外文翻译-夹具设计机械

1、精品 料推荐外文翻译基于事例推理的夹具设计研究与应用摘要 :根据基于事例的设计方法 ,提出采用工序件的特征信息和夹具的结构特征信息来描述夹具的相似性 ,并建立了包括这 2 方面主要特征信息为基础的事例索引码 ,设计了事例库的结构形式 ,创建了层次化的事例组织方式 ;同时 ,提出了基于知识引导的夹具事例检索算法 ,以及事例的修改和采用同族事例码进行相似事例的存贮 ,形成了基于事例推理的夹具设计 .所开发的原型系统在型号工程夹具设计等项目的设计过程中得到了应用 ,并取得了令人满意的使用效果 .关键词 : 基于事例的推理夹具设计cad夹具是以确定工件安全定位准确为目的的装置，并在加工过程中保持工件与

2、刀具或机床的位置一致不变。因为夹具的结构依赖于产品的特点和在企业规划中加工工序的地位 ,所以它的设计是制造过程中的瓶颈 , 制约着效率的提高 . 夹具设计是一个复杂的过程 ,需要有从大量的设计论文中了解质量知识的经验，这些设计论文包括工件的结构设计、涉及加工工艺，和加工环境。当用这些擅长绘制详细设计图的传统的 cad 工具（如 unigraphics、catia 、pro/e)时,这仍然是一项非常耗时的工作，但是利用以往的设计经验和资源也不能提供一些益处 ,而这正是提高效率的关键因素 . 基于事例推理 (cbr) 的方法适应以往个案解决的办法 ,建立一个新问题的方法 ,主要有以下四步骤 :检索

3、、利用、修改 ,并保留 .这是一个比用专业系统模仿人类思维有用的使用方法， 因为提出一个类似的情况 ,和采用一些修改 ,似乎不言自明 ,而且比人类更直观 .所以支持不同事例的设计工具已经在诸多领域中发展起来，如在注射成型及设计、建筑设计、模具设计投死 , 规划过程中 ,还有夹具设计 . 孙用六个数字组成代码参数 ,包括工件的形状、机械部分、轴衬 ,第一定位装置 ,第二定位装置和夹紧装置 . 但这个系统不能用于除钻床夹具外的其他夹具类型 ,不能解决储存需要保留的同一参数代码的问题 ,这在 cbr 中是非常重要的 .1 事例参数和事例图书馆的建立 1.1 事例参数事例参数应该由工件的所有的特征组成

4、，来区别不同的夹具. 使用他们能够使操作方便 . 因为零件的形状是多种多样的 , 在生产企业中制造的技术要求也不断发展 ,许多特征作被用做事例参数将会使搜索速度降低 ,其主要特征是不1精品 料推荐重要的 ,因 分配 每个特征的比重必 减少 . 另一方面 ,事例参数包含所有的特征是困 的。因此 ,考 到 和快速 的需求 ,事例参数要包含工件的主要特征和 具的 构。事例参数代 由 16 位数 成： 13 位数是事例特征 3 位数是事例 数字。前 13 位数代表 13 个特征。 每个数字与特征的一个属性相一致 , 可能是 * 、 ？ 、1 、2 ， a 、b, ，z ， ，等其中的一个。其中， *

5、是指任何一个 ,?代表不确定 ,0 代表没有。系 定 : 具的 型，工件的形状，位置模式不能是 * 和 ?。在 系统时 ,三个 目的属性信息没有 些 , 就意味着必 确定的属性。最后三位数是事例 号 ,如果事例特征的 13 位数是一 的 , 三个数字就用来区 他 。 系 定 :000是用于修正的一个典型事例 ,其他事例 001 、002 、, 些是用于 找参考事例的 . 如果其中一个偶 需要改 成典型事例 ,首先它必 要求改成 000,前面的自 成参考事例 .事例索引 的 构如 1 所示。1 具 型；6工件重量；11 模型；2工件形状；7工件 度；12 具体；3工件材料；8加工内容；13其他；

