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30 April 2013, Volume 34 Issue 2 Previous Issue    Next Issue

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A Subdivision Algorithm for Voronoi Diagram of Planar Point Set Shou Huahao, Yuan Ziwei, Miao Yongwei, Wang Liping 2013, 34(2): 1-5.  Abstract ( 111 )   PDF (386KB) ( 181 )   Voronoi diagram is one of the most important concepts in computational geometry, It is applied widely in computer graphics, computational geometry, computer aided geometric design, finite element grid partition, robot trajectory control, pattern recognition, meteorology and geology. Based on quadtree data structure and interval arithmetic technique, a new subdivision algorithm for Voronoi diagram of a planar point set is proposed. A comparison of this subdivision algorithm with the well known incremental algorithm and grid expansion method is conducted. Test results show that the subdivision algorithm is more efficient. The most important is that the idea of subdivision algorithm is very simple and therefore it is easy to implement. Related Articles | Metrics

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Constraint Based Error Metric for Dynamic Terrain Visualization Yu Ping, Zhang Caiming 2013, 34(2): 7-12.  Abstract ( 62 )   PDF (625KB) ( 189 )   The error metric determines the number of triangles per frame, and affects the fidelity of terrain and efficiency of the algorithm in real-time rendering in dynamic terrain visualization. The screen error calculation method requires a lot of maintenance work and produces a large number of redundant triangles to eliminate T-junction and crack in the real-time rendering. So this will reduce the speed of real-time rendering of terrain. In this paper, the local roughness factor constraint nested sphere of error metric is used to provide a better reflection of the details of local topography and reduce redundancy triangles in flat region. Computation complexity in real-time rendering can be reduced by using the delay estimate frame coherence and thus the efficiency of the algorithm can be further improved. Experiments demonstrate that the dynamic terrain visualization algorithm, by using the error metric with constraints, can effectively reduce the redundant triangles and can represent the deformed region very well in real-time rendering with improved efficiency. Related Articles | Metrics

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Improvements of Dynamic Programming Stereo Matching Algorithm Based on Parallax Region Segmentation Wang Jingdong, Chen Si, Li Xiuxin, Xu Lihong 2013, 34(2): 13-20.  Abstract ( 104 )   PDF (785KB) ( 260 )   Stereo matching algorithm based on dynamic programming (DP) can meet real-time constraints even on low-cost hardware. Therefore, it can be used in Robot obstacle avoidancing system. But the performance of conventional DP has not been satisfactory and scattered mismatching points occur when the stereo matching is applied. To solve these problems, the method of initial cost getting and path traversal and backtracking is improved. The energy aggregation method is proposed which can use the information of object boundary to determine the disparity changing regions. A highly accurate initial disparity map is obtained, which can make the subsequent phases of parallax getting get a good performance. In the path traversal and backtracking phase, the idea of multi-path backtracking to exploit the information gained from DP more effectively is also introduced. More reliable pixels to reduce the occurrence of mismatch can be retained. The experiment shows that this method has a high matching accuracy and a fast speed. Related Articles | Metrics

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Multi-focus Circle, Ellipse and Ovals Guan Xiangen, Guan Jie 2013, 34(2): 13-64.  Abstract ( 66 )   PDF (610KB) ( 249 )   Ovals are familiar but not yet well-known basic graphics. To explore the understanding for them the concept of multi-focus circle is put forward to explore the inherent properties of the standard ellipse and ovals. Ellipses have two standard types, linear two focuses and rhombus four focuses, and the oval is the specific fusiform four focus circle. Based on the analysis, a special kind of parameter simulation method and some examples are given, which deepens the basic understanding for ovals. Related Articles | Metrics

