1814_酸奶桶的反求造型研究(只WORD文档)
1814_酸奶桶的反求造型研究(只WORD文档),酸奶,造型,研究,钻研,word,文档
南昌航空大学科技学院学士学位论文I毕业设计(论文)题目: 酸奶桶的反求造型研究系 别 航空与机械工程系 专 业 名 称 机械设计制造及其自动化班 级 学 号 078105304学 生 姓 名 陈烈指 导 教 师 于斐二 一 一 年 5 月南昌航空大学科技学院学士学位论文II酸奶桶的反求造型研究学生姓名:陈烈 班级:0781053指导老师:于斐 摘 要: 本文提出如何利用 UG 和 surfacer 软件进 行模具逆向设计的问题,这一问题的提出基于以下原因:1.在三坐标测量机上能够快速精确的测量到大量的已有产品的表面坐标值。2.在专用的点处理软件 surfacer 上能够较精确的将测的的点拟合成曲线和曲面。3.在 UG 软件上能够复原产品实体,以及进一步反求模具的逆向设计和制造一体化。点云数据预处理和曲线曲面重构是逆向工程模具设计中的关键技术,虽然 UG 软件具有强大的曲线曲面造型功能,但是点云数据预处理的功能相当薄弱。为此本文以surfacer 作为中间软件,完成点云数据的预处理,提高了在 UG 软件上进行逆向工程的效率和精度。本文主要研究的工作如下:1.探讨三坐标测量的多种方法和目前国内外的发展现状。2.点云排序方法的研究,初步建立点云之间的拓扑关系,使点云具有一定的完整性,并去除噪声点。3.利用 surfacer 开发工具完成点云排序与精简和点云曲线曲面拟合,并实现了拟合曲面在 UG 界面上的显示。4.以 UG 的曲面处理和实体建模作为工具软件复原实体和反求模具。关键词:逆向工程, 点云处理, surfacer指导老师签名:Reverse yougurt shape of a barrelStudent name:Chen lie Class:0781053南昌航空大学科技学院学士学位论文IIISupervisor:Yu FeiABSTRACT: This paper presents how to use UG and surfacer software on the reversing design of the mold problem, the issue raised for the following reasons: 1. In the CMM we can be able to quickly and accurately measuring a large number of products already on the surface coordinates. 2. Points in a dedicated software surfacer can be easily handled more accurate will be adjacent to the point of curves and surfaces. 3. UG software products to be able to recover entities, and to further reverse the reverse die design and manufacturing integration. Point cloud data and pretreatment of surface reconstruction is the reverse engineering of key technologies, while UG software has powerful features of surface modeling, but the point cloud data pre-processing functions quite weak. Surfacer to this paper as an intermediary software, the completion point cloud data preprocessing, the increase in the UG reverse engineering software on the efficiency and accuracy. This paper on the work are as follows: 1.The CMM on a variety of methods and the development of the status at home and abroad. 2.Point cloud sort of way, the initial establishment of point cloud relations between the topology, to a certain point cloud the integrity and remove noise points. 3.Surfacer use development tools to sort and the completion point-to streamline and point-fitting curves and surfaces, and to achieve a fitting surface interface displayed on the UG. 4.UG to the surface processing and modeling software as a tool for physical rehabilitation and reverse model. KEY WORDS: Reverse engineering, Point cloud processing, Surface Signature of Supervisor: 南昌航空大学科技学院学士学位论文1目 录摘 要 .(I)ABSTRACT.(II)目 录 .(1)前 言 .(1)1 绪论 .(3)1.1 逆向工程概述 .(3)1.2 逆向工程及模具设计的发展现状 .(6)1.3 本文研究的内容和意义 .(8)1.3.1 研究内容 .(8)1.3.2 研究意义 .(8)2 产品表面坐标的测量 .(9)2.1 测量方法分析 .(9)2.1.1 接触式测量 .(10)2.1.2 非接触式测量 .(10)2.2 测量设备的发展 .(10)2.2.1 坐标测量机的最新发展 .(11)2.3 ATOS 扫描仪数据点测量原理 .(11)2.4 点云数据的获取 .(11)3 点数据的 预处 理 .(12)3.1 surfacer 软件介绍 .(12)3.2 点云数 据预处理 1.(13)3.2.1 数 据平滑 .(13)3.2.2 数据过滤 .(13)3.2.3 数据分块和数据融合 .(13)3.2.4 数据 优化 .(14)南昌航空大学科技学院学士学位论文23.2.5 点 云拼合 .(14)3.3 曲线重构 的原理 .(14)3.4 曲面重 构的原理 .(15)4 Surfacer 软件 重构曲面 2.(17)4.1 点云数据处理 .(17)4.1.1 数据点的导入 .(17)4.1.2 噪 声点处理 .(18)4.2 曲线创建 .(18)4.3 曲面 创建 .(20)5 UG 反求 实体及模具 .(21)5.1 UG 软件 简介 .(21)5.2 UG 复原实 体设计过程 .(21)6 UG 注 塑模具设计 .(29)结 论 .(36)参考文献 .(37)致 谢 .(38)南昌航空大学科技学院学士学位论文1前 言逆向工程(Reverse Engineering,RE),也称为反求工程、反向工程、三坐标点测绘、抄数等。是指在没有设计图纸或者设计图纸不完整以及没有 CAD 模型的情况下,按照现有零件的模型(产品原型或油泥模型),利用各种数字化技术及 CAD 技术重新构造 CAD 模型而克隆或创造实物产品的过程。作为一种新产品开发和消化、吸收先进技术的重要手段,逆向工程技术结合 UG 软件的强大功能改变了传统产品设计开发模式,大大缩短了产品开发的时间周期,提高产品研发的成功率,尤其对那些形状复杂的产品更为有效。逆向工程为新产品的开发提供了技术支持,使得企业在市场上的竞争力大大提高。本文通过瓶的注塑模具的设计,说明应用逆向工程技术和三维设计软件在逆向产品的研发中的流程。本次设计根据逆向工程的技术流程,应用 AT0S 三维扫描仪对工件瓶体进行扫描获取样件表面“点云”数据;使用逆向工程专业软件 Surfacer 处理测量获得的散乱“点云”数据,并拟合曲线及曲面,进行相应的编辑修改等,使之达到精度要求;并在 UG 软件中进行产品完整曲面模型的生成以及实体化,最后生成不规则外形曲面的全部特征并得到完整产品零件模型后再生成注塑模具。结果表明,利用逆向工程技术进行产品快速逆向设计是有效的、可行的。而且此方法可以大大提高模具设计效率,降低产品开发成本。本文根据逆向模具设计的流程,分四个模块重点介绍逆向模具设计的过程,并结合工件实例介绍逆向模具设计的方法、操作、技巧以及应用,本说明书共分 6 章,具体内容安排如下。第 1 章作为绪论,介绍逆向工程的概述,目前发展状况,以及本文的研究内容和意义。通过本章的学习可以对逆向工程做一个大体的了解。第 2 章介绍产品表面坐标的测量,逆向工程的基础就是完整的点云数据,通过本章可以了解点云数据的测量方法以及所用测量设备的发展。以及重点介绍本次所用测量设备 ATOS 扫描仪的结构及工作原理。第 3 章介绍点云的处理方法,包括点云的对齐定位,噪声点的去除,数据的平顺和优化。介绍曲线重构和曲面重构的原理。第 4 章介绍 surfacer 软件常用功能命令,结合实例介绍点数据处理,曲线拟合,曲面重建的具体操作方法。南昌航空大学科技学院学士学位论文2第 5 章对 UG 软件做简单介绍并利用 UG 实体建模模块结合实例介绍曲面抽够实体的具体方法。第 6 章介绍 UG 软件的 Moldwizard 4.0 注塑模具向导模块,并详细介绍生成工件注塑模具的具体方法。