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PLANNING AND CONTROL OF 3-D NANO-MANIPULATION

Acta Mechanica Sinica 2004年第2期20卷 117-124页

作者：李广勇席宁王越超于蒙蒙冯伟强 Department of Electrical and Computer Engineering Michigan State UniversityMI 48824USA Shengyang Institute of Automation Chinese Academy of SciencesShenyang110016China Department of Electrical Engineering Princeton UniversityPrincetonNJ 08544USA Department of Automation and Computer-Aided Engineering The Chinese University of Hong KongHong KongChina

The use of atomic force microscope(AFM)as a nanomanipulator has been evolving for various kinds of nano-manipulation *** to the bow effect of the piezo scanner of the AFM, the AFM space is different from the Cartesian *** nanomanipulation based on AFM is only a 2-D operation and does not consider the bow effect of the *** this paper,different 3-D nanomanipulation tasks using AFM such as nanolithography,pushing and cutting have been discussed. 3-D path planning is performed directly in the AFM space and the 3-D paths are generated based on the 3-D topography information of the surface represented in the AFM *** approach can avoid the mappings between the AFM space and Cartesian space in *** following the generated motion paths,the tip can either follow the topography of the surface or move across the surface by avoiding collision with *** using this method can be considered as the'true' 3-D operations since the cantilever tip can be controlled to follow any desired 3-D trajectory within the range of AFM *** experimental study shows the effectiveness of the planning and control scheme.

关键词： AFM nano-manipulation

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Numerical simulation of the effect of void fraction and inlet velocity on two-phase turbulence in bubble-liquid flows

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Acta Mechanica Sinica 2006年第5期22卷 425-432页

作者： Lixing Zhou Rongxian Li Ruxu Du Department of Engineering Mechanics Tsinghua University Beijing 100084 China Shenzhen Research Institute Tsinghua UniversityShenzhen China Department of Automation and Computer Aided Engineering The Chinese University of Hong Kong Hong Kong China

There are contradicted opinions on whether bubbles enhance or reduce the liquid turbulence. In this paper, the effect of void fraction and inlet velocity on the bubble-liquid two-phase turbulence of the multiple bubble-liquid jets in a two-dimensional channel is studied by using the two-phase second-order moment turbulence model. The results confirm the phenomena observed in experiments and reported in references that at a low void fraction and low inlet velocities the bubbles enhance the liquid turbulence, whereas at a high void fraction and high inlet velocities the bubbles reduce the liquid turbulence.

关键词： Bubble-liquid flows Two-phase turbulence Second-order moment model

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Bilateral recovering of sharp edges on feature-insensitive sampled meshes

Bilateral recovering of sharp edges on feature-insensitive s...

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作者： Wang, Charlie C. L. IEEE Department of Automation and Computer-Aided Engineering Chinese University of Hong Kong Shatin N.T Hong Kong Department of Automation and Computer-Aided Engineering Chinese University of Hong Kong

A variety of computer graphics applications sample surfaces of 3D shapes in a regular grid without making the sampling rate adaptive to the surface curvature or sharp features. Triangular meshes that interpolate or approximate these samples usually exhibit relatively big error around the insensitive sampled sharp features. This paper presents a robust general approach conducting bilateral filters to recover sharp edges on such insensitive sampled triangular meshes. Motivated by the impressive results of bilateral filtering for mesh smoothing and denoising, we adopt it to govern the sharpening of triangular meshes. After recognizing the regions that embed sharp features, we recover the sharpness geometry through bilateral filtering, followed by iteratively modifying the given mesh's connectivity to form singlewide sharp edges that can be easily detected by their dihedral angles. We show that the proposed method can robustly reconstruct sharp edges on feature-insensitive sampled meshes. © 2006 IEEE.

