基于OpenCasCade的虚拟三坐标测量机碰撞检测方法

为了解决三坐标测量机测量过程中可能出现的碰撞问题,提出将虚拟空间与实际空间相结合的防碰撞方法,同时提出一种基于OpenCasCade(OCC)的快速、准确的虚拟空间碰撞检测方法.防碰撞方法在虚拟空间中建立与实际空间具有一一对应关系的虚拟模型,从而在计算机向三坐标测量机发送运动指令时先在虚拟空间中检测该指令是否会造成碰撞,将有碰撞的指令修改为无碰撞的安全指令输出,以达到防碰撞的目的.根据OCC建模的特点,可以将虚拟空间碰撞检测方法分为2步,第1步利用包围盒法快速剔除不可能碰撞的部分,第2步利用三角面片相交检测法进行较为精确的碰撞检测.为了提高速度,利用OpenMP将碰撞检测程序的计算并行化.相关的碰撞检测实验验证了该碰撞检测方法的可行性,并根据记录的数据对碰撞检测时间和精度进行了分析,证明该碰撞检测方法具有一定的实用价值.     

基于Minkowski差构造技术的凸体碰撞检测算法

碰撞检测是自然环境计算机模拟的基础，在计算机图形、CAD／CAM、机器人等领域有着广泛的应用。笔者提出了一个用于具有曲面边界凸体的碰撞检测的算法，通过构造两个凸体的Minkowski差来快速的检测两个凸体是否碰撞。当两个凸体碰撞时，算法可以快速地报告物体碰撞，并可以给出在给定方向上的穿透距离；当两个物体分离时，算法报告物体的分离，同时可以给出在给定方向上的移动距离。与已有的算法相比，这个算法可以更平衡地处理碰撞、分离的情况，该算法给出了稳定的碰撞检测条件。     

基于特征点的快速碰撞检测算法

在Lin-Canny算法的基础上,提出一种虚拟环境下面向凸体的动态、实时碰撞检测方法。该方法采用模型的特征点集合来描述其外部轮廓,通过改进的最近特征对获取方法和提出的中心定位算法来进行碰撞检测。实验给出了基于特征点的碰撞检测算法与基于包围盒算法的比较结果,证明了所提出算法的优越性。     

碰撞检测技术及在桥梁视景仿真中的应用

碰撞检测（Collision Detection）及优化是视景仿真技术中一项非常重要的技术,文中通过对碰撞检测理论的论述,概要介绍了碰撞检测算法关于时间域与空间域的不同分类方法,并讨论如何优化碰撞检测的方法,以减少运算时间与复杂度。通过视景仿真中桥梁碰撞检测的实例对碰撞检测理论及优化算法进行了验证。     

在线检测过程中碰撞检测技术的研究

在线检测过程中，规划的检测路径要求测头在实际的检测过程中避免发生碰撞。本文论述了基于三角网格模型的碰撞检测方法，提出了基于AABB包围体的碰撞检测算法，很好地解决了测头模型与零件三角网格模型的碰撞检测问题。并且提出了适于危险路径段之间零件表面形状的路径修改方法，使测头在实际检测过程中安全地绕过危险区。     

工业机器人的双透视图示教和碰撞检测

本文提出了用于工业机器人的双透视图示教算法，用于碰撞检测的图视法。这些地都应用于自行开发的机器人图形示教仿真系统中，整个系统使用Ｔｕｒｂｏ－Ｃ２．０语言在３８６ＤＸ微机上运行通过，并能与Ｒｏｂｏｔ－１机器人通讯，完成了离线示教的工作。     

一种利用Delaunay三角剖分的碰撞检测算法

虚拟现实中物体对象分布及运动情况呈现复杂多样,碰撞检测算法很难达到实时性和准确性的要求.提出了一种基于Delaunay三角剖分的多物体碰撞检测实时算法.该算法运用包围体紧密拟合物体对象,以包围体的中心构建离散数据点集,生成Delaunay三角网格,实施碰撞检测,避免层次包围盒和空间划分的不利因素,物体的更新等操作限定在局部的三角形内.实验表明在多物体的碰撞检测中,即使存在若干移动物体,算法能够满足实时性和准确性的要求.     