本次设计说明书结合 Surfacer 和 UG 的优势重构过渡面,Sufracer 在点云数据处理、曲线构建和曲面构建有较强的优势,但在 UG 中生成过渡面的效果明显要好一些,本文结合 Surfacer 和 UG 三维造形和设计处理软件,根据优势互补原则实现曲面重构,在控制精度的前题下,使最后输出的曲面模型很好的满足了设计要求构建出比较光滑的过渡面。填补在 UG 和 Sufracer 中均可构建,但通常都会出现明显接痕或过渡不自然等现象,此设计方法必将推动模具事业的进一步发展。本设计说明书在各位来时的指导些独立完成,在此对提供帮助的所有人表示感谢。南昌航空大学科技学院学士学位论文31 绪论1.1 逆向工程概述21 世纪的设计和制造不但要面向集成化智能化标准化柔性化而且要实现并行化、分布化、网络化、虚拟化,而这一切的基础是信息的数字化。完成设计信息数字化建模的计算机辅助设计(CAD)作为一项重要的单元技术发挥着基础与核心的作用。可以说,随着参数化特征造型技术的发展,目前一般的用于正向设计的机械 CADC/AM得到了很好的解决。但在许多特殊领域,利用普通的造型手段往往难以很好的解决问题,因而迫切需要造型方法、设计手段的丰富和发展。例如,在汽车工业,新车型的外形设计仍然经常要制作全尺寸的木质或薪土模型,因为要在二维的尺寸大大缩小了的计算机屏幕上完成这样高要求的三维复杂外形设计是非常困难的。当实物模型制作好以后,就需要根据实物建立其数字化模型。模具快速制造、三维服装设计、玩具设计、电影特技动画制作、艺术制作、动植物模拟、医疗诊断、人体器官复制、地理地形测量与数字化再现等也都给设计和造型手段提出了新的课题和挑战,但同时也为几何造型技术提供了更广阔的发展空间。逆向工程是数字化与快速响应制造大趋势下的一项重要技术,是 CAD 领域中的一个相对独立的范畴。目前有关逆向工程的研究和应用大多数针对实物模型的几何形状的反求,在这个意义下,逆向工程是根据已有实物模型的坐标测量数据,重新建立实物的数字化模型,而后进行分析、修改、快速原型制造和数控加工等。这里的实物模型可以是机械产品、人体、动植物、艺术品、地形地貌等等。通过实物模型产生其数字化模型,可以充分利用数字化的优势,提高设计、制造、分析的质量和效率,并适应智能化、集成化、并行化、网络化的产品设计制造过程中的信息存储与交换。逆向工程将现代坐标测量设备作为产品设计的前置输入装置和原型或产品制造后的检测手段,与快速原型制造、CAD/CAM 相结合并形成产品设计制造的闭环系统,将有效提高产品的快速响应能力,丰富几何造型方法和产品设计手段,其关键技术可用于其他许多领域,从而拓宽计算机辅助建模的应用领域。逆向工程的应用可以归纳为以下几个方面: 【10】(1)由于种种原因,有时在只有样件,没有样件图形文档的情况下需要对样件进行有限元分析、备件加工、模具制造或者需对样件进行修改,考察修改后的样件与其他零件之间的装配协调性等等,这都需要利用逆向工程的手段将实物模型转化为CAD 模型从而提高设计制造的自动化程度。南昌航空大学科技学院学士学位论文4(2)在汽车外形设计、玩具设计、艺术品造型等复杂而且对外形美学要求较高的产品设计中,用目前普通的 CAD 软件,还很难满足形状设计的要求,一般要首先制作实物模型,然后通过测量设备输入到计算机辅助系统中,以便进一步进行设计修改和后续的各种操作。(3)逆向工程在单件产品快速定制生产中也可以发挥其独到的作用。(4)在医学领域,利用层析 x 射线(ComputeriZedTomography,CT)及核磁共振(MagnetiCReSOnnaCemIgaing,MR 工)等设备采集病变部位的外形数据,然后进行三维数字化模型重建,可以为疾病的确定与诊断提供重要依据。另外,通过对患者骨骼、关节、牙床等的测量,建立相应的计算机模型,可以使假肢制造、牙齿镶复更加具有针对性,更符合具体患者的需求。(5)在地理信息领域,利用现代的卫星遥感测量技术,对大地遥测数据进行特征识别核建模,可以建立三维数字化真实感地形图,快速生成导弹目标的自适应跟踪轨迹等。利用声纳测量设备,可以获得海底及港口的地下形貌数据,利用几何模型重建技术,将十分有利于资源利用、海底作业、海上交通、港口建设等。(6)将逆向工程与快速原型制造(RPM)相结合,组成产品设计、制造、检测、修改的闭环系统,实现快速的测量、设计、制造、再测量修改的反复迭代,高效率完成产品的初始设计。将逆向工程与快速原型制造相结合,还可以将三维物体方便可靠地“读入” , “传输” ,并在异地重新生成,即实现所谓的“三维传真” 。(7)逆向工程的另一重要应用领域是计算机辅助检测。成品的精度检测是企业进行质量控制的重要手段,然而复杂形状产品的检验往往非常困难,需要大量的时间和人力。利用自动测量设备,可以快速采集到零件的大量数字化点,将这些坐标点读入计算机,就可以通过软件自动分析测量到的数据点与理论模拟的误差。分析结果可用报告形式输出,也可以在理论模型上绘制误差彩色云图(即用不同的颜色标识不同的误差值),使零件各个部位的制造精度一目了然。其中逆向工程应用流程图如下: 【4】南昌航空大学科技学院学士学位论文5产品样件数据采集系统RE 产 品建模系统CAD/CAM系统最终产品 RP 设备样品 评价修改PDM1.2 逆向工程及模具设计的发展现状逆向工程 RE(Revere Engineering) 也称为反求工程,是基于 NURBS 的曲线、曲面重构进行研究,以现代设计理论、方法、技术为基础,运用各类专业人员工程设计的经验、知识和创新思维,对已有新产品进行解剖、深化和再创造,是已有设计的再设计,是应用于产品开发和仿真制造的一种并行设计开发系统。逆向工程是机械设计与制造应用领域的一个重要分支,在产品设计和开发中利用逆向工程可以大地缩短产品的开发周期和开发费用。随着计算机技术在制造领域的广泛应用,特别是数字化测量技术的迅猛发展,基于测量数据的产品造型技术成为逆向工程技术关注的主要对象。逆向工程是从实物样件测得的数据,经过数据预处理、曲线曲面拟合、实体模型重构等,关键技术,得到实物样件的三维 CAD 模型,继而将这些模型用于产品的分析和制造。根据逆向工程的技术流程,利用现有的软硬件设施,完成了零件及数据点的测量、数据处理、曲线曲面重构和实体建模,探讨了利用逆向工程技术进行产品快速逆向设计的可行性。实现了由实体模型到数字化 CAD 模型的快速转换,能够得到高质量的工程 CAD 资料,便于设计、加工模具。逆向工程在模具行业应用的研究,必将推动模具制造业的进一步发展模具是生产各种工业产品的重要工艺装备,随着塑胶工业的迅速发展以及塑胶制品在航空、航天、电子、机械、船舶和汽南昌航空大学科技学院学士学位论文6车等工业部门的推广应用,产品对模具的要求越来越高,传统的模具设计方法已无法适应产品更新换代和提高质量的要求。电脑辅助工程(CAE)技术已成为塑胶产品开发、模具设计及产品加工中这些薄弱环节的最有效的途经。同传统的模具设计相比,CAE 技术无论在提高生产率、保证产品质量,还是在降低成本、减轻劳动强度等方面,都具有很大优越性。美国上市公司 Moldflow 公司是专业从事注塑成型 CAE 软体和谘询公司,自1976 年发行了世界上第一套流动分析软体以来,一直主导塑胶成型 CAE 软体市场。近几年,在汽车、家电、电子通讯、化工和日用品等领域得到了广泛应用。利用 CAE 技术可以在模具加工前,在电脑上对整个注塑成型过程进行类比分析,准确预测熔体的填充、保压、冷却情况以及制品中的应力分布、分子和纤维取向分布、制品的收缩和翘曲变形等情况,以便设计者能尽早发现问题,及时修改制件和模具设计,而不是等到试模以后再返修模具。这不仅是对传统模具设计方法的一次突破,而且对减少甚至避免模具返修报废、提高制品质量和降低成本等,都有着重大的技术经济意义。 塑胶模具的设计不但要采用 CAD 技术,而且还要采用 CAE 技术。这是发展的必然趋势。注塑成型分两个阶段,即开发/设计阶段(包括产品设计、模具设计和模具制造)和生产阶段(包括购买材料、试模和成型) 。传统的注塑方法是在正式生产前,由于设计人员凭经验与直觉设计模具,模具装配完毕後,通常需要几次试模,发现问题后,不仅需要重新设置工艺参数,甚至还需要修改塑胶制品和模具设计,这势必增加生产成本,延长产品开发周期。采用 CAE 技术,可以完全代替试模,CAE 技术提供了从制品设计到生产的完整解决方案,在模具制造之前,预测塑胶熔体在型腔中的整个成型过程,帮助研判潜在的问题,有效地防止问题发生,大大缩短了开发周期,降低生产成本。近年来, CAE 技术在注塑成型领域中的重要性日益增大,采用 CAE 技术可以全面解决注塑成型过程中出现的问题。而逆向工程更是集成了模具设计的基础,采用逆向的设计思路,根据现有的产品快速创建模具,大大节省了模具设计的时间,节约了设计成本,提高了产品制造的效率。1.3 本文研究的内容和意义1.3.1 研究内容所谓逆向工程技术,是指用一定的测量手段对实物或模型进行测量,根据测量数据通过三维几何建模方法重构实物的 CAD 模型的过程。逆向工程技术与传统的正向设计存在很大差别。而逆向工程则是从产品原型出发,进而获取产品的三维数字南昌航空大学科技学院学士学位论文7模型,使得能够进一步利用 CAD/CAE/CAM 等先进技术对其进行处理。不同之处在于设计的起点不同,相应的设计自由度和设计要求也不相同。 一般来说,产品逆向工程包括形状反求、工艺反求和材料反求等几个方面,在工业领域的实际应用中,逆向工程在机械设计方面常用在新零件的设计,主要用于产品的改型或彷型设计。已有零件的复制,再现原产品的设计意图。损坏或磨损零件的还原。数字化模型的检测,例如检验产品的变形分析、焊接质量等,以及进行模型的比较。其设计流程如下 【6】 :本次毕业设计是瓶为例,通过三坐标测量机测量的近 6 万个外形数据点,根据逆向工程的设计思路,制作吹塑模具,并生成模具的工程图。1.3.2 研究意义逆向工程是一项开拓性、实用性和综合性很强的技术,逆向工程技术已经广泛应用到新产品的开发、旧零件的还原以及产品的检测中,它不仅消化和吸收实物原型,并且能修改再设计以制造出新的产品.逆向工程技术为快速设计和制造提供了很好的技术支持,它已经成为制造业信息传递的重要而简洁途径之一。逆向工程的整个实施过程包括了测量数据的采集处理、CADCAM 系统处理和融入产品数据管理系统的过程。其中在 RE 产品建模系统中实现了数据预处理、曲线曲面拟合等。