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Force Feedback Coupling with Dynamics for Physical Simulation of Product Assembly and Operation Performance

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Chinese Journal of Mechanical Engineering 2015年第1期28卷 164-172页

作者： LIU Zhenyu TAN Jianrong DUAN Guifang FU Yun state key laboratory of cad&cg Zhejiang University

Most existing force feedback methods are still difficult to meet the requirements of real-time force calculation in virtual assembly and operation with complex objects. In addition, there is often an assumption that the controlled objects are completely flee and the target object is only completely fixed or flee, thus, the dynamics of the kinematic chain where the controlled objects are located are neglected during the physical simulation of the product manipulation with force feedback interaction. This paper proposes a physical simulation method of product assembly and operation manipulation based on statistically learned contact force prediction model and the coupling of force feedback and dynamics. In the proposed method, based on hidden Markov model （HMM） and local weighting learning （LWL）, contact force prediction model is constructed, which can estimate the contact force in real time during interaction. Based on computational load balance model, the computing resources are dynamically assigned and the dynamics integral step is optimized. In addition, smoothing process is performed to the force feedback on the synchronization points. Consequently, we can solve the coupling and synchronization problems of high-frequency feedback force servo. low-frequency dynamics solver servo and scene rendering servo, and realize highly stable and accurate force feedback in the physical simulation of product assembly and operation manipulation. This research proposes a physical simulation method of product assembly and operation manipulation.

关键词： contact force prediction force feedback multi-rate coupling physical simulation of manipulation virtual assembly

Decomposition Method of Complex Optimization Model Based on Global Sensitivity Analysis

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Chinese Journal of Mechanical Engineering 2014年第4期27卷 722-729页

作者： QIU Qingying LI Bing FENG Peien GAO Yu state key laboratory of cad&cg Zhejiang University

The current research of the decomposition methods of complex optimization model is mostly based on the principle of disciplines, problems or components. However, numerous coupling variables will appear among the sub-models decomposed, thereby make the efficiency of decomposed optimization low and the effect poor. Though some collaborative optimization methods are proposed to process the coupling variables, there lacks the original strategy planning to reduce the coupling degree among the decomposed sub-models when we start decomposing a complex optimization model. Therefore, this paper proposes a decomposition method based on the global sensitivity information. In this method, the complex optimization model is decomposed based on the principle of minimizing the sensitivity sum between the design functions and design variables among different sub-models. The design functions and design variables, which are sensitive to each other, will be assigned to the same sub-models as much as possible to reduce the impacts to other sub-models caused by the changing of coupling variables in one sub-model. Two different collaborative optimization models of a gear reducer are built up separately in the multidisciplinary design optimization software iSIGHT, the optimized results turned out that the decomposition method proposed in this paper has less analysis times and increases the computational efficiency by 29.6%. This new decomposition method is also successfully applied in the complex optimization problem of hydraulic excavator working devices, which shows the proposed research can reduce the mutual coupling degree between sub-models. This research proposes a decomposition method based on the global sensitivity information, which makes the linkages least among sub-models after decomposition, and provides reference for decomposing complex optimization models and has practical engineering significance.

关键词： multidisciplinary design optimization collaborative optimization sensitivity analysis coupled factorization iSIGHT

Real-time camera tracking using hybrid features in mobile augmented reality

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Science China(Information Sciences) 2015年第11期58卷 211-223页

作者： WANG WeiJie WAN HuaGen state key laboratory of cad&cg Zhejiang University

Often only simple features are employed in mobile augmented reality(AR) due to the limited computational capacity of mobile terminals, which often leads to unsteadiness of the camera tracking. In this paper, we propose a novel approach to real-time camera tracking in mobile AR using hybrid features to alleviate this problem. By integrating feature points and lines as scene features, hybrid features are generated through the process of point/line features extraction, optimization and fusion, and are used in the real-time estimation of camera parameters. A method for image feature optimization is proposed based on the scene structural analysis to meet the computational constraints of mobile terminals. In order to improve the stability of camera tracking, an iterative screening method is proposed to choose a set of stable feature lines, and hybrid features are adaptively constructed based on the composition and geometry of scene features. It is shown from the experimental results that the proposed method produces more stable and smoother camera trajectories in comparison with the method only using feature points, and a good balance is achieved between the stability and the real-time computation of the camera tracking on a mobile platform.

关键词： mobile augmented reality feature extraction camera tracking hybrid feature mobile platform

Smooth feature line detection for meshes

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2005年第5期6卷 460-468页

作者：郭延文彭群生胡国飞王进 state key laboratory of cad & cg Department of Mathematics Zhejiang University Hangzhou 310027 China state key laboratory of cad & cg

In this paper the authors present a novel semi-automatic feature line detection technique for meshes. Taking into account the distance and orientation between two vertices on meshes and the curvature information of vertices, they first find an initial feature line which connects some user-specified vertices on meshes; then parameterize the “feature strip” surrounding the feature line onto a planar domain using a vertex flattening technique; and refine the flattened feature strip using the 2D snakes approach to make the feature line smoother and more accurate; lastly they get the feature line by mapping the refined line back to the original meshes. Experimental results showed that their method can extract the feature line rapidly and precisely. As an ap- plication, they propose a mesh decomposition method based on the detected feature line.