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Algorithm Design and Comparison of Kalman and FIR Filter Methods for Image Stabilization of Robot Vision Jin Yinglian, Wang Binrui, Xu Yin 2013, 34(2): 21-25.  Abstract ( 94 )   PDF (537KB) ( 224 )   Image stabilization is the key for accurate docking operations of robots with vision. The whole algorithm of image stabilization is established, including images kinematics model, KLT feature pixels detecting, SAD feature pixels matching and filters. Kalman and FIR filters are designed for smoothing images motion parameters and built in MATLAB. Simulation of filter of motion un-intended parameters is implemented to indicate removing jitter effect. Kalman filter is compared with FIR filter. Comparison curves and tables are given , which demonstrate that Kalman filter is better than FIR in robot vision image stabilization process. Based on VC++ and OpenCV, image stabilization software is programmed, and experiments are completed on double moving robots docking operation platform. The algorithm running time is less than the sampling period, and the precision and real-time demands are contented. Related Articles | Metrics

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Optimal Packing of Irregular Parts on Plates with Defects Dong Dewei, Yan Yunhui 2013, 34(2): 31-37.  Abstract ( 75 )   PDF (467KB) ( 179 )   Aiming at the optimal packing problem of irregular parts, known as a NP-complete problem, an approach is presented, which combines adaptive niche genetic simulated annealing algorithm with a heuristic packing algorithm based on the lowest point of inside no fit polygon. Considering that the choice of crossover probability and mutation probability will affect algorithm convergence, the adaptive crossover probability and the adaptive mutation probability are putted forward. The proposed approach automatically looks for the best sequence of the irregular parts and each part’s optimum rotation angle by the genetic simulated annealing algorithm which is based on the niche technology. The lowest point of inside no fit polygon, which is created by the damaged raw material polygon and the irregular part polygon, is selected to locate the part. Meanwhile, the overlap of the part and the surface defect of raw material are avoided. Examples indicate that the approach is effective and practical. Related Articles | Metrics

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Automatical Generation of Technology Process and its Relations for Automotive Wiring Harnesses Zhu Jiman, Xu Benzhu, Ling Xinnan, Liu Xiaoping 2013, 34(2): 38-46.  Abstract ( 60 )   PDF (394KB) ( 313 )   Quickly and accurately identifying each process and their constraint relations between each other from the complex wiring harness drawings is the basis for formulating process routes. According to the knowledge of automotive wiring harness and the process characteristics of wiring harness components, the model of harness process graph is established. Then the algorithm for identifying processes automatically is researched, finally the relationship between procedures by introducing the constraint matrix is described to lay a good foundation for harness process planning and production scheduling. Related Articles | Metrics

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Clearing Approach for Foggy Image Using Local Nonlinear Diffusion Mean Shift Retinex Zhang Hongkun, Xue Mogen, Zhou Pucheng 2013, 34(2): 47-51.  Abstract ( 73 )   PDF (536KB) ( 244 )   To solve the problem of halo artifacts in the presence of high contrast edges and color distortion when using traditional Retinex algorithm to deal with foggy images, a kind of nonlinear diffusion mean shift filtering-based Retinex enhancement algorithm is proposed. Firstly, the dynamic domain of the foggy image is adjusted by means of wavelet analysis. And then, the incident light information is estimated by use of nonlinear diffusion mean shift filter-based smoothing, thus the approximate scenery reflectance can be obtained. Finally, by adjusting the saturation difference between before and after processing, compensation for saturation loss because of image smoothing is done within lαβ color space. Experimental results have shown that the proposed algorithm can not only improve the degree of clearness of foggy images, but also overcome the color distortion and halo phenomena. Related Articles | Metrics

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Developable Tangent Surface of Rotary Surface Mao Xin, Yang Jinglin, Ma Mingxu 2013, 34(2): 65-71.  Abstract ( 98 )   PDF (403KB) ( 184 )   The general theory and method to construct the developable tangent curved surface of rotary surface and mapping analysis between them are put forward systematically, the mathematical model and mapping relationship of the developable tangent cylinder and developable tangent cone of rotary surface are established. The differential equations of the extreme value mapping curve and equidistant mapping curve are put forward according to the theory of differential length ratio between the rotary surface and its developable tangent curved surface. The deformation of mapping will be grasped accurately by the whole and local deformation analysis. Related Articles | Metrics