从理论角度分析,逆向工程技术能按照产品的测量数据建立与现有 CADCAM 系统完全兼容的数字模型,这是逆向工程技术的最终目标。实现逆向过程后,通过 UG进行实体整合,制造出实体玩具模型,通过实体模型反求玩具的制造模具。工件模型 非接触式扫描 接触式测量 点群资料坐标点群CAD 资料与点群资料误差比对建构工程CAD 资料点资料后处理后续模具加工应用南昌航空大学科技学院学士学位论文82 产品表面坐标的测量2.1 测量方法分析2.1.1 接触式测量 【5】接触式测量精度较高,发展时间较久,机械结构稳定,讯号读取较非接触式测量设备稳定,外界干扰较小通常可校正到某一坐标系,不需经软件再次定位一次,适合量测简单几何形状物体,量测速度比较快,如单一片面,对于复杂片面则相反,北侧物体外形及颜色影响不大,同时可测量死角区域,另外不必考虑被测物体表面反光,因此应用非常广泛,但是接触式测量也存在很多缺点,其测量速度较慢,逐点方式测量,耗时较久,测量时需要设定量测基准点,需使用特殊夹制工具,例如针对不同测量物体,因侧提高测量成本,在测量时,测头需接触工件而造成测头磨损,但为了维持一定得测量精度,必须经常校正测头,有时不当的操作容易损坏某些部位的表面精度以及探头本身,一些内部元件如内圆之检验有先天的限制存在,也就是要用接触式探头检查元件的尺寸,接触式探头的直径必定要小于被测元件的大小,测头移动时并非得到接触点位置坐标而是测头球心的位置,所以需要以软件对测量数据点进行计算补正,在侧头移动时无法克服物理惯性,无法即时停止,造成测量误差,尤其是针对接触式测量设备。2.1.2 非接触式测量非接触式测量精度较差,大部分由三角测距的方式计算点资料坐标,误差值较接触式大,非接触式的量侧设备是以光学测头读取镭射光,光栅,若物件外观会反光,则造成两侧干扰,易受工件表面的反射性影响,如颜色材质等,通常将会反光的量侧物体喷涂白色涂料减少光线散射。或者多数在不受光源影响的环境下量测。非接触式测量较难针对几何形状做完美的测量,对于不连续及起伏变化较大的形状较难处理,测量时,测头量测角度要尽量垂直于被量测物体表面,易提高量测的质量,但是非接触式测量可以做到接触式测量无法应用的范围,例如人体外形的扫描,开发更多的符合人体工程学的产品,因此结合两种测量的有点,逆向工程人员一般搭配两种测量使用。2.2 测量设备的发展现代精密测量技术是一门集光学、电子、传感器、图像、制造及计算机技术为一体的综合性交叉学科,涉及广泛的学科领域,它的发展需要众多相关学科的支持。在现代工业制造技术和科学研究中,测量仪器具有精密化、集成化、智能化的发展南昌航空大学科技学院学士学位论文9趋势。三坐标测量机(CMM)是适应上述发展趋势的典型代表,它几乎可以对生产中的所有三维复杂零件尺寸、形状和相互位置进行高准确度测量。发展高速坐标测量机是现代工业生产的要求。同时,作为下世纪的重点发展目标,坐标测量机以及图像识别测量技术必将的到广泛的研究和发展。2.2.1 坐标测量机的最新发展 三坐标测量机作为几何尺寸数字化检测设备在机械制造领域得到推广使用,而科学研究和机械制造行业的技术进步又对 CAM 提出更多新的要求,作为测量机的制造者就需要不断将新技术应用于自己的产品以满足生产实际的需要。其主要的技术要求如下三个方面。 1.1 误差自补偿技术 德国 Carl Zeiss 公司最近开发的 CNC 小型坐标测量机采用热不灵敏陶瓷技术(Thermally insensitive ceramic technology) ,使坐标测量机的测量精度在17.825.6范围不受温度变化的影响。国内自行开发的数控测量机软件系统 PMIS包括多项系统误差补偿、系统参数识别和优化技术。 1.2 丰富的软件技术 Carl Zeiss 公司开发的坐标测量机软件 STRATA-UX,其测量数据可以从 CMM 直接传送到随机配备的统计软件中去,对测量系统给出的检验数据进行实时分析与管理,根据要求对其进行评估。依据此数据库,可自动生成各种统计报表,包括 X-BAR&R 及 X_BAR&S 图表、频率直方图、运行图、目标图等。美国 Brown & Sharp 公司的 Chameleon CMM 测量系统所配支持软件可提供包括齿轮、板材、凸轮及凸轮轴共计 50 多个测量模块。日本 Mitutoyo 公司研制开发了一种图形显示及绘图程序,用于辅助操作者进行实际值与要求测量值之间的比较,具有多种输出方式。 1.3 系统集成应用技术 各坐标测量机制造商独立开发的不同软件系统往往互不相容,也因知识产权的问题,这些工程软件是封闭的。系统集成技术主要解决不同软件包之间的通信协议和软件翻译接口问题。利用系统集成技术可以把 CAD、CAM 及 CAT 以在线工作方式集成在一起,形成数学实物仿形制造系统,大大缩短了模具制造及产品仿制生产周期。2.2.2 图像识别测量技术 随着近代科学技术的发展,几何尺寸与形位测量已从简单的一维、二维坐标或南昌航空大学科技学院学士学位论文10形体发展到复杂的三维物体测量,从宏观物体发展到微观领域。被测物体图像中即包含有丰富的信息,为此,正确地进行图像识别测量已经成为测量技术中的重要课题。图像识别测量过程包括:(1)图像信息的获取;(2)图像信息的加工处理,特征提取;(3)判断分类。计算机及相关计算技术完成信息的加工处理及判断分类,这些涉及到各种不同的识别模型及数理统计知识。 2.3 ATOS 扫描仪数据点测量原理德国 GOM 公司生产的 ATOS 光学三坐标测量系统(AdvancedTopometricSensor 高级外形测量传感器),由传感器(两个 CCD 相机、一个光源(卤素灯)、系统计算机、三角架组成,见图 1。传感器头安装在一个可以绕着被测物体自由运动的三角架上,在测量时传感器头可以绕着被测物体任意运动。ATOS 测量系统的数据获取方法为:首先由光源(卤素灯)产生编码光栅,这些光栅投影到被测样件表面产生一系列图象,这些图象被 CCD 相机摄取到,然后通过图象处理方法分析这些图象,计算被测样件表面点的空间位置。由于它能够采集大量样件表面的数据点,点密度高达每张照片40 多万点;也能够达到较高的精度(0002002arm);而且扫描速度高,每幅照片只需数秒。因此,ATOS 被广泛地应用于制造业的逆向工程中。 【3】2.4 点云数据的获取点云的采集可分为接触式的和非接触式的。接触式量测的优点是:精度高;快速量测基本几何体,不受量测环境、实体的材质、颜色的影响;可量测光学仪器无法量测的死角如深沟、小凹槽、倒勾等区域。其缺点是:速度较慢;必须使用特殊的夹具,提高了测量成本;需要经常校正测头等。非接触式量测的优点是:量测速度快;可以量测物件上大部分的特征;需测头补正;可量测接触式无法测量的物体,例如软质物件、塑料薄件等。其缺点是:量测精度较差;量测点云质量受外部因素的影响;较难对几何形状做完美的测量,如薄彀厚肉、凹孔等。在实际三坐标测量南昌航空大学科技学院学士学位论文11时,应该根据测量对象的特点以及设计工作的要求确定合适的扫描方法并选择相应的扫描设备。为了获得高质量的点云,本次毕业设计工件为油桶,外形硬质且较简单,故采用三坐标测量设备的接触测量方法,测得外形的三坐标数据。3 点数据的预处理3.1 surfacer 软件介绍Surfacer 是采用由点到线、线到面流程的专业逆向工程软件,它采用独一的OEP (One EntityProcessing)运算,将一笔包含数以万计的点云视为一个单一元素,因此能够同时读人多笔大量的点云资料|3 ;它强大的点云编辑工具对于较大数据点云的处理非常方便,能够对点云进行排序、取样、光顺、三角网格化等多种操作,同时使用者可以根据点云的曲率、剖面、颜色、边界快速方便地获取特征点云,便于建构 CAD 模型。相对于其他点云处理软件,Surfacer 具有多种点云对齐工具,利用此工具能够将多次测量的点云拼合在一起,误差量将达到最小。同时它提供了多种曲线生成、编辑和检测工具,根据检测出来的点云与曲线的误差以及曲线曲率的连续性,动态编辑、调整曲线来保证曲线品质。它的曲面工具与曲线工具类似。Surfacer 能够读取多种格式的文件,通过 IGES 格式文件与 CADCAM 软件交换文档。此软件的功能很强大,用户可以根据经验,将其作为开发平台,快速建构高品质的CAD 模型。Surfacer 软件主要用来做逆向工程,它处理数据的流程遵循点一曲线一曲面的原则。目前,在逆向工程中,主要有 3 种曲面构造的方案:(1)以 B。Sphne 或NURBS 曲面为基础的曲面构造方案;(2)以三角 Bezier 曲面为基础的曲面构造方案;(3)是以多面体方式来描述曲面物体,在 Surfacer 中,采用 B 样条曲线来构造曲面。对模具实体进行测量后形成的是一系列空间离散点,对这些离散点进行判断和预处理后,应用计算机辅助几何设计的有关技术,根据每个曲面的特性,构造出原型的CAD 模型。在点的处理、曲线的处理和曲面处理的整个过程中,可以用 Surfacer 软件提供的各种诊断方法来保证精度。Surfacer 支持一般通用格式如 IGES,ASCILL,VDA,DXF,STL 等并支持许多种量测设备输出的标准格式。3.2 点云数据预处理 1通常把三维空间中的点集称为“点云”或“点群” 。最小的“点云”只包含一个点,高密度“点云”可达数百万个数据点。由于曲线曲面建构方法多种多样,对测量南昌航空大学科技学院学士学位论文12数据质量、数量、密度及组织形式方面的要求不尽相同,故需要对原始测量数据进行预处理。3.2.1 数据平滑数据测量得到的往往是以散乱点形式无序排列的大量点云。由于实际测量过程中受到种种人为或随机因素的影响,使得测量结果不可避免地引入了“噪声” 。为了降低或消除噪声对后续建模质量的影响,有必要对测量得到的“点云”进行噪声消除与平滑滤波。数据平滑通常采用标准高斯、平均或中值滤波算法。高斯滤波器在指定域内权重为高斯分布,其平均效果较小,故在滤波的同时能较好地保持原数据的形貌;平均滤波器采样点的值取滤波窗口内各数据点的统计平均值;而中值滤波器采样点的值取滤波窗口内各数据点的统计中值,这种滤波器消除数据毛刺的效果较好。实际使用时,可根据“点云”质量和后续建模要求灵活选择滤波算法。3.2.2 数据过滤测量获得的数据十分巨大,如果不进行必要过滤以滤除冗余点云,处理起来仍然十分复杂。