立体车库钢结构参数化设计分析与绘图方法

以垂直升降式立体车库钢结构骨架为研究对象,针对拓扑组成复杂而设计参数变化的立体车库钢结构,提出基于参数化方式建立三维有限元模型,采用Visual C++6.0语言编制主控程序,利用SAP50软件进行静态、动态分析,对钢结构强度、刚度和稳定性进行校核,通过分析结果的数据接口文件传递,驱动AutoCAD实现参数化绘制工程图.     

三维放射治疗计划系统的临床实验

研究由北京大学医学物理和工程北京市重点实验室和北京海思威科技有限公司合作研发的HW-Plan三维放射治疗计划系统在临床使用时的安全性和有效性。HW-PlanV1，0是三维适形放疗软件产品。本论文用HW-PlanV1．0三维放射治疗计划系统和中国医学科学院肿瘤医院的商用放疗计划系统分别对肿瘤部位和种类具有代表性的50个真实病例进行严格的放疗计划，然后对计划的结果进行分析和比较。分析方法包括1值统计方法，比较的内容包括MU值、等中心剂量值、三维剂量分布等。实验结果表明，HW．PlanV1．0能够完成临床肿瘤三维适形放射治疗计划的设计，同目前经过国内外市场准入批准的商用治疗计划系统对相同病例所做的结果在误差允许范围内一致，符合临床使用条件下的安全性和有效性要求。     

Process planning and electrode wear compensation for 3D micro-EDM

This paper presents a novel multi-cut process planning method and a new electrode wear compensation method based on a machine vision system for three-dimensional (3D) micro-electrical discharge machining (micro-EDM). Front wear and corner wear of tool electrode can be measured and compensated in a direct manner by the vision system??s image processing software capabilities. Experiments have shown that corner wear ratio (defined as a ratio between the length of corner wear and electrode diameter) is linearly proportional to machining length under a fixed machining depth condition. Track overlapping between the two adjoining paths is designed appropriately according to the corner wear ratio. Experimental results not only indicate that the proposed multi-cut process planning and electrode wear compensation methods can significantly improve machining accuracy and reduce machining time for the micro-EDM process, they also demonstrate that the X?CY dimensional errors of micro-structures can be controlled within 10???m.     

Polygon-based 3D surgical planning system for hip operation

This paper presents a light-weight software system that enables virtual three-dimensional (3D) surgical planning of hip replacement surgery for extracting 3D surgical parameters such as the position and the orientation of femoral resection plane, the interference-free trajectory of prosthesis implantation, and the final assembled position. According to the specification of an individual patient, the system allows the surgeon to design a hip prosthesis that most closely recovers the original function of the joint. Since it is based upon the 3D anatomy, the system overcomes a geometrical mismatch between prosthesis-bone interfaces which is the main limitation of 2D-based approach. The closely customized prosthesis-bone fit appears to increase the durability of hip prosthesis, and enhances the load distribution and the stability. Detailed steps of the system are described, and typical example is presented to validate the methodology. The result shows that the proposed pilot surgical planning system is applicable.     

计算机辅助三维装配顺序规划

针对三维空间装配顺序推理问题,应用方向包围盒和分离轴定理,对装配几何约束分析方法进行了扩展完善,提出三维几何约束分析方法,并开发出相应的计算机辅助分析系统.通过实例表明,该方法可以在三维装配环境中自动推理出正确完备的装配优先关系和几何可行的装配顺序.     

基于OpenGL的自动化仓库作业三维仿真

自动化立体仓库作业效率是影响物流系统运行效率的重要因素,仓库设计、存取策略等运用不当将导致系统在实际运行中出现瓶颈。因此,对自动化立体仓库作业进行建模仿真,在虚拟现实的环境中模拟仓库的运行状况非常有必要。     

基于FSS的自动化立体仓库系统建模及三维虚拟仿真

针对现代生产物流系统具有离散性、随机性的特点,以及系统仿真模型场景复杂的问题,利用系统仿真模型参数的处理及实时交互控制的实现手段,以及虚拟现实支撑软件FSS的二次开发系统实现了参数化的自动化立体仓库系统建模和人机交互控制的仿真过程。     

3D additive manufacture of oral and maxillofacial surgical models for preoperative planning

This paper investigates the errors generated during the fabrication stage for producing complex anatomical replicas derived from computed tomography coupled with the 3D additive manufacturing methods. Based on this research work, it is shown that patient-specific model based on computed tomography data can be converted into computer numerically controlled G-code. It is shown that 3D extrusion-based additive manufacturing technology is accurate to ±3 % equating to ±200 μm surface deviations due to plastic shrinkage and distortion formed during the process. Polylactic acid plastic extrusion through a 200-μm bore nozzle has resulted in a model being produced with an R_a roughness of 35.5 μm. An evaluation on the errors generated during the fabrication process has been used to accurately produce an adult female mandible. Internal nerve channels and complex external bone geometry has been produced within the model. It is shown that using this process results in bone complexity and accuracy required for producing low-cost surgical grades models which is in comparison with traditional selective laser sintering manufacturing techniques. The surface accuracies suggest that the reproduction of anatomically complex representative structures by 3D plastic extrusion additive manufacturing which can be used for pre-surgical planning.     