关键词： Feature line Image snakes Mesh parameterization Mesh decomposition

Interactive sculpting of product shape based on constraint manipulation in virtual environment

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2005年第7期6卷 733-740页

作者：刘振宇谭建荣 state key laboratory of cad & cg Zhejiang University

In product concept design, not only designers with professional cad skills, but also final customers take part in the design and evaluation of product shape styling. Because customers usually lack surface modelling background and are not familiar with concrete operations of commercial cad systems, it is difficult for them to express their change intentions of product shape through professional cad tools if they are not satisfied with the current shape design. This paper puts forward a method for creating, dragging and manipulating constraint and load represented in form of icon entity in interactive sculpting of product shape in virtual environment. The method supports customers manipulation of sculpting constraints or loads on sculpting shapes in virtual reality interaction to control the deformation of product shape. Constraints management based on icon entity is similar to spline lofting operation that is familiar to engineers, so users do not need to know surface details or have any professional knowledge of surface modelling, by only using their physical and engineering experience, they can manipulate the sculpting of product shape intuitively.

关键词： Virtual design Constraint manipulation Shape sculpting Concept design

Efficient polygonization of tree trunks modeled by convolution surfaces

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Science China(Information Sciences) 2013年第3期56卷 48-59页

作者： ZHU XiaoQiang GUO XueKun JIN XiaoGang state key laboratory of cad & cg Zhejiang University

We present an efficient polygonization approach for tree trunks modeled by line skeleton-based convolution surfaces.A quad-dominated non-convex bounding polyhedron is firstly created along the skeleton,which is then tetrahedralized and subdivided into the pre-defined *** that,the iso-surface within each tetrahedron is extracted using marching *** algorithm can generate polygons with adaptive edge lengths according to the thickness of the *** addition,we present an efficient CUDA-based parallel algorithm utilizing the high parallelism of the tetrahedron subdivision,the potential field calculation,and the iso-surface extraction.

关键词： trunk modeling skeleton-based modeling convolution surface tetrahedral subdivision CUDA

Construction of the Inference Engine of Blast Furnace Expert System

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Journal of Iron and Steel Research International 1998年第2期5卷 24-29页

作者： Liu Jinkun Wang Shuqing state key laboratory of cad & cg Zhejiang University

The expert system for judging blast furnace condition is built to realize automatic judgment of blast furnace conditions and standardization of blast furnace operation. This paper discusses the design and implementati... 详细信息

关键词： blast furnace expert system inference engine

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Dual quaternion based virtual hand interaction modeling

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Science China(Information Sciences) 2013年第3期56卷 27-37页

作者： CHEN WenFeng ZHU ShuJing WAN HuaGen FENG JieQing state key laboratory of cad & cg Zhejiang University

Virtual hands play key roles in three-dimensional interaction in various virtual reality ***,their visual realism has seldom been seriously discussed in the community of human computer interaction,not to mention the challenging balance between their visual/motion realism and real-time *** this paper,a novel approach for virtual hand interaction modeling based on dual quaternion is ***,dual quaternion blending(DQB) is introduced as pseudo muscular layer of our virtual hand model instead of traditional linear blending(LB) and quaternion blending(QB) due to its advantages in muscular deformation.A framework for virtual hand interaction is proposed which supports both gesture interactions and 3D *** results show that our proposed virtual hand interaction model is suitable for most virtual reality applications and achieves good visual/motion realism while maintains real-time performance.

关键词： virtual reality virtual hand interaction dual quaternion gesture interaction 3D manipulation

Motion Planning for Industrial Robots Based on Task Process Decomposition

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Chinese Journal of Mechanical Engineering 2010年第2期23卷 135-141页

作者： BU Wanghui LIU Zhenyu TAN Jianrong state key laboratory of cad ＆ cg Zhejiang University Hangzhou 310027 China

The existing research of the industrial robotic motion planning mainly focuses on the trajectory planning and the path planning, which aim at obtaining a minimum-time trajectory and finding an obstacle-free path respectively. In the trajectory planning, the jerks of robotic joints are usually not considered, so the smoothness of the robotic motion cannot be ensured. In the path planning, the complex spatial curves generally cannot be tracked easily, and it needs the fussy teach-and-playback operation. In this paper, based on the different constraint characteristic of the variable motion phases in the practical robotic task, the complicated task is decomposed into two kinds of sub processes, which are the free motion process and the constrained motion process. In the free motion process, the kinematic models of quasi trapezoidal waveform and quasi triangular waveform are proposed with the dynamic limits of maximum velocities, accelerations and jerks of robotic joints, so the minimum-time trajectory can be obtained with the motion smoothness. In the constrained motion process, the mathematical presentation of the task paths is extracted from the cad models of the workpieces, so the complex spatial curves can be tracked autonomously without much teaching operation. In addition to the theoretical research, a robotic virtual prototyping system is also developed for the industrial arc welding production. The proposed research ensures the robotic motion smoothness, enhances the ability for tracking the complex spatial curves, and improves the quality and efficiency of the robotic motion planning.

关键词： robotic manipulator trajectory planning path planning virtual prototyping