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Hausdorff Distance between Cubic Bézier Curve and Circular Arc with a Coincidence Point Zhang Songzhi, Wang Xuhui, Tang Shuo 2013, 34(2): 72-75.  Abstract ( 105 )   PDF (247KB) ( 179 )   Hausdorff distance is often used to measure the distance between two curves. It can be used to measure the distance between cubic Bézier curve and circular arc. In the paper, the closed form of the Hausdorff distance between the circular arc and the cubic Bézier curve is given when they have a coincidence point. Related Articles | Metrics

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3D Bridge Modeling based on Parametric Design Wu Xueyi, Liu Junshou, Yin Heng 2013, 34(2): 76-82.  Abstract ( 115 )   PDF (367KB) ( 249 )   Parameter design is an important means of the geometric modeling, three-dimensional visualization of the bridge is the development trend of today's bridge information technology. In order to satisfy the needs of visualization of the bridge appearance using parametric design method, the principles and methods of the geometry of parametric modeling are deeply discussed. Combining the characteristics of the bridge structure, geometric information and topological information of nine major bridge component structures (such as T beam, beam-column type pier, light abutment, etc.) are analyzed, the parametric design of bridge components is presented in details, the three-dimensional modeling of bridge components is realized; special primitives and components (such as arc inverted angle pier, abutment slope protection) rendering algorithm is studied. According to topological relations based on the spatial location of each component, bridge can be rapid spliced which uses parametric variables to drive calculation of the spatial position coordinates of each component. After completion of the bridge 3D parametric modeling drived by parameters, the user can visualize the design results. The 3D parametric bridge visualization system achieves fined model, thorough parametric, fast , clear classification, and good visual effects. Related Articles | Metrics

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Drawing Automatic Generation and Optimization based on Immune Genetic Algorithm Zhu Xuemin, Wang Zongyan, Yang Fen, Wu Shufang, Lu Chunyue 2013, 34(2): 83-88.  Abstract ( 71 )   PDF (361KB) ( 164 )   In current three-dimensional model parametric variations, there exist the problems of unreasonable view layout ,imbalance, and marked confusion after drawings change, and also the technical limitations of adjustment. In this paper, the immune genetic algorithm is used in drawings optimization and adjustment. Based on the template parameter driven, it realizes drawings automatic generation and optimization in view of layout and proportion, and its various label location. It has been proved that the method can realize intelligent rapid drawing, ensure the accuracy of the design, and improve design efficiency and quality. Related Articles | Metrics

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Optimization Design of UAV Ground Control Panel Layout Huang Yulong, Yu Suihuai, Yang Yanpu, Li Zheng 2013, 34(2): 89-93.  Abstract ( 119 )   PDF (423KB) ( 196 )   The layout of Unmanned Aerial Vehicle(UAV) ground control panel relates to the UAV launch and air safety directly. On the base of the ergonomics analysis and integrating the design principal of control panel layout and human factors, the improved method of the control panel layout is proposed. Setting the optimization design of a UAV control panel layout as an example, software Jack is used to analyze the field of vision and accessible domains, the rationality of the improved design is then proven. Related Articles | Metrics

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Application of Model View Management in Building Collaborative Design Zhou Cheng, Deng Xueyuan 2013, 34(2): 94-97.  Abstract ( 94 )   PDF (293KB) ( 181 )   Architectural design involves multi-disciplinary collaboration and the sharing and exchange of large building data set, a great part of which is model view information. As one of the key technologies of building collaborative design, model view management is foundational to coordinate the information sharing and exchange among disciplines. The technological characteristic of layer-based and object-based view management is researched, and the implementing measures of model view management both in 2D collaborative design and 3D model-based collaborative design are presented. Based on the above measures, the implementation of model view management of collaborative design in the platforms of AutoCAD and Revit is presented. Related Articles | Metrics