因此,数据过滤是数据处理中的一个必要环节。进行滤除点云的工作在基于褓结构允许的误差范围内进行。通常的滤除方法有空间滤除法、自适应滤除法等。通过数据过滤,可以使数据大量减少。3.2.3 数据分块和数据融合即使经过点云的过滤,但对于特别复杂、曲率变化过大的实体,过滤后的点云数据量还是比较大,一般的CAD/CAM 软件,处理起来还是比较困难,不但不能保证精度,花费的时间也相当可观。这就失去了逆向工程快速响应市场变化的特点。故有时应考虑对整体点云进行分块,将其分割成一块块小的点云数据后进行处理,最后再进行整体匹配恢复原始实体形状。进行点云分块时,应基于方便最后整体匹配的原则,使分割线界于曲率平滑处,在曲率变化大的地方避免分割线的介入,否则匹配时容易引起整体中局部细节的变形。分区域构造曲面片并将这些曲面片按一定的边界条件连接起来是利用测量数据建模的基本技术,因此,分块和融合是对“点云”进行的基本操作之一,可通过自动或人工干预的可视化交互方式进行。人工干预方式下,数据分块或融合取决于操作者对后续建模方法的理解和实际操作经验。3.2.4 数据优化这种操作的主要目的是为了获得不同形态及密度的新“点云”。如按比例缩放“点云”,按要求的偏置量产生新的等距“点云”,将“点云”向某指定面投影产生南昌航空大学科技学院学士学位论文13二维投影“点云”,或进行网格化处理,将其他形式的原始“点云”转化为网格化“点云”等等。有时,实体表面曲率变化较大的地方,点云数据量相对比较少,不足以表达实体的细节信息,为充分获得实体各部分特征,应在数据滤波以及数据分割基础上做适当的数据加密处理,使最后构造的实体能够达到最小允许的误差。另外,实物经过多次测量后得到的点云一般是杂乱无章的。为了保证后面生成曲线与曲面的质量,还需要对点云进行排序优化。3.2.5 点云拼合无论是采用接触式还是非接触式的数字测量方法,希望通过一次测量完成对整个待测件的数字化工作是很困难的。通常的做法是将待测件重新定位,以另一有利的角度或者方向获取试件不同方位的表面信息,这称为视。从不同的视对待测件进行几次测量后,所得数据的局部坐标系和组织是不同的,将这些不同的数据集转化为统一的数据形式并构成整个待测件表面的完整信息,这个过程称为拼合。对同一物体的多视点云的拼合,一直有两种处理方法:一是对点进行处理,即直接对点云进行拼合,再理构出原型;二是对各视图进行局部构造几何形体,最后拼合这些几何形体。显然,若单个视图能局部地构造几何形体,并具有明显的几何特征,利用这些特征进行拼合,其速度和准确性都是显而易见的。但其缺点是,不同视图中的特征往往不一致,甚至同一个特征在其他视图中被分割成许多特征或者消失。同时该方法带来的几何图形之间的布尔运算将涉及到许多CAD 中目前尚未解决或解决不甚圆满的难题,如曲面的拼接、求交、延拓和过滤。基于点的拼合的最大优点是能对物体所求得的各个面有总体上的了解和把握,能获得拓扑上一致的数据结构。尽管该数据结构可能是庞大的,但这种一致性是基于面的拼合难以达到的。3.3 曲线重构的原理自由曲面点云数据经切割之后,应根据需要判断和决定生成哪种类型的曲线。也就是特征曲线的生成,在反求工程中,最终目标是希望生成准确度高而且光顺性好的曲线、曲面,而准确度和光顺性永远是矛盾的。由于实体原形中各特征面交界处圆角的存在,点云数据的采集不够全面,因此拟合的各个曲面之间往往存在间隙没有相交,这时候需要对曲面进行延伸操作来构建实体。由于各个构建曲线在端点处具有不同的曲率,所以曲面的延伸往往有很明显的变形,给最终的实体构造提出了难题。为了使自由曲面延展后具有较好的准确性和光顺性,本次毕业设计中采用直线拟合曲线的两端的方法来构造曲线。为了能够获得较高质量的曲线, 必须根据数据点的特点(有序的、无序的、平滑南昌航空大学科技学院学士学位论文14的、杂乱的) 来决定要生成的曲线类型。一般而言, B2Spline 曲线比较适合处理平坦的数据点, 对于不平坦的数据点 ,NURBS【6】 曲线处理结果较好。 B2Spline 曲线具有局部控制能力, 在其基函数中的定义增加了节点向Reverse Engineering in the application of product designThe application that is in expatiate contrary engineering in the product design with develop the term, effectively of solution shape design with follow-up engineering design, manufacturing link mutually the problem that become disjointed, put forward on sowing in adopt in the product design process the Pro/Designer have no with Pro/Engineer to sew to connect method, design for the industry product shape with the in the late engineering makes of linking up and developing a new path, the process of its design process is a line of for valid measure that product design systematize to provide, from but shortened the product design development, period, realizes the product shape design of systematize.1 reverse engineering of the content and scope of applicationWith the development of computer technology, CAD technology has become a product design staff an important tool for research and development, of which three-dimensional modeling technology has been widely used in manufacturing products and mould design, program evaluation, automated processing and management of all aspects of maintenance. In the actual development of the manufacturing process, design staff to receive technical information may be all kinds of data types of three-dimensional model, but a lot of time, it is from the upstream manufacturers have the physical product model. Designers need to adopt a certain way, this kind of information into the CAD model, which applied to reverse engineering (Reverse Engineering). The so-called reverse engineering, refers to a means of measuring the physical model or measured, according to survey data 3D modeling methods through physical reconstruction of the CAD model of the process.Reverse engineering technology and traditional design is very positive difference. And reverse engineering is starting from a prototype and then obtain three-dimensional digital model of the product, make it possible to further use of CAD / ACE / CAM and CIMS and other advanced technology to process.In general, reverse engineering products, including the shape reverse, the summation of the anti-reverse, and several other materials, in the industrial field in the practical application, including the following: (1) the design of new parts, mainly for the product imitation or modified design. (2) Have been parts of the copy, reproduce the original intent of the design of the products. (3) damaged or worn parts of the reduction. (4) digital model of detection, for example, the deformation of product testing, welding quality, as well as a model