6、4批量；9 程所有物；14 到 16事例 ；5工件比例；10定位模型；图 1事例索引 的 构1.2 事例 事例 由 多 定 的事例 成。事例的描述是基于事例推理的最重要的 之一。所以由索引 复合。1.3 事例的 次化 具的 构相似被 是整个 具，成分和内容相似。所以，整个 具事例 ，成分事例 ， 具的成分事例 形成相同。整个 具的 料通常是由工件 料和工件加工 料 成 , 就意味着 具的 足特 功能的需求 .全部 具事例是由功能成分 成， 它是用功能成分的名字和数字来 行描述2精品 料推荐的。成分事例代表成员（成分功能和其他结构成分，主要驱动参数，数字，和它们的约束关系）。成分事例（夹具的最低

7、层）是功能成分和和其他成分的结构。在现代夹具设计中有很多参数化准件和普通非标准件。所以成分事例图书馆应记录特殊参数和保持它们的方法。2 事例修改的策略在基于事例的夹具设计中，最重要的是相似点的修改，这样能有助于获得最相似的事例，以及缩短适应时间。根据夹具设计的需求，事例修改的策略使最接近的事例方法和知识指导结合起来。首先在深度上查找，然后在宽度上；知识指导策略意味着在来自客观事物根源的知识规则上查找，这就要首先查找固定类型，然后查找工件的形状，第三查找定位方法。例如，如果事例索引码包括夹具类型的磨削夹具，就只查找所有的磨削夹具，然后查找工件形状的盒子，第三查找一个平面两个销的定位方法。 如果没

8、有合适的， 就查找深度标点，然后回到最上层，然后再找所有与宽度相关的事例。修改方法：1）根据夹具事例库的事例索引信息，查找有关事例库。2）将事例索引码与事例库的每个事例码匹配，然后计算相似尺寸的价值。3）整理相似尺寸的次序，最大的架子是最类似的事例。两个事例之间的相似点是基于两个事例特征之间的相似点。相似点尺寸的计算依靠特征的类型。相似点的价值可以通过数字化的价值来计算，例如比较重量分别是 50kg 和 20kg 的工件。非数字化的价值也能计算，例如，现在前13 位索引码都是非数字化的价值。一个夹具的相似尺寸的计算公式如下：其中 s 表示通用夹具的相似尺寸， n 表示索引特性数，表示每个特性的

9、重量，表示事例库中特性和相关夹具的特性的相似尺寸。同时，数值计算如下：3精品 料推荐其中表示第 i 个特征的索引特性值，表示事例库中第j 个事例的第 i 个特征的特性值。所以有两种方法选择相似夹具。 一个方法是建立数值。 如果通用事例的相似尺寸值比给定的数值小，这些事例就不能选来作相似事例。事例库最初建立的时候，只有一些事例，数值可以建小一点。如果有大量的相似事例，数值就应该建的大一些。另外一个方法是只建立相似事例的数字（例如 10），这是类型单里相似尺寸的最大值。3 事例的修改和存储 3.1 事例的修改夹具设计中相似事例的修改包括以下三个阶段：1） 成分的替代2） 保持形式不变，调整成分的特

10、性3） 模型重新设计如果夹具的成分是普通的物品，它们能通过使用工具被修改，代替以及删除，这些已经被设计好了。3.2 事例的存储在将一个新的事例保存到事例库之前， 设计者必须考虑保存是否有价值。 如果这个事例不能增加系统的知识，就没有必要把它保存到事例库里。如果它有价值的话，设计者在保存之前必须分析一下，看看这个事例是否作为标准事例或参考事例被存储了。一个标准事例是一个描述同族事例主要特征的标准。一个同族事例是有事例库中索引码前 13 位相同而最后三位不同的那些事例组成的。一个标准事例的最后三位通常是 “000”。一个参考事例属于同族标准事例，4精品 料推荐最后三位用不同数字区分。从被解释的概念