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Application of CAD Professional Standards in Building Collaborative Design Lin Liangfan, Deng Xueyuan 2013, 34(2): 101-107.  Abstract ( 68 )   PDF (304KB) ( 200 )   Building collaborative design is the key factor of information construction for survey and engineering design enterprises, and the establishment of CAD standard is the premise and basis of building collaborative design. Thus, the paper carries out a systemic research on CAD standards, firstly describes the development and the present situation of domestic CAD standards, then points out some existing problems and gives out the solutions in detail with a practical case of the implementation of CAD standards in Shanghai ECUC Group. Finally, the application of CAD standards in building collaborative design is summarized together with further development of BIM-based building collaborative design platform. Related Articles | Metrics

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A UG-Based Parametric Design System Shi Liyuan, Zhu Xijing, Ma Jizhao 2013, 34(2): 108-112.  Abstract ( 140 )   PDF (543KB) ( 446 )   This paper puts forward a parametric design method based on sketch assembly and sketch constraint by taking the parametric modeling of power ultrasonic honing device as an instance. This method uses the sketch function of UG modeling to conduct geometric constraint and size constraint on parts’ models so as to , establish the relations between the variable sizes of multiple parts and assembly sketches in function expressions. It can realize the linkage between assembly parts by managing the variable sizes in the assembly sketches. Related Articles | Metrics

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Process-modeling and Application in Virtual Maintenance based on Petri Net and Semantic Network Liu Jiaxue, Liu Tao, Geng Hong 2013, 34(2): 113-118.  Abstract ( 73 )   PDF (410KB) ( 279 )   To address the problems of enormous maintenance process modeling, non-repeatability of maintenance procedure and complex relation in the current virtual maintenance process, Training Join net (TJ net), a process modeling method——combining Petri Net with Semantic Network, is presented. The upper of TJ net decomposes component structure logically and clusters resources formally according to the size of the components based on Semantic Network, and thus realizes logical connection of components. The lower part abstracts some improved element model based on Petri Net and the transition and fire rules of Petri Net, and thus improves the model universality and the efficiency of modeling. And it achieves property state information sharing by the state-collection module., The TJ net has been validated by the instance of virtual maintenance of aircraft electronic equipment in the virtual maintenance platform. Related Articles | Metrics

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Simulation of Virtual Maintenance Process based on Parameterized Action Representation Wang Fengchan, Sun Youchao 2013, 34(2): 119-124.  Abstract ( 87 )   PDF (377KB) ( 201 )   Parameterized Action Representation (PAR) designed to bridge the gap between natural language instructions and the virtual agents who are to carry their action for virtual maintenance process. PAR is therefore constructed based jointly on implemented motion capabilities of virtual human or agent action for instruction interpretation. Maintenance Task Decomposition Model and Actions Database (Action-DB) is presented based on the PAR and Intelligent Virtual Maintenance Training System in Delmia environment in this paper. And a real time execution architecture controlling 3D animated virtual human or agent is proposed based on PAR model. Finally, an example is given to verify the simulation process of models and method proposed. And results show that PAR Action-DB is convenient to simulate the virtual maintenance process. Related Articles | Metrics

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Comparison of Education and Course of Engineering Graphics and CAD between China and United States Universities Zhang Yan’e, Chulho Yang, Li Li 2013, 34(2): 125-129.  Abstract ( 96 )   PDF (216KB) ( 291 )   The Engineering Graphics and CAD is a compulsory course for undergraduate engineering student. The course introduces the technical drawing, the method and technology of the engineering drawing of the parts and assembly parts, and computer tools of CAD to the students. According to the data and information obtained from the actual course in China and US， a systematic comparison on course objectives, contents, teaching method, facilities and environments offered by a Chinese university and a US university is made. A questionnaire including the interests of the students, the usefulness of the knowledge, etc. has been designed to collect information in both universities in fall semester 2011. The collected information has then been summarized and analyzed. Overall, a reforming suggestion is put forward for the course of the Engineering Graphics and CAD. Related Articles | Metrics