for comparison. Reverse engineering technology for the rapid design and manufacturing provided a good technical support ,it has become an important manufacturing information transmission and concise way. And the traditional product design, market research in general, the development requirements table after the plane started to sketch the idea of forming a little integrity of the program, started drawing three-dimensional map, then completely stereotyped as required draw results map, three view or create a simple model. In the process of design, engineering and technical personnel needs, product modeling staff and workers work together, using samples physical model to express the idea of designers, but for every kind of a program have produced samples, to pay a lot of labor, There is a low accuracy, modify adjustment difficulties, the design cycle length and cost of higher issue.2 CAD technology in product design issues.The development of computer technology, brought about the third wave of technological revolution, computer-aided design (computer aided design, referred to CAD) technology is the computer industry in the area of application of the most active one. It sets numerical simulation, geometric model of processing, graphics, database management systems, and other aspects of technology integration, the abstract, flat, separation of the specific object of design, visualization, it can through the virtual reality technology The product of the shape, texture, color, and even brought process demonstrated, and can product design process, through data management, and systematic, standardized, and this is industrial design and integration of CAD technology will inevitably the basis.Reverse engineering software implementation of the conditionsAt present, relatively commonly used generic reverse engineering software Surfacer, Delcam. Cimatron to Strim. The specific application of reverse engineering system is mainly the following: Evans for the development of machine parts to identify the reverse engineering system; Dvorak development of the imitation parts of the old reverse engineering system: HHDanzdeCNC CMM system. These systems to reverse the practical problems in the design process, greatly facilitate the design staff. Besides, Some large CAD software is gradually provided for reverse engineering design module. Such as Pro / E and the ICEM Surf Pro / SCANTOOLS module can accept and orderly points (measurement line), can also accept the point cloud data. UG as other software, with versions of the increase, reverse engineering module is gradually enriched up. These software reverse engineering for the development of the implementation of the software conditions. These software and despite some relatively high-end design software, already the product of complex design and modeling exaggerated features, but the art designers to master and use of such software, so far is not an easy task. So in the structural design of the major designers who are mechanical engineers, design and way of thinking completely different from the modeling designer, their thinking is a fully consistent with the design of mechanical design standard way of thinking. So, how will the two designs in the design of the products are in combination, and receive better integrate and better processing from design to completion of the conversion process of our product design to consider the issue.3 product design - CAD reverse engineering technology(1) Pre / E of the design parameters of the projectParametric Design (Parametric) (also known as drive size Dimension-Driven) is in the practical application of CAD technology in the subject, it will not only CAD system is an interactive graphics capabilities, but also with automatic mapping capabilities. Currently, it is the application of CAD technology in the field of a major, Judai further study the issue. Use of the design parameters of the development of the means for product design system will enable designers from the large number of heavy and trivial mapping out relief work, can greatly improve the design speed, and reduce the storage of information. Parametric design, the key is to extract the geometric constraints and expression, and the parameters of constraint solving geometric model of the structure. 