11、中，可采用以下方法：1）如果一个新的事例和任何一个存在的事例族一致，和一个存在的标准事例的前 13 位数相同，那么这个事例就不能存储因为已经这种标准事例了。 或者只能作为一个参考事例保存（最后三位不是“ 000”，而且和其它的不一样）在事例库中。2）如果一个新的事例和任何一个存在的事例族一致， 并且被认为代替这个事例族要比以前的标准事例好，那么这个标准事例就被这个新的事例代替，以前的标准事例作为一个参考事例保存。3）如果一个新的事例和任何一个存在的事例族不一致， 一个新的事例族将会自动产生，并作为标准事例保存到事例库中。4 夹具设计中基于事例推理的过程根据夹具设计的特性，夹具设计的基本信息，例

12、如夹具的名字，零件，生产和设计者等等，必须先输入。然后，输入或设计工件的模型。输入有关工件的细节信息， 建立事例索引码， 然后 cbr 开始依靠相似尺寸查找相似事例， 选出最相似的事例。 如果需要的话， 事例要满足通用性设计， 再存储到事例库中。程序流程图如图 2 所示图 2基于事例推理的夹具设计流程图5精品 料推荐5 基于事例推理的夹具设计说明这是一个工件如图 3 所示。材料是 45 钢，底座，形状为块状，生产批量为中批等。需要设计成一个用来旋转孔的旋转夹具。图 3 需要设计夹具的一个工件（最大尺寸 80mmx49mmx22mm）工件的特征值，属性值，事例索引码和重量在表1 中列出。表 1工

13、件的事例索引码和重量特征名称特性值索引码重量夹具类型车床夹具1100工件形状块状990工件材料中碳钢370批量中批260工件比例小560工件重量轻560工件刚度硬度强160加工内容孔380程序要求完成加工370定位方法三个平面1100夹紧方法不确定？90夹具体复合480其他没有0606精品 料推荐通 过 查 找 和 计 算 相 似 点 ， 最 相 似 的 事 例 的 事 例 索 引 码 是19325513321402000，细节信息在表 2 中列出。表 2最相似事例的事例索引码特征名称特性值索引码夹具类型车床夹具1工件形状块状9工件材料中碳钢3批量中批2工件比例小5工件重量轻5工件刚度硬度强1

14、加工内容孔3程序要求完成加工3定位方法三个平面1夹紧方法不确定？夹具体复合4其他没有0相似点的计算如下：所以夹具的相似尺寸值是 0.806，这是在事例库中用于设计的最相似的事例，最相似的事例的结构如图 4 所示7精品 料推荐图 4最相似的夹具当成分替代，修改定位模型和夹紧模型，以及调节相关尺寸之后，新的夹具被设计出来，图形如图 6 所示图 5需要设计的新夹具因为在事例库中没有相似夹具，新夹具被储存到事例库中。事例索引码是19325523311402000。6 结论基于事例推理， 作为一个问题解决的方法， 是一个比模仿人类思想的专业系统更有效的方法，已经在很多难获取知识的领域里得到发展。基于事例

15、推理的优点如下：它和人类的思想很相似； 一个事例库通过保存新事例获得自学能力，它比有惯例库更快更容易，它可以更好的传递和解释新的知识，这和惯例库有8精品 料推荐很大的不同。基于事例推理中提出的一个夹具设计的框架已经被实行了，使用的是支持基础数据的 vc+ ，ug 电脑绘图软件。 这个框架也已经和普通成分库和典型夹具库结合起来。这个发展的标准系统，用于航空项目，帮助夹具设计者提高设计效率和重新使用先前的设计资源。9精品 料推荐附录 2 英文原文application and developmentof case based reasoning in fixture designabstract:

16、 based on the case based designing (cbd) methodology, the fixture similarity is in two respects: the function and the structure information. then, the computer aided fixture design system is created on case based reasoning (cbr),in which the attributes of the main features of workpiece and structure