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Solid Modeling Method Based on Feature Profiles Zhang Xiuzhi, Yan Guan, Zhang Yunhui, Hou Hongsheng 2013, 34(2): 130-135.  Abstract ( 71 )   PDF (310KB) ( 229 )   The modeling process of most solid structures in engineering graphics course can be seen as the results of feature profiles’ movements, usually stretching, cutting or rotating. Combining teaching practice of engineering graphics and 3D CAD course, a solid modeling method based on feature profiles is summarized. The feature profile that shows the shape of a solid is extracted from 2D views, then through stretching, cutting, rotating or the unite of them, a 3D solid is modeled. Some ramificate solid modeling methods are proposed, such as single feature profile, single direction multi-feature profile, bidirectional feature profiles, bidirectional multi-feature profiles, etc. Solid modeling process can be greatly simplified with feature profile method, especially bidirectional feature profiles method. Related Articles | Metrics

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International Teaching Practice of Engineering Drawing Based on Parametric Modeling Design and Representation Luo Huifu, Jiao Yonghe 2013, 34(2): 136-140.  Abstract ( 81 )   PDF (327KB) ( 238 )   In the engineering drawing teaching practice of international program for mechanical engineering major, the concept of parametric, variational and constraint design, which are typical in modeling design, is introduced, and the fundamentals of geometric drawing and view projection are simplified while the ability of design and representation with 3d modeling software is emphasized. With modeling design in assembly environment, assembly design and parts modifying become easier than before. All lectures are given in English with ISO standard during the whole course. Chinese standard (GB) is introduced for contrast when it is different with ISO. With the training of this course, learners will possess the fundamental ability of international communication in mechanical engineering and obtain the skills of design and representation which are the object of later course training in traditional program. Related Articles | Metrics

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Course Design and Development of Work-based Learning for Reading and Drawing Machine Drawings Wang Xinrong 2013, 34(2): 141-147.  Abstract ( 64 )   PDF (223KB) ( 213 )   Currently, the work-based teaching approach is quite effective for higher vocational education. Taking the mechanical drawings and CAD and drawing courses for mechanics specialties as examples, this paper is to provide a discussion on the design and development of a work-based learning course for reading and drawing machine drawings through a work-based process-oriented restructuring of the knowledge architecture under the discipline system, with an aim to better connect schooling and work content with zero “adjusting period”. Related Articles | Metrics

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Fast Document Properties Generation and National Standardization of Title Block in Inventor Liu Yang, Gu Xiaotong, Tang Chuanling, Ding Birong, Wang Jing 2013, 34(2): 148-152.  Abstract ( 129 )   PDF (272KB) ( 210 )   For the generation of Inventor part document, assembly document properties and drawing document title block information, an object-oriented API method is provided,which uses VB. NET language as a development tool and applies the add-in way to integrate document properties such as the designer, checked by title, part number and so on into a simple user-defined interface. It improves the properties generation rate and at the same time deals with the title block GB1 provided by Inventor itself and makes unassociated data, such as the scale and process, connect again. It realizes the reconstruction of the information and the national standardization of title block, expands the function of the Inventor end-user interface. Related Articles | Metrics

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Research and Implementation of Parametric Parts and Components Library Yang Xiangang, He Yulin, Du Jing, Jin Xin, Li Chengwu 2013, 34(2): 153-158.  Abstract ( 76 )   PDF (378KB) ( 346 )   On the basis of describing the relationship between features, tabular layout of article characteristics, design with features and parametric design, the paper proposes an insight into how to parameterize parts/components on general CAD systems. Based on the research of customized development on Inventor, the methodology of building parametric parts/components library and developing key implementation code on Inventor is put forward. Instance of case study is performed and demonstrates the feasibility of the methodology. Related Articles | Metrics