1988, the United States launched the first technology companies parameters of the design parameters of CAD system Pre / Engineer (referred to Pre / E) to give full expression to their common in many parts, components, the simple design of the advantages. Its main features are: Feature-based, full-size constraints, all data related to the size of drive to amend the design. So that we can use PTC: the companys industrial design software Pre / Designer (referred to Pre / D) of surface design, the Pre / D and Pre / E is using the same database, is the seamless connection between the two, thus Design modeling designers and structural engineers can better collaboration(2) Pre / D surface design capabilities for industrial designers and those who want to build surface model for the engineering staff, Pre / I is precisely the tools they need, Pre / D can build high-quality free surface model, and Can easily switch to the other based on the manufacturing engineering CAD system. Pre / D to create a true and accurate geometry, the use of the more easily it can create a model to shorten the design cycle. Pre able to use visual aesthetic requirements and die manufacturing process in the engineering requirements combined with a very good, this point in the creation of free surface model now in the process was particularly notable.(3) Pre / D and Pre / E of the rumored pumped Pre / Designer and Pre / Engineer data exchange between There are two ways: one is with the Pre / Engineer direct exchange of data and another is a way to document and the Pre / Engineer data exchange. (4) three-dimensional modeling complex product design for the CAD application form decorative strong, especially products containing complex surface, you can use the Pre / D and Pre / E combination, modeling designer in the Pre / D inside do ID, so Surface modeling, directly from the Pre / I started in the Pre / E, the data lead to the Pre / E designers from the structural design of the structure of the entire design process of structural design or even all done, the customers request or designer Local to the program to make changes, then only in the Pre / D changes inside, to better keep good again after the original name given to Pre / E, then Pre / E has also been changed, but do not have to redo the structure (of course, to amend For structural conditions for the existence of, the father of characteristics that it will not be a problem).Over the years, the development of the traditional industrial products are to follow strict form of research and development process: from the idea of demand for products, features and specifications of the expected target identification, then to the various components for the design, manufacture, assembly, testing performance. Each component is retaining the original design, the design usually to CA in the form of documents to save. This development model known as scheduled mode (Pre-scriptive Model), the development of such projects also known as positive work (Forward Engineering). However, with the level of industrial technology upgrading and improving the standard of living, Any GM products in the consumer demand for high-quality, functional needs of the market has ceased to be competitive to win the only condition. Products not only to advanced features, and more focused on modeling the appearance of products, this is not the traditional mechanical engineers to the competent. Designers to shape the way through the manual model, for example: wax model, wood model, cast, clay model, engineering plastics, etc.-and then three-dimensional measurement methods generate free surface of the CAD file, which is the so-called Reverse engineering (Reverse Engineering, RE). Then put in front of the designer and manufacturer of the physical kind, will need physical model into a CAD model, as product information model is the realization of CAD / CAM technology seamlessly create the key.Reverse Engineering (Reverse Engineering) in the absence of design drawings or design drawings incomplete and not the CAD model and in accordance with the existing parts of the model (or sludge prototype model), the use of digital technology and CAD technology re-structure the CAD model And cloning to create physical products or processes. Project is positive from the CAD model to the physical model into the process, and reverse engineering