关键词： computer graphics

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Optimization of heterogeneous solids with level set methods

Optimization of heterogeneous solids with level set methods

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ICMA 2004 - International Conference on Manufacturing automation: Advanced Design and Manufacturing in Global Competition

作者： Wang, M.Y. Department of Automation and Computer-aided Engineering Chinese University of Hong Kong Hong Kong

ISBN: (纸本)1860584683

A heterogeneous object is referred to as a solid object made of different constituent materials. The object is of a finite collection of regions of a set of prescribed material classes of continuously varying material properties. These properties have a discontinuous change across the interface of the material regions. We present a variational framework of Mumford-Shah model for a well-posed formulation for the design of the heterogeneous solids. We discuss two approaches to the optimization problem of free-discontinuities: a multi-phase level-set model and a multi-material phase-field model, both to represent the discontinuities implicitly. These models yield a computational system of coupled geometric evolution and/or diffusion partial differential equations. Promising features of the proposed method include strong regularity in problem formulation, topological flexibility, and inherent capabilities of geometric, physical and material modeling, incorporating dimension, shape, topology, material properties, and even micro-structures within a common framework for optimization of the heterogeneous solids. The proposed methods are illustrated with several 2D examples of topology optimization of multi-material structures, material design, and compliant mechanism synthesis. © Professional engineering Publishing 2004.

关键词： Materials science

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A detection system for human abnormal behavior

A detection system for human abnormal behavior

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作者： Wu, Xinyu Ou, Yongsheng Qian, Huihuan Xu, Yangsheng Department of Automation and Computer-Aided Engineering Chinese University of Hong Kong Hong Kong

ISBN: (纸本)0780389123

This paper introduces a real-time video surveillance system which detects human abnormal behaviors. We present two approaches to such a problem. The first one employs Principal Component Analysis for feature selection and Support Vector Machine for classification of human behaviors. The proposed feature selection method is based on the border information of four consecutive blobs. The second approach computes optical flow to obtain the velocity of each pixel for determining whether a human behavior is normal or not. Both algorithms are successfully implemented in crowded environments for detecting the human abnormal behaviors, such as (1) running people in a crowded environment, (2) bending down movement while most are walking or standing, (3) a person carrying a long bar and (4) a person waving hand in the crowd. Experimental results demonstrate the two methods proposed are robust and efficient in detecting human abnormal behaviors. © 2005 IEEE.

关键词： Intelligent systems

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A system approach to solid free form design of optimal structures

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International Journal of Computational engineering Science 2004年第3期5卷 509-534页

作者： Kaza, Ramana Kumar Saikumar, Swaminathan Wang, Michael Yu Department of Mechanical Engineering University of Maryland College Park MD 20742 United States Department of Automation and Computer-Aided Engineering Chinese University of Hong Kong Shatin NT Hong Kong

Most of the work in the field of topology optimization is concentrated on using sensitivity analysis and optimality criteria methods that need explicit formulation. The design systems are often hard-coded for a specific problem with specialized optimization and FEM routines. This paper presents a work that uses a system approach to solid free form design. It attempts to develop a general topology optimization system that has a wide range of applicability by making use of sophisticated optimization and FEM packages available. A computer design system is implemented with an integration of commercial codes CFSQP and NASTRAN. A pre-processor and a post-processor are developed to assist the optimal design process. The system is tested with benchmark cases for minimum mean compliance and minimum weight designs. The results for the cases are presented, demonstrating the ability of the system to handle complex cases with practical feasibility. The implementation is evaluated with a parametric study of its performance. The key factors for the common problems of topology optimization are examined, including the mesh dependency and numerical instability. The computational efficiency is further studied to indicate the direction for further improvement of the system. © Imperial College Press.

关键词： computer aided design

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Direct estimation of the stereo geometry from monocular normal flows

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2nd International Symposium on Visual Computing, ISVC 2006

作者： Ding, Yuan Ronald, Chung Department of Automation and Computer-Aided Engineering Chinese University of Hong Kong Shatin Hong Kong

ISBN: (纸本)3540486283

The increasing use of active vision systems makes it necessary to determine the relative geometry between the cameras in the system at arbitrary time. There has been some work on on-line estimation of the relative camera geometry parameters. However, many of them are based on epipolar geometry, motion correspondences, or even presence of some calibration reference objects in the scene. In this paper, we describe a method that allows the relative geometry of two cameras be estimated without assuming that their visual fields picture the same object, nor that motion correspondences in each camera are fully estimated beforehand. The method starts from monocular normal flows in the two cameras and estimates the relative geometry parameters without evening accessing the full optical flows. Experimental results are shown to illustrate the performance of the method. © Springer-Verlag Berlin Heidelberg 2006.