物体三维数字化中的机器视觉视点规划方法

介绍了机器视觉系统的组成,对视点规划方法进行分类,分别阐述了基于模型和未知模型的视点规划方法研究情况,分析目前视点规划研究中需要解决的遮挡问题,最后展望了视点规划的研究方向．     

3D环境下飞机装配工艺规划与仿真一体化模型

为实现3D环境下飞机装配工艺规划与仿真过程的集成和统一,提出了一种飞机装配工艺一体化模型。该模型综合了装配工艺设计对产品对象以及工装、工具等资源对象在信息组织管理、零件几何运动描述等方面的要求,确定了装配＂产品—资源—工艺＂间的层进映射关系,将产品对象和资源对象间复杂的1∶N或N∶1关系分解为具体的1∶1关系,并基于文件对象结构原理建立了其数学表示模型。以某飞机中央翼部件装配为例,将该建模方法应用到自主开发的数字化飞机装配工艺规划与仿真系统中,验证了所提方法的有效性。     

基于UG的行星齿轮传动三维建模及运动仿真

1 UG软件简介 UG是美国UGS公司发布的CAD／CAE／CAM一体化的三维参数化设计软件,它在汽车、航空航天、通用机械等领域有广泛的应用。UG提供了一个基于过程的产品设计环境,使产品开发设计到加工和分析实现了数据的无缝集成。     

MBD环境下的三维机加工艺设计技术

针对基于模型定义技术对工艺设计带来的变革,在定义工艺模型、工序模型和工序参考模型的基础上,建立了基于模型定义环境下的三维机加工艺设计模式。以工艺方法为核心,集成工艺参数信息、资源信息和检验信息,构建了一种三维工艺信息标注符号。从标注面、相关性查询、成组标注、限定区域和颜色的使用等方面制定了三维机加工艺信息标注规范。开发了三维机加工艺设计系统,并以某零件为例,验证了方法的有效性。     

Sensitivity analysis of a validated subject-specific finite element model of the human craniofacial skeleton

Developing a more complete understanding of the mechanical response of the craniofacial skeleton (CFS) to physiological loads is fundamental to improving treatment for traumatic injuries, reconstruction due to neoplasia, and deformities. Characterization of the biomechanics of the CFS is challenging due to its highly complex structure and heterogeneity, motivating the utilization of experimentally validated computational models. As such, the objective of this study was to develop, experimentally validate, and parametrically analyse a patient-specific finite element (FE) model of the CFS to elucidate a better understanding of the factors that are of intrinsic importance to the skeletal structural behaviour of the human CFS. An FE model of a cadaveric craniofacial skeleton was created from subject-specific computed tomography data. The model was validated based on bone strain measurements taken under simulated physiological-like loading through the masseter and temporalis muscles (which are responsible for the majority of craniofacial physiologic loading due to mastication). The baseline subject-specific model using locally defined cortical bone thicknesses produced the strongest correlation to the experimental data (r2 = 0.73). Large effects on strain patterns arising from small parametric changes in cortical thickness suggest that the very thin bony structures present in the CFS are crucial to characterizing the local load distribution in the CFS accurately.     

基于三维加工特征的工艺优化设计系统

三维CAD/CAPP的应用要求表明,三维工艺设计不仅要解决不同设计与工艺模型之间的数据获取与传输,而且还要考虑工艺优化的环境与全局性.利用基本几何面单元来表达三维加工特征并结合特征的制造信息和资源约束,建立了基于设计模型与工艺模型的统一数据模型;然后在工艺准则、资源加工能力和用户自定义的约束条件下进行工艺优化;最后根据生产环境进行综合评价并选择最优的工艺方案.     

仿壁虎机器人地壁过渡步态规划与运动仿真

针对传统仿壁虎机器人空间运动能力不足、空间运动步态方法的可行性问题,基于仿生学原理,设计了一种具有腰关节的每条腿具有三个自由度的四足仿壁虎机器人,对仿壁虎机器人的结构进行了正运动学和逆运动学的分析,建立了各关节角度和机身空间坐标系下各参量之间的关系,在地面与墙壁交角为90°的工况下,根据其关于纵向平面对称的结构特点提出了一种对称式地壁过渡步态方法。在Matlab软件上对该步态方法的可控性进行了评价,利用各关节角度与各参量之间的函数关系编程得到了地壁过渡过程中各关节角度、角速度曲线,并在Inventor环境下进行了运动学仿真实验。研究结果表明,各关节角度、角速度均在允许范围内,且角度函数一次连续,验证了结构的合理性和步态的可行性。     

无人机3D航迹规划及动态避障算法研究

规划一条高时效且低代价的三维(3D)航行轨迹,成为目前无人机广泛应用亟须解决的问题。针对蚁群算法在航迹规划中出现的航迹长度和平滑性不足问题,通过改进蚁群系统中的节点移动规则、构造多重启发信息并结合粒子群优化算法的全局搜索能力,提出了蚁群粒子群融合算法。同时,就飞行航迹中出现的动态避障问题和目标点变化问题,提出了改进生物启发神经动力学模型算法,该算法针对3D静态最优航迹中出现的障碍物和目标点变化,实现了局部在线航迹调整。实验仿真结果表明,蚁群粒子群融合算法能在3D静态环境中规划出一条期望航迹。同时,改进生物启发神经动力学模型算法不仅能对突发障碍动态避障,还能对动态目标点变化实时跟踪。     

基于UG的纸箱自动钉合设备三维模拟设计

纸箱的最后一道工序接合,是决定产品质量好坏的一个重要因素。目前,国内接合方式最普遍的是钉接法,其最主要设备是钉箱机。对现有的钉箱机进行了研究之后,为了实现一种钉合质量更高的全自动钉合设备,采用纸箱板不动钉头运动。工作台的两侧分别放置一个翻折机构,纸箱板沿一个侧边压痕翻折180°。纸箱板内侧的中间部位设置一块盖板用于配合其上部钉头实现钉合,电动机带动钉头对纸箱板的钉合。整个机构结构简捷、机构钉合尺寸精度高,钉合速度快。现阐述基于UG三维平台下,纸箱自动钉合设备的设计方法和设计点,并对设计结果进行了动态模拟仿真和优化。