虚拟装备维修训练系统中碰撞可能性预检测技术

对多对象间四维时空实时碰撞检测技术进行了研究，分析了基于简单包围盒技术的碰撞检测带来的问题，设计了基于路径包围盒关键点技术的可能性碰撞检测方法．该方法利用空间平铺技术快速检测不同路径包围盒问轨迹相交的可能性．在虚拟装备维修训练系统中结合实体对象运动速度判断实体对象碰撞的可能性，用体系哈希表（Hierarchical Hash Table）查找路径包围盒间交集，构建可能碰撞路径集，采用路径检测法对可能发生碰撞的路径进行关键点分析，确定碰撞部位，提出了基于路径包围盒关键点技术的可能性碰撞检测方法的实施策略，并在虚拟维修训练系统中进行了实现．     

基于可见性查询的凸体碰撞检测算法

虚拟制造、机器人路径规划等许多应用都需进行实时的碰撞检测.论文提出一种新的凸体碰撞检测算法,此算法基于主流图形硬件的可见性查询功能,克服了同类图像空间算法需从显存回读大量数据的缺点,并可一次提交多个物体对的碰撞检测.实验表明该算法有效提高了碰撞检测的效率.     

一种集成空间分解与占用的精确碰撞检测算法及其在建筑工程中的应用

碰撞检测是建筑工程三维CAD中行之有效的辅助手段, 现代建筑形式复杂、规模庞大, 对碰撞检测算法的效率提出了更高的需求。该文基于空间分解和空间占用这两种应用最为广泛的预处理方法, 提出了一种集成、高效的精确碰撞检测算法。通过工程实例的测试和分析, 该集成算法的检测效率优于其他几种算法, 且模型量越大, 效率优势越明显。该文还针对建筑工程的实际应用需求, 对集成算法进行改进, 并应用于实际工程, 验证了算法的有效性和鲁棒性。实际应用表明, 该集成算法适用于建筑、结构、机电、幕墙等专业设计之间的碰撞检测。     

Exact collision detection for a virtual manufacturing simulator

Collision detection is a critical aspect of Virtual Reality (VR)-based simulation of manufacturing processes. Despite the significant progress that has been made in developing efficient, exact collision detection algorithms for convex objects, limited and slow progress has been reported in developing collision detection algorithms for general, nonconvex objects. To narrow this gap we introduce the concept of virtual objects which extends the applicability of exact collision detection algorithms to nonconvex objects. The outcome of our methodology is the fast creation of convex objects for a class of frequently encountered nonconvex manufacturing objects that can be used in any existing collision detection approach. The collision detection technique described in this paper is best suited for interactive simulation and animation applications where a high accuracy of object contact modeling is required. Examples include virtual assembly; mobile robot simulation; robotic painting; robotic welding; and coordinate measuring processes.     

基于VR-CAD的碰撞检测方法在EAST三环套装虚拟仿真中的应用

运动对象间的碰撞检测和碰撞响应一直是可视化虚拟环境中主要的计算瓶颈,对于大型复杂对象进行精确、实时的装配仿真等工程应用中,其时间的开销是无法忍受的。笔者提出基于CAD 的虚拟场景的装配仿真,是让CAD 软件在后台做碰撞检测,通过通讯技术,在微机上实现前台的虚拟大场景、复杂部件装配仿真的实时可视化,大大地降低了碰撞检测的时间开销。同时提高了检测的精度,并在EAST 三环吊装仿真中得到成功应用。     

虚拟生产环境中的实时碰撞检验技术

针对由机床、机器人等成百上千个物体构成的虚拟生产环境澡的实时碰撞检验问题，提出了一个由数据结构支持的层次化紧符合碰撞检验算法，解决了含凹多面体的、复杂障碍空间中多移动物体的碰撞检验问题，算法能够自动报告将要发生和已经发生的几何接触，并精确检测出两个移动物体的最小欧氏空间距离和最大干涉量，它们是计算干涉力和机器人运动规划中罚函数的重要参数，算法能够快速收敛且鲁棒性好。     

An Internet-enabled image- and model-based virtual machining system

Virtual reality (VR) can be described as a four-dimensional (4-D) simulation of the real world, including the 3-D geometry space, 1-D time and the immersive or semi-immersive interaction interface. VR applications in mechanical-related research areas are becoming popular, e.g. virtual layout design, virtual prototyping, Internet-based virtual manufacturing, etc. However, research in VR applications is facing conflicting requirements for high rendering quality and near real-time interactivity. This paper represents an Internet-based virtual machining system that builds an integrated VR scene, which combines images and models, to overcome the above conflicts. This research is divided into three parts: first, image mosaics techniques are used to implement an Internet-based virtual workshop, which is an image-based virtual scene. The method of obtaining original sequential images, the principle of image mosaics to realize automatic seamless stitching, and projection transformation matrices to reconstruct a closed inward-facing space are presented. Secondly, a model-based virtual milling machine has been constructed with three detailed approaches: a category-based dynamic graph structure to support collision detection, a relation-oriented collision detection method to improve the efficiency of collision detection, and a dynamic modelling method to model a dynamic workpiece object. Finally, an Internet-based virtual milling system, which is the integration of the image-based virtual workshop and the model-based virtual CNC machine, is constructed using the reposition method to achieve visual consistency of the virtual objects and images. This system, which includes an integrated scene, combines the advantages of image-based VR and model-based VR. Consequently, this system has both high rendering quality and good real-time interactivity.     