17、 of fixture as case index code are designed for the retrieve of the similar cases, and the structure and hierarchical relation of case library are set up for store. meanwhile, the algorithm based on the knowledge guided in the retrieve of the similar cases,the strategy of case adapt at ion and case

18、storage in which the case ident if cat ion number is used to distinguish from similar cases are presented. the application of the system in some projects improves the design efficiency and gets a good result .keywords: case based reasoning ;fixture design; computer aided design(cad)fixtures are devi

19、ces that serve as the purpose of holding the workpiece securely and accurately, and maintaining a consistent relationship with respect to the tools while machining. because the fixture structure depends on the feature of the product and the status of the process planning in the enterprise, its desig

20、n is the bottleneck during manufacturing, which restrains to improve the efficiency and leadtime. and fixture design is a complicated process, based on experience that10精品 料推荐needs comprehensive qualitative knowledge about a number of design issues including workpiece configuration, manufacturing pr

21、ocesses involved, and machining environment. this is also a very time consuming work when using traditional cad tools (such as unigraphics, catia or pro/e), which are good at performing detailed design tasks, but provide few benefits for taking advantage of the previous design experience and resourc

22、es, which are precisely the key factors in improving the efficiency. the methodology of case basedreasoning (cbr) adapts the solution of a previously solved case to build a solution for a new problem with the following four steps: retrieve, reuse, revise, and retain 1. this is a more useful method t

23、han the use of an expert system to simulate human thought because proposing a similar case and applying a few modifications seems to be self explanatory and more intuitive to humans .so various case based design support tools have been developed for numerous areas2-4, such as in injection molding an

24、d design, architectural design, die casting die design, process planning, and also in fixture design. sun used six digitals to compose the index code that includedworkpiece shape, machine portion, bushing, the 1st locating device, the 2 nd locating device and clamping device5. but the system cannot

25、be used for other fixture types except for drill fixtures, and cannot solve the problem of storage of the same index code that needs to be retained, which is very important in cbr6.1 construction of a case index and case library1.1 case indexthe case index should be composed of all features of the w

26、orkpiece, which11精品 料推荐are distinguished from different fixtures. using all of them would make the operation in convenient. because the forms of the parts are diverse, and the technology requirements of manufacture in the enterprise also develop continuously, lots of features used as the case index

27、will make the search rate slow, and the main feature unimportant, for the reason that the relative weight which is allotted to every feature must diminish. and on the other hand, it is hard to include all the features in the case index.therefore, considering the practicality and the demand of rapid

28、design, the case index includes both the major feature of the workpiece and the structure of fixture. the case index code is made up of 16 digits: 13 digits for case features and 3 digits for case identification number.the first 13 digits represent 13 features. each digit is corresponding to anattri

29、bute of the feature, which may be one of“ * ”, “？” , “1”, “2”, ,“a ”,“ b” , ,“ z” , ,etc. in which, “* ” means anyone, “?” uncertain, “0”nothing.the system rules: fixture type, workpiece shape, locating model cannot be“* ” or“?”. when the system is designed, the attribute information of the three it

30、ems does not have these options, which means the certain attribute must be selected.the last three digits are the case identification number, which means the 13 digits of the case feature are the same, and the number of these three digits is used for distinguishing them.the system also rules: “ 000”

31、 is a prototype case, which is used for retrieval,12精品 料推荐and other cases are“001” ,“002”, , which are used for reference cases to be searched by designers. if occasionally one of them needs to be changed as theprototype case, first it must be required to apply to change the one “to 000”, and the fo

32、rmer is changed to referential case automatically.the construction of the case index code is shown in fig.1.1.2 case librarythe case library consists of lots of predefined cases. case representation is one of the most important issues in case based reasoning. so compounding with the index code,.1.3

33、hierarchical form of casethe structure similarity of the fixture is represented as the whole fixture similarity, components similarity and component similarity. so the whole fixture case library, components case library, component case library of fixture are formed correspondingly. usually design in