is from the physical model to the CAD model of the transformation process, both the design process just the opposite, reverse engineering and forward the application of different areas, with the Digital measurement of the rapid development of technology, reverse engineering in the manufacturing sector of the increasingly widespread and mature, on the reverse engineering of CAD has also become one of the hot areas of research.4 modeling technology, including reverse engineering from the measurement data to the CAD model of a set of technical steps can be summed up in the following several aspects of key technologies: (1) measurement data processing - As the number of measurement equipment by the wider use of massive data point (in millions of orders of magnitude) access to a very easy matter. 1000000 data regardless of the person or read data, and other aspects of reconstruction model for us is very inconvenient, and in need of reconstruction CAD model before the measurement data pretreatment. (2) grid model construction three grid model of reverse engineering is commonly used in the model that way. three grid model can easily express complex shape of the objects surface, while grid model for the reconstruction surface model is a very good foundation model. (3) basic model surface structure - reverse engineering modeling is the ultimate goal of universal CAD system to provide a valuable basic surface model, in the final completion of GM products in the CAD system model of reconstruction. So reverse engineering of the basic surface model for the Reconstruction of high-quality reconstruction of the CAD model is very important. (4) model of quality - reverse engineering model is based on measurement data in the reconstruction CAD model. In the reconstruction process because of the various data (such as compression) so that data back to the inevitable errors. The ultimate CAI model is in error to allow the evaluation of the accuracy of reconstruction is an important indicator of the quality of model one. Following this will be a few aspects of the systems described.4.1 Data pretreatment technology Now with three-dimensional scanning equipment development, the measurement data are also increasing the number of points, with millions of data points measured in the paper is already very common. So many data points, the benefits are obvious, able to model all the characteristics of the small acquisition, but processing system, it is a lot of obstacles. This will not only greatly increase the systems capacity, but also reduces efficiency, which will affect the whole process of reverse engineering modeling. Therefore, the measurement data pretreatment reverse engineering modeling now become an important aspect of technology. Survey data preprocessing, in addition to the large amounts of data compression, but also to remove the noise generated in the scan data. No matter how advanced measuring equipment, the impact of noise is always inevitable. Although not much noise points, but the impact of noise or great, the work of removing the noise generated model can greatly improve the quality. Because the shape of certain models more complicated, often unable to get a scan all the data. In this way, a model of the measurement data have many pieces, so in model building, must be multi-block data connection, integration into a model. The process works in reverse as in the Register, that is re-positioning data.4.2 grid model construction Grid model in the reverse engineering of a wide range of applications. Measured data points we generally referred to as point cloud. Point cloud data does not include any topology information, in order to reconstruction surface model and rapid prototyping (Rapid Prototype Manufacture, RPM), and other processing needs we need to point cloud data constructed on the basis of triangular grid model. 