-machine magnetic abrasive finishing and ball end-milling. Moreover, it was found to possible to fabricate a magic-mirror with satiny and continuous-curvature corrugated surface.
Abstract: The aims of this study were to fabricate biopolymer and biocomposite scaffolds for bone tissue engineering by an air pressure-aided deposition system. A thermosensitive mPEG-PCL-mPEG triblock copolymer was synthesized as a biopolymer material. Biocomposite material was composed of synthesized biopolymer and hydroxyapatite (HA) with a mean diameter of 100 µm. The weight ratio of HA added to the synthesized biopolymer was 0.5. The experimental results show that the average compressive strength of biocomposite scaffolds with mean pore size of 410µm (porosity 81%) is 18.38 MPa which is two times stronger than that of biopolymer scaffolds.
Abstract: Generally, ball end mills are used for free-form surface machining. When machining curved surfaces with large curvature change using ball end mills, it is necessary to use tools with larger curvature of the cutting edges than the maximum curvature of the surface and minute pick feeds or to change tools for fitting the curvature of one part of the surface. However this causes poor machining efficiency. The curvature of the cutting edge of a flat end mill can be fitted to the curvature of a point on machined surfaces by adjusting the tool posture. Therefore, flat end mills can efficiently cut almost all curvature curved surfaces without tool change. This paper proposes two methods for deciding tool posture and tool path for 5-axis control machining based on minimum cusp height. To decide the tool path, one method defines tool paths along isoparametric curved lines, while the other defines tool paths along curved lines along the minimum curvature direction. The basic system was constructed based on the proposed method, and the effectiveness of the proposed method was verified.
Abstract: Machining is often performed by a machining center using various cutting tools and conditions for different shapes and materials. Recent improvements in CAM system make it easier for even unskilled engineers to generate NC programs. In the NC program, the end-milling conditions are decided by engineers. However, engineers need to decide the order of the process, cutting tool selection, and the end-milling conditions on the basis of their expertise and background knowledge because the CAM system cannot automatically decide. Data-mining methods were used to support decisions about end-milling conditions. Our aim was to extract new knowledge by applying data-mining techniques to a tool catalog. We used both hierarchical and non-hierarchical clustering of catalog data and also used applied multiple regression analysis. We focused on the shape element of catalog data and we visually grouped ball end-mills from the viewpoint of tool shape, which here meant the ratio of dimensions, by using the k-means method. We also found an expression for calculating end-milling conditions, and we compared the calculated with the catalog values.