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Outlier/Noise-Robust Partition of Unity Implicit Surface Reconstruction
Yukie Nagai,Yutaka Ohtake,Hiromasa Suzuki,Hideo Yokota (사)한국CDE학회 2010 한국CAD/CAM학회 국제학술발표 논문집 Vol.2010 No.8
In this paper, we propose an algorithm for outlier/noise-robust surface reconstruction based on a partition of unity (PU) approach. PU based surface reconstruction is a local method that covers an area including sampling points with spherical supports of local approximations, and then generates an approximation function whose zero-level sets approximate the surface. This algorithm has many advantages including representation of fine details, and fast and memory efficient computation. Many of these advantages are realized with the locality of PU however, it is also the reason of outlier/noise-instabilities. Unfortunately, scanned data generally contain much amount of noise, and hence improving the robustness of PU based algorithm is required. We achieve an outlier/noise-robust algorithm with integrating Graph-cut and diffusion of local approximations. Since the characteristics of outliers and noise are fundamentally different, overcoming these two with different approaches is reasonable. In our algorithm, first a spherical cover of an area containing input points is generated following the PU manner. And then Graph-cut is performed in order to determine spherical supports which are considered wrongly approximating affected by outliers. Finally, the PU approximation function is updated so that its gradient field smoothed. This smoothing is based on a diffusion of the local approximations. In this paper we show the effects of this integration approach for several scanned data sets.
Variable Structure Control of Ultrasonic Motor
Tomoyoshi Takeuchi,Yutaka Nagai,Phongchai Phatpanichot 전력전자학회 1989 ICPE(ISPE)논문집 Vol.- No.-
In position control system using ultrasonic motor, the velocity of control object is controlled to approach the desired specified velocity patterns, and eventually, the position of control object is correctly at reference position This intention, here, can be success by means of variable structure control In this paper, the PI velocity feedback control is also used inside variable structure controller in order to compensate the velocity offset The design of position controller under specified velocity profiles in variable structure control's constraints is studied.
Flattening simulations of 3D thick sheets made of fiber composite materials
Morioka, Kotaro,Ohtake, Yutaka,Suzuki, Hiromasa,Nagai, Yukie,Hishida, Hiroyuki,Inagaki, Koichi,Nakamura, Takeshi,Watanabe, Fumiaki Society for Computational Design and Engineering 2015 Journal of computational design and engineering Vol.2 No.2
Recently, fiber composite materials have been attracting attention from industry because of their remarkable material characteristics, including light weight and high stiffness. However, the costs of products composed of fiber materials remain high because of the lack of effective manufacturing and designing technologies. To improve the relevant design technology, this paper proposes a novel simulation method for deforming fiber materials. Specifically, given a 3D model with constant thickness and known fiber orientation, the proposed method simulates the deformation of a model made of thick fiber-material. The method separates a 3D sheet model into two surfaces and then flattens these surfaces into two dimensional planes by a parameterization method with involves cross vector fields. The cross vector fields are generated by propagating the given fiber orientations specified at several important points on the 3D model. Integration of the cross vector fields gives parameterization with low-stretch and low-distortion.
3D scanning based mold correction for planar and cylindrical parts in aluminum die casting
Seno, Takashi,Ohtake, Yutaka,Kikuchi, Yuji,Saito, Noriaki,Suzuki, Hiromasa,Nagai, Yukie Society for Computational Design and Engineering 2015 Journal of computational design and engineering Vol.2 No.2
Aluminum die casting is an important manufacturing process for mechanical components. Die casting is known to be more accurate than other types of casting; however, post-machining is usually necessary to achieve the required accuracy. The goal of this investigation is to develop machining- free aluminum die casting. Improvement of the accuracy of planar and cylindrical parts is expected by correcting metal molds. In the proposed method, the shape of cast aluminum made with the initial metal molds is measured by 3D scanning. The 3D scan data includes information about deformations that occur during casting. Therefore, it is possible to estimate the deformation and correction amounts by comparing 3D scan data with product computer-aided design (CAD) data. We corrected planar and cylindrical parts of the CAD data for the mold. In addition, we corrected the planar part of the metal mold using the corrected mold data. The effectiveness of the proposed method is demonstrated by evaluating the accuracy improvement of the cast aluminum made with the corrected mold.
Kenichi Ohura,Akitake Makinouchi,Cristian Teodosiu,Yutaka Nagai,Jyuichi Nagse 한국소성가공학회 2010 기타자료 Vol.2010 No.6
The warpage of casting parts is a critical issue, especially for large industrial products. Besides, it is difficult to predict the warpage accurately in the casting process because of its complex dependence on mechanical and thermal factors such as the constitutive law of the high temperature metal, the temperature history of the entire part and the restrictions imposed on the deformation by the mold wall. In the present paper, a 3D finite element software V-Shrink developed within the VCAD System Research Program is used to simulate the warpage of an L-plate sand mold casting. It takes into account the thermal coupling between the cast and the mold with non-uniform heat transfer coefficient depending on the local air-gap thickness. 1) The thermo-elastoplastic constitutive law with the temperature dependency of the yield stress is used for the thermal contraction analysis. 2) The simulated warpage of the L-plate casting is in good agreement with the experimental data obtained by a 3D digitizer. Furthermore, the well-known technical finding that the inelastic strain caused by the temperature dependence of the yield stress and the local delay of the temperature drop is a dominant factor of the warpage, is confirmed by the simulation.
A system for three-dimensional gaze fixation analysis using eye tracking glasses
Ryo Takahashi,Hiromasa Suzuki,Jouh Yeong Chew,Yutaka Ohtake,Yukie Nagai,Koichi Ohtomi 한국CDE학회 2018 Journal of computational design and engineering Vol.5 No.4
Eye tracking is a technology that has quickly become a commonplace tool for evaluating package and webpage design. In such design processes, static two-dimensional images are shown on a computer screen while a subject’s gaze where he or she looks is measured via an eye tracking device. The collected gaze fixation data are then visualized and analyzed via gaze plots and heat maps. Such evaluations using two-dimensional images are often too limited to analyze gaze on three-dimensional physical objects such as products because users look at them not from a single point of view but rather from various angles. Therefore in this study we propose methods for collecting gaze fixation data for a three-dimensional model of a given product and visualizing corresponding gaze plots and heat maps also in three dimen-sions. To achieve our goals, we used a wearable eye-tracking device, i.e., eye-tracking glasses. Further, we implemented a prototype system to demonstrate its advantages in comparison with two-dimensional gaze fixation methods.