34、formation of the whole fixture is composed of workpiece information and workpiece procedure information, which represent the fixture satisfying the specifically designing function demand. the whole fixture case is made up of function components, which are described by the function13精品 料推荐components

35、names and numbers. the components case represents the members. (function component and other structure components， main driven parameter, the number, and their constrain relations.) the component case (the lowest layer of the fixture) is the structure of function component and other components. in t

36、he modern fixture design there are lots of parametric standard parts and common non standard parts. so the component case library should record the specification parameter and the way in which it keeps them.2 strategy of case retrievalin the case based design of fixtures ,the most important thing is

37、 the retrieval of the similarity, which can help to obtain the most similar case, and to cut down the time of adaptation. according to the requirement of fixture design, the strategy of case retrieval combines the way of the nearest neighbor and knowledge guided. that is, first search on depth, then

38、 on breadth; the knowledge guided strategy means to search on the knowledge rule from root to the object, which is firstly searched by the fixture type, then by the shape of the workpiece, thirdly by the locating method. for example, if the case index code includes the milling fixture of fixture typ

39、e, the search is just for all milling fixtures, then for box of workpiece shape, the third for 1plane+ 2pine of locating method. if there is no match of it, then the search stops on depth, and returns to the upper layer, and retrieves all the relative cases on breadth.retrieval algorithms:1)accordin

40、g to the case index information of fixture case library, search the relevant case library;14精品 料推荐2)match the case index code with the code of each case of the case library, and calculate the value of the similarity measure;3)sort the order of similarity measure, the biggest value, which is the most

41、 analogical case.similarity between two cases is based on the similarity between the two cases. features. the calculation of similarity measure depends on the type of the feature. the value of similarity can be calculated for numerical values, for example, compareworkpiece with the weight of 50kg an

42、d 20kg. the value can also be calculated between non numerical values, for example, now the first 13 digits index code is all non numerical values. the similarity measure of a fixture is calculated as follows:where s is the similarity measure of current fixture, n is the number of theindex feature,i

43、s the weight of each feature,is the similaritymeasure of the attributeof the i2th feature with the attributeof relativefeature of the j-th case in the case library. at the same time,the value counts as follows:15精品 料推荐.whereis the value of the index attribute of the i-th feature, andis thevalue of a

44、ttribute of the relative i-th feature of the j-th case in case library.so there are two methods to select the analogical fixture. one is to set the value.if the values of similarity measure of current cases were less than a given value, those cases would not be selected as analogical cases. when the

45、 case library is initially set up, and there are only a few cases, the value can be set smaller. if there are lots of analogical cases, the value should get larger. the other is just to set the number of the analogical cases (such as10), which is the largest value of similarity measure from the sort

46、ed order.3 case adaptation and case storage3.1 case adaptationthe modification of the analogical case in the fixture design includes the following three cases:1) the substitution of components and the component;2) adjusting the dimension of components and the component while the form16精品 料推荐remains;

47、3) the redesign of the model.if the components and component of the fixture are common objects, they can be edited, substituted and deleted with tools, which have been designed.3.2 case storagebefore saving a new fixture case in the case library, the designer must consider whether the saving is valu

48、able. if the case does not increase the knowledge of the system, it is not necessary to store it in the case library. if it is valuable, then the designer must analyze it before saving it to see whether the case is stored as a prototype case or as reference case. a prototype case is a representation

49、 that can describe the main features of a case family. a case family consists of those cases whose index codes have the same first 13 digits and different last three digits in thecase library. the last three digits of a prototype case are always“ 000”. a reference case belongs to the same family as

50、the prototype case and is distinguished by the different last three digits.from the concept that has been explained, the following strategies are adopted:1) if a new case matches any existing case family, it has the same first 13 digits as an existing prototype case, so the case is not saved because it is represented well by the prototype case. or is j