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geometric approaches for reducing burr formation in planar milling by avoiding tool exits

Journal of Manufacturing Processes 2005年第2期7卷 182-195页

作者： Chu, Chih-Hsing Dornfeld, David Dept. of Industrial Engineering and Engineering Management National Tsing-Hua University Hsinchu Taiwan Laboratory for Manufacturing Automation Dept. of Mechanical Engineering University of California at Berkeley Berkeley CA United States

One of the most effective methods for reducing milling exit burrs is to prevent the tool from exiting the workpiece. Exit here refers the condition in which a cutting edge is moving out of the workpiece while removing material. Only entrance burrs can occur under this circumstance, which are usually considered burr-free. This study proposes a set of geometric algorithms for avoiding tool exits in planar milling. Two distinct approaches are developed for tool path planning of 2-D polygons. The first approach generates exit-free tool paths by offsetting the workpiece edges with appropriate widths of cut. The second one adjusts tool positions locally on given tool paths. In addition, a two-stage algorithm is designed for 2-D free-form contours. The cutter locations causing the tool to exit the workpiece are first detected;then a heuristic scheme is applied to generate new cutter locations with no tool exits. Experimental results show that edge quality is significantly improved using the proposed methods. This work provides a feasible way for suppressing burr formation in an automatic manner, and thus reduces the need for deburring.

关键词： Burr Formation Edge Finishing geometric algorithm Planar Milling Tool Exit

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Precise Hausdorff distance computation between polygonal meshes

Precise Hausdorff distance computation between polygonal mes...

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Conference on Geometry - Theory and Applications

作者： Barton, Michael Hanniel, Iddo Elber, Gershon Kim, Myung-Soo Technion Israel Inst Technol IL-32000 Haifa Israel SolidWorks Corp Concord MA 01742 USA Seoul Natl Univ Seoul 151744 South Korea

We present an exact algorithm for computing the precise Hausdorff distance between two general polyhedra represented as triangular meshes. The locus of candidate points, events where the Hausdorff distance may occur, is fully classified. These events include simple cases where foot points of vertices are examined as well as more complicated cases where extreme distance evaluation is needed on the intersection curve of one mesh with the medial axis of the other mesh. No explicit reconstruction of the medial axis is conducted and only bisectors of pairs of primitives (i.e. vertex, edge, or face) are analytically constructed and intersected with the other mesh, yielding a set of conic segments. For each conic segment, the distance functions to all primitives are constructed and the maximum value of their low envelope function may correspond to a candidate point for the Hausdorff distance. The algorithm is fully implemented and several experimental results are also presented. (C) 2010 Elsevier B.V. All rights reserved.

关键词： Hausdorff distance Polygonal mesh geometric algorithm Bisector surface Medial axis Low envelope

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Finding efficient robot path for the complete coverage of a known space

Finding efficient robot path for the complete coverage of a ...

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IEEE/RSJ International Conference on Intelligent Robots and Systems

作者： Yao, Zhiyang Chinese Univ Hong Kong Dept Automat & Comp Aided Engn Hong Kong Hong Kong Peoples R China

ISBN: (纸本)9781424402588

In robot planning problems, the complete coverage path planning refers to the problem of determining a path that a robot must take in order to pass over each point in an environment and avoid obstacles. Applications include demining, sweeping, cleaning, vacuuming, inspection robots. For this kind of problem, not only the complete coverage should be performed, but an efficient path is highly desired. Using traditional sweeping line strategy often requires several relocation moves, leading to poor efficiency. In this paper we describe a geometric algorithm for generating paths by using a modified sweeping line strategy that attempts to minimize extra relocation moves. Several examples are used in the paper to show the advantage of our algorithm over traditional approaches.

关键词： geometric algorithm path planning complete coverage problem

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Universal Reconfiguration of Facet-Connected Modular Robots by Pivots: The O(1) Musketeers 27

Universal Reconfiguration of Facet-Connected Modular Robots ...

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27th Annual European Symposium on algorithms (ESA)

作者： Akitaya, Hugo A. Damian, Mirela Dujmovic, Vida Korman, Matias Parada, Irene Sacristan, Vera Arkin, Esther M. Demaine, Erik D. Flatland, Robin Palop, Belen van Renssen, Andre Tufts Univ Medford MA 02155 USA Villanova Univ Villanova PA 19085 USA Univ Ottawa Ottawa ON Canada Graz Univ Technol Graz Austria Univ Politecn Cataluna Barcelona Spain SUNY Stony Brook Stony Brook NY 11794 USA MIT 77 Massachusetts Ave Cambridge MA 02139 USA Siena Coll Loudonville NY USA Univ Valladolid Valladolid Spain Univ Sydney Sydney NSW Australia