1.30 Mesh topology contains a wealth of information that can be used, such as special Reconstruction of the levy, such as surface divided post-processing Club. grid can also show a real model of the shape, can achieve good visual effects. In addition, the triangle enough detailed grid can be directly used for processing parts. According to deal with the object and the use of different measuring techniques and tools, reverse engineering CAI modeling content can be divided into two aspects: one is to examine the entire body of CAD modeling, the other to deal with a complex of the main characteristics of CAD surface modeling. It also determines the triangular grid model of the construction method has two main categories. The whole body of the CAI) modeling, mainly in the field of medical image visualization applications. This kind of research more and relatively deep, is generally used CI, access to facilities such as the organ section contour, and then from these contour triangular grid structure, and its main difficulty is the handling of the bifurcation and Holes The model. According outline cross-section of this structure of the triangular grid model algorithm is now very mature and can achieve high efficiency. Modeling a large number of mechanical parts, are generally dealt with rehabilitation of the surface of the CAD modeling. Many aspects of this method, but the effect is not very satisfactory, algorithms are from a seed triangle, traverse around the point, to build triangular grid. Now is the algorithm needs to be raised the efficiency and quality of the grid. Most of the triangulation method is not the original data points of the interpolation algorithm, which caused a triangular grid model with the original data points of error, this error will be accumulated up to the surface reconstruction.4.3 Surface ReconstructionFree surface model in reverse engineering products play an important role modeling, because of free-form shape of a flexible, in aviation, aerospace, automotive, mould and other industries a large number of applications, at the same time, these industries are also reverse engineering applications in important areas, based on free Surface Reconstruction has been a model of reverse engineering CAD important area of research. Surface Reconstruction (also known as surface modeling) through modeling can be separated from the measurement data for changes in the reconstruction surface, surface fitting interpolation, including surface and surface approximation, surface Interpolation demands Interpolation the surface strictly Through the data points; surface approximation is based on the data structure of a discrete surface, so that these points in some sense the most close to the surface by the structure. Based on different forms of surface topology, the common surface reconstruction in two ways. Bezier surface to 1.30 based on the tripartite domain surface construction method, and B-spline 101 NURBS surface and based on the four sides domain surface constructed. Based on the 1.30 Bezier surface of the triangular domain surface constructed. Dealing with the basic idea is to be dealt with the original number considered as a whole. First constructed in accordance with point cloud summer triangular grid and building a triangular grid, the use of 1.30 Bezier surface in the grid on the basis of constructing smooth surface 121. 1.30 Bezier surface interpolation in the triangular grid of each triangle on the initial structure of the three variables 1.30 Bezier patch, and then each triangle patch up to four bands, and then each patch for CT (clough - tocher) segmentation, and then adjust each patch of the control points, so that the entire surface to a combination of geometric order (GCI) a row.4.4 Based on the characteristics of the model reconstructionSince reverse engineering is the subject of dealing with three-dimensional space data, how the reconstruction process in the surface model and accurately reproduce the characteristics of products, reverse engineering is the product model can comprehensively CAD system in general an important symbol. Now the reverse engineering, especially in the Reconstruction of general machinery parts, one after another to automatically extract model characteristics. Not only automatically extracted from the characteristics of products, such as bevel, the transition surface, Geng Shiba based on the characteristics of the thinking of food to the various aspects of reverse engineering, reverse engineering feature extraction as a supplementary means of modeling. In the reconstruction of the main features of the redevelopment There are two ways: First, based on the characteristics of point cloud data from the second gri
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