Impact of dynamic virtual and real robots on perceived safe waiting time and maximum reach of robot arms

This research examines perception of dynamic objects and robots in a virtual and real industrial work environment. The studies are modelled after those of Karwowski and Rahimi from the early 1990s. By applying virtual reality technology, the real workplace can be simulated in the virtual world for the improvement of facility design. Perception of hazard and risk, safe waiting time, maximum reach of robot arm are measured related to the impact of parameters such as robot size, speed and type and exposure to a virtual accident. Analysis includes techniques such as sequential experiments to compare results in the virtual and real environments. These methods may be considered as a model for studying perception and transfer in other domains. The comparison of the analysed data in the virtual and real environments helps to further determine the transferability of performance and perception from virtual reality to real. Results show similarity in perceived safe waiting time, but there are large differences in perceived maximum reach of robot arms between the virtual and real environments. Using the preliminary results from the integrated data in the sequential experiments, potential guidelines for using virtual facility layout in industry are discussed.     

A Critical Review of Laser Shock Peening of Aircraft Engine Components

Many aviation accidents are caused by the failure of aircraft engine components, and engine blades are especially vulnerable to high-cycle fatigue fracture in severe working environments as well as to impact damage caused by foreign objects. To address this problem, the United States took the lead and has been successful in implementing laser shock peening (LSP) as a surface treatment for aircraft engine components to enhance their fatigue performance. This review provides an overview of the development of LSP for use in treating aircraft engine components over the past three decades, with a brief introduction to the development of high-energy pulsed lasers for LSP. A particular focus of this review is on the limitations and challenges associated with the application of LSP for treating critical aircraft engine components. It is hoped that this review serves as a reference for future research and development that can lead to better performance of these components.     

虚拟制造中多机器人虚拟生产平台的研究

以多机器人装配作业为背景,研究了虚拟制造中多机器人虚拟生产平台系统的几何及运动学建模,多机器人协调合作策略,多机器人工作空间分配,机器人手臂的碰撞检验和避碰以及装配线意外故障的处理等关键问题,最络构建起一个完整的多机器人虚拟生产平台。     

Virtual prototyping and manufacturing planning by using tri-dexel models and haptic force feedback

This paper presents a new method of using the tri-dexel volumetric models and a haptics force feedback for virtual prototyping and manufacturing planning. In the proposed method, the initial polyhedral surface model is converted to a tri-dexel volumetric model by using a depth-peeling dexelization algorithm. In the virtual prototyping process, the tri-dexel volumetric model is updated by the swept volume of a moving cutter via a haptic force feedback interface device. A collision detection algorithm is proposed for the virtual sculpting and the pencil-cut planning with real-time haptic force feedback to the users. Tool paths are generated for machining the virtual sculpted parts via the simulation and verification on a virtual CNC machine tool before they are actually machined. Computer implementation and practical examples are also presented in this paper. The proposed method enables the haptic-aided virtual prototyping and manufacturing planning of complex surface parts.     

面向网络实验教学的虚拟协同装配技术研究

基于网络实验教学环境下对虚拟协同装配提出的不同需求,分析了其与面向设计的协同装配实现技术之间在定义、目的等方面存在的差异,提出了面向网络教学下虚拟协同装配的概念,并界定了其内涵及实现时需要考虑的因素。研究了支持协同装配的虚拟模型实验室的搭建、虚拟协同装配的语义信息表达模型和装配过程中干涉检测的方法,提出了网络协同虚拟装配实验平台体系的架构方法,并就系统的功能实现、虚拟协同装配执行过程进行了阐述,最后以柱塞泵示例了解系统的初步实现情况。     

Virtual prototyping and manufacturing planning by using tri-dexel models and haptic force feedback

This paper presents a new method of using the tri-dexel volumetric models and a haptics force feedback for virtual prototyping and manufacturing planning. In the proposed method, the initial polyhedral surface model is converted to a tri-dexel volumetric model by using a depth-peeling dexelization algorithm. In the virtual prototyping process, the tri-dexel volumetric model is updated by the swept volume of a moving cutter via a haptic force feedback interface device. A collision detection algorithm is proposed for the virtual sculpting and the pencil-cut planning with real-time haptic force feedback to the users. Tool paths are generated for machining the virtual sculpted parts via the simulation and verification on a virtual CNC machine tool before they are actually machined. Computer implementation and practical examples are also presented in this paper. The proposed method enables the haptic-aided virtual prototyping and manufacturing planning of complex surface parts.