ISBN: (纸本)9783959771245

We present the first universal reconfiguration algorithm for transforming a modular robot between any two facet-connected square-grid configurations using pivot moves. More precisely, we show that five extra "helper" modules ("musketeers") suffice to reconfigure the remaining n modules between any two given configurations. Our algorithm uses O(n(2)) pivot moves, which is worst-case optimal. Previous reconfiguration algorithms either require less restrictive "sliding" moves, do not preserve facet-connectivity, or for the setting we consider, could only handle a small subset of configurations defined by a local forbidden pattern. Configurations with the forbidden pattern do have disconnected reconfiguration graphs (discrete configuration spaces), and indeed we show that they can have an exponential number of connected components. But forbidding the local pattern throughout the configuration is far from necessary, as we show that just a constant number of added modules (placed to be freely reconfigurable) suffice for universal reconfigurability. We also classify three different models of natural pivot moves that preserve facet-connectivity, and show separations between these models.

关键词： Reconfiguration geometric algorithm pivoting squares modular robots

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WIRE ELECTRICAL DISCHARGE MACHINING (WEDM) AS A SUBTRACTIVE RAPID MANUFACTURING TOOL

WIRE ELECTRICAL DISCHARGE MACHINING (WEDM) AS A SUBTRACTIVE ...

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作者： Yang, Zhi PennState University Libraries

学位级别：Doctor of Philosophy

A modern Wire Electrical Discharge Machining (WEDM) system is capable of producing more complex geometry than 2D, 2½D or ruled surface parts. The improved geometric capability and the other well-known advantages, such as capability of cutting hard materials, ignorable cutting force, make WEDM a potential Rapid Prototyping (RP) process. Unfortunately, limited capability in process planning automation for six-axis WEDM requires significant process planning time and *** research presents the development of a methodology and the associated algorithms for using WEDM as a subtractive rapid prototyping process. Specifically, an automatic process planning system is built for six-axis WEDM process. A boundary representation is used to model part geometry and the manufacturability of a part on a six-axis WEDM machine is addressed in this research as well. In particular, a stereolithography (STL) file is used as the input for the algorithms. Global tangent visibility, fabrication orientation, and the setup requirements and numerical control code are the *** to the importance of visibility analysis in the automation of the milling process planning, global tangent visibility analysis is the foundation in the automation of WEDM process planning. In this research, an algorithm to calculate the global tangent visibility for polyhedral computer-aided design (CAD) models was developed. A greedy algorithm is also developed to classify the global visibility results and to determine the setup plans for producible geometries on six-axis WEDM. Number of setup orientations is determined automatically for six-axis WEDM machines. A method to generate machine instructions automatically based on tangent visibility results and setup plans was also developed. In order to verify the methodology, a verification system is built; and several sample parts are fabricated. The methodology and algorithms developed in this research result in a systematic automatic process planning meth

关键词： Visibility Analysis Wire EDM Computer-aided Manufacturing Rapid Manufacturing Process Planning geometric algorithm

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Independent component analysis based on scatter diagram

Independent component analysis based on scatter diagram

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International Conference on Optical Sensing and Nanotechnology (ICOSN 99)

作者： Hirokawa, K Yamaguchi, T Itoh, K Eastern Hiroshima Prefecture Ind Res Inst Fukuyama Hiroshima 7210974 Japan

ISBN: (纸本)0819432148

We propose a novel algorithm far the independent component analysis that reshapes a scatter diagram or the joint probability density function of the pixel values of the mixed signals. The detailed procedure of the algorithm is described and its performance is numerically evaluated. The present algorithm geometrically separates original independent images from mixed images by the linear transformation, in which shift, shearing and rotation are performed to the scatter diagram. After the transformations and normalizations, the basis vectors of the independent signal become orthogonal and match the coordinates. In the implementation, it is shown that the algorithm can decompose two independent images from two mixed images. In additions, the proposed algorithm are compared to two conventional algorithms;[G. Burel: Neural Networks 5, 937 (1992)] and [A. Hyvarinen and E. Oja: Neural Comp. 9, 1483 (1997)], in calculation speed and extraction accuracy.