关键词： Stereo vision

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Solving variational inequality problems with linear constraints based on a novel recurrent neural network

Solving variational inequality problems with linear constrai...

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4th International Symposium on Neural Networks (ISNN 2007)

作者： Xia, Youshen Wang, Jun College of Mathematics and Computer Science Fuzhou University China Department of Automation and Computer-Aided Engineering Chinese University of Hong Kong Hong Kong

ISBN: (纸本)9783540723943

Variational inequalities with linear inequality constraints are widely used in constrained optimization and engineering problems. By extending a new recurrent neural network [14], this paper presents a recurrent neural network for solving variational inequalities with general linear constraints in real time. The proposed neural network has one-layer projection structure and is amenable to parallel implementation. As a special case, the proposed neural network can include two existing recurrent neural networks for solving convex optimization problems and monotone variational inequality problems with box constraints, respectively. The proposed neural network is stable in the sense of Lyapunov and globally convergent to the solution under a monotone condition of the nonlinear mapping without the Lipschitz condition. Illustrative examples show that the proposed neural network is effective for solving this class of variational inequality problems.

关键词： Neural networks

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A Phase-Filed Method for Structural Topology Optimization with Three Material Phases

A Phase-Filed Method for Structural Topology Optimization wi...

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Collection of Technical Papers - 10th AIAA/ISSMO Multidisciplinary Analysis and Optimization Conference

作者： Wang, Michael Yu Zhou, Shiwei Department of Automation and Computer-Aided Engineering Chinese University of Hong Kong Shatin NT Hong Kong

ISBN: (纸本)1563477165

In this paper we present a phase-field method to the problem of shape and topology synthesis of structures with three materials. A single phase model is developed based on the classical phase-transition theory in the fields of mechanics and material sciences. The multi-material synthesis is formulated as a continuous optimization problem within a fixed reference domain. As a single parameter, the phase-field model represents regions made of any of the three distinct material phases and the interface between the regions. The Van der Waals-Cahn-Hilliard theory is applied to define a dynamic process of phase transition. The Γ-convergence theory is used for an approximate numerical solution to this free-discontinuity problem without any explicit tracking of the interface. Within this variational framework, we show that the phase-transition theory leads to a well-posed problem formulation with the effects of "domain regularization" and "region segmentation" incorporated naturally. The proposed phase-field method is illustrated with several 2D examples that have been extensively used in the recent literature of topology optimization, especially in the homogenization based methods. It is further suggested that such a phase-field approach may ‡ represent a promising alternative to the widely-used homogenization models for the design of heterogeneous materials and solids, with a possible extension to a general model of multiple material phases. Copyright © 2004 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

关键词： Structural analysis

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Generating spiral paths for sculptured surfaces machining

Generating spiral paths for sculptured surfaces machining

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2006 ASME International Design engineering Technical Conferences and computers and Information In engineering Conference, DETC2006

作者： Yao, Zhiyang Department of Automation and Computer-Aided Engineering Chinese University of Hong Kong Hong Kong Hong Kong

ISBN: (纸本)079183784X

To machine sculptured surfaces, ball end mills are mainly used to reach the final surface finish requirements. During machining, the cusp height is one of the major factors defining the final surface finish smoothness. A cutter path that maintains a high cutting efficiency as well as a constant cusp height is desired. Spiral curves, with the property of not requiring extra linkage segments between two adjacent arms can be used to generate a smooth cutter path. In this paper, a geometric algorithm for generating spiral cutter paths for ball end milling in machining sculptured surfaces is presented. Copyright © 2006 by ASME.

关键词： Machining

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