关键词： independent component analysis geometric algorithm signal processing signal mixture blind signal separation scatter diagram

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Photogrammetry-based computational fluid dynamics

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COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING 2023年第PartB期417卷

作者： Wang, Xuguang Jaiswal, Monu Corpuz, Ashton M. Paudel, Shashwot Balu, Aditya Krishnamurthy, Adarsh Yan, Jinhui Hsu, Ming -Chen Univ Illinois Urbana & Champaign Dept Civil & Environm Engn 205 N Mathews Ave Urbana IL 61801 USA Iowa State Univ Dept Mech Engn 2043 Black Engn Ames IA 50011 USA

Computational fluid dynamics (CFD) is the cornerstone of the design and analysis process in many engineering applications. Not only has it been applied in the design phase, but it has also been employed for analyzing the fluid flow phenomena during the operation phase for many in-use structures, such as vehicles, buildings, and landscapes. However, creating a 3D mesh-based model of in-use structures that can be used by conventional boundary-fitted CFD methods is labor-intensive, time-consuming, and sometimes impossible. Due to the challenges introduced by geometry complexity and lack of design information, it is often difficult to perform an accurate and efficient CFD analysis of these objects. This paper aims to overcome such challenges by proposing a novel photogrammetry-based CFD framework for simulating in-use structures whose design models and analysis meshes are hard to obtain. The proposed framework integrates machine learning-based 3D point cloud reconstruction of structures from 2D images obtained from portable devices (e.g., cell phones and drones) and an immersogeometric approach that can carry out flow analysis directly on reconstructed point clouds. We first present the technical details of point cloud reconstruction techniques and the immersogeometric analysis method. We then simulate the flow past a standard 12 oz soda can reconstructed using photogrammetry and compare the results with reference solutions to assess the accuracy of the approach. Finally, the proposed photogrammetry-based CFD is applied to simulations of a bell tower and the Kavita and Lalit Bahl Smart Bridge on the University of Illinois Urbana-Champaign (UIUC) campus to demonstrate the robustness of the framework and its applicability to real-world in-use civil structures.(c) 2023 Elsevier B.V. All rights reserved.

关键词： Photogrammetry Point cloud reconstruction geometric algorithm Deep learning Computational fluid dynamics Immersed method

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algorithmic approach to geometric solution of generalized Paden-Kahan subproblem and its extension

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INTERNATIONAL JOURNAL OF ADVANCED ROBOTIC SYSTEMS 2018年第1期15卷

作者： Dimovski, Igor Trompeska, Mirjana Samak, Samoil Dukovski, Vladimir Cvetkoska, Dijana Inst Adv Composites & Robot Prilep Macedonia SS Cyril & Methodius Univ Skopje Fac Mech Engn Skopje Macedonia

Kinematics as a science of geometry of motion describes motion by means of position, orientation, and their time derivatives. The focus of this article aims screw theory approach for the solution of inverse kinematics problem. The kinematic elements are mathematically assembled through screw theory by using only the base, tool, and workpiece coordinate systemsopposite to conventional Denavit-Hartenberg approach, where at least n + 1 coordinate frames are needed for a robot manipulator with n joints. The inverse kinematics solution in Denavit-Hartenberg convention is implicit. Instead, explicit solutions to inverse kinematics using the Paden-Kahan subproblems could be expressed. This article gives step-by-step application of geometric algorithm for the solution of all the cases of Paden-Kahan subproblem 2 and some extension of that subproblem based on subproblem 2. The algorithm described here covers all of the cases that can appear in the generalized subproblem 2 definition, which makes it applicable for multiple movement configurations. The extended subproblem is used to solve inverse kinematics of a manipulator that cannot be solved using only three basic Paden-Kahan subproblems, as they are originally formulated. Instead, here is provided solution for the case of three subsequent rotations, where last two axes are parallel and the first one does not lie in the same plane with neither of the other axes. Since the inverse kinematics problem may have no solution, unique solution, or many solutions, this article gives a thorough discussion about the necessary conditions for the existence and number of solutions.

关键词： Screw motion Paden-Kahan subproblem geometric algorithm inverse kinematics mathematical foundations

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Research on the faulty treatment of cascaded Hbridge inverter under neutral shift

Research on the faulty treatment of cascaded Hbridge inverte...

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2012 International Conference on Power Electronics Engineering and Computer Technology(PEECT 2012)

作者： Ren Lei Shouzhi Li Hao Wang Department of Electrical Engineering Xi'an University of Technology The Professor of Department of Electrical Engineering Xi'an University of Technology Xi'an jiaotong University

Neutral shift can effectively use the remaining normal unit to increase the output voltage value,but the calculation method of offset angle is complicated,and this method will bring more harmonic. This article proposed a kind of simple geometric algorithm and designed a user interface to calculate results more efficienttly and made optimization for harmonic cancellation to ensure that the output line voltage balance. The results of simulation validate the correctness of theoretical analysis.

关键词： multilevel of cascaded H-bridge inverter neutral offset geometric algorithm user interface Harmonic frequency

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