外文翻译-连接机械装置的缺点和纠正解决方案

1、外文翻译-连接机械装置的缺点和纠正解决方案 河南理工大学本科毕业设计(论文)外文资料翻译 题目:Defects in link mechanisms and solution rectification 连接机械装置的缺点和纠正解决方案学院: 机械与动力工程学院专业: 机械设计制造及其自动化 班级: 机制专升本05-1 姓名: 陈 志 明 学号: 0503050112 指导老师:焦 锋 连接机械装置的缺点和纠正解决方案1、绪论 从Grashof为四杆机构的识别和分类给出规那么以及Burmester提出中心点和圆点曲线开始,连杆机构的缺陷就成为一些研究的主题。即便在1883和1960之间发表过很

2、少一局部成果,一直到1967年Filemon提出了一个图解设计方法来除去缺陷的时候,在这方面才出现这个突破性的成就。从那时以后每年都会有许多有关缺陷的论文发表。六十年代约25篇,在七十年代大约41篇, 在八十年代大约54篇然而在九十年代只有40篇论文。如此40年来这个专业研究已经在全世界展开,涉及研究人员超过70个,以论文形式,M.S. 和Ph.D.的论题,论文,专利,公告和其他发布形式,记录超过170项,它们以图解、数字和计算等方法研究这些问题。这个课题的持续稳定的开展说明了它在机构综合领域的重要性。Filemon是第一个讨论缺陷的人。Waldron,Barker,Gupta 等人是主要的奉

3、献者。 Chase和Mirth精确的区分了回路和支路,这是有记录的缺陷研究方面的重要成果。 在使用 Burmester 曲线进行综合的时候, 发现一些解理论上完全能满足规定的几何条件,但是不能满足真实的装配条件。原因是这些机构虽然在规定的4个位置是可安装的,但:1 不能够在四个规定的位置之间连续地运动或2 运动是连续的,但是位置的次序是错误的或3 它们在从一个位置运动到另一个位置时需要拆开才能完成在不拆开重新装配的情况下不能完成这一运动或4它们变换运动的方向。 出现这样一些情况的原因是机构中存在一种或较多的类型的缺陷,这些在综合时没有考虑到。对机构中这类缺陷的研究在40多年来已经引起许多研究者

4、的注意而且它正在继续吸引他们。 在这一篇论文中,把关于这个课题的能得到的文献进行了回忆。 它在尝试追寻该领域的历史,突出其主要开展趋势并讨论重大的奉献。 文中列出的参考文献所涉及到的大都为平面连杆机构,还一定程度涉及了的空间球面机构。 它是具有相当的代表性,能被广泛理解的,但并不完整。2. 机构中缺陷的类型机械机构的缺陷可以被分为: Grashof (曲柄)缺陷 顺序缺陷 回路缺陷 分支缺陷(变换点或死点位置缺陷) 差的传动角。 回路,支路,顺序, Grashof机构 和非Grashof 机构和传动角等知识对成功综合一个可行机构是根本的知识。 它对机构分析也是有用的。 许多动力学家对设计中传动

5、角标准方面作了详细的工作。在66这本书中对和传动角有关的工作作了一个大体回忆 。 因此,这一论文只限于介绍前四类缺陷。 方案校正意味着(如果有的话)从方案中消除任一缺陷,以下几点要求方案校正:?为获得一个完全没有缺陷的机构。多重缺陷校正的连杆机构可以通过把Burmester曲线分成多段,使每段都没有各种缺陷来获得。?减少机构的解空间这样可以减少得到一个可行的设计的迭代次数。 如此就减少了综合所需的时间。?在某一些情况下是没有满足条件的方案,所以应该放弃进一步的尝试和防止寻找解决方案的不必要的时间浪费。?减少功率损失和增加力与运动传输的效率。?将过程编入电脑程序以减少计算时间。对一个可调四杆机构

6、,使其一个或两个参数可自由选择能够得到比没有自由选择参数更好的结果。这是因为连杆设计不仅要满足根本的方程,同时它还要满足如分支、顺序问题、传动角和效率等要求。4. Grashof 校正 众所周知,不可能所有的连杆机构都具有能转整周的曲柄。人们常常渴望有这样一个曲柄因为连杆机构可以被一个连续不断的旋转电机驱动。因此在任何综合过程中,区分开拥有整转曲柄的方案是非常重要的。这个问题被称为Grashof问题,因为Grashof准那么被用来区分机构是否具有旋转的曲柄。4.1 Grashof 准那么(I) 如果l是最长的连杆,s是最短的连杆,p和q是剩下的平面四杆机构的另外两杆如果 l+sp+q 那么机构

7、仅有一个整转的曲柄。(II)最短的杆件必须是曲柄或机架。如果是曲柄,那么机构是一个最短连杆为整转曲柄的曲柄摇杆机构。如果最短杆为机架,这个机构是一个输出和输入构件都转整周的双曲柄机构。基于Groshof准那么,机构称为: Grashof 机构 最短杆是整转的曲柄或机架 非Grashof 机构机构中没有整转构件。4.2 Grashof (曲柄)缺陷 如果在机构中的没有可能转整周的构件,那么机构称为具有 Grashof 缺陷的机构。当最短的连杆既不是一个主动件也不是机架构件的时候 , 会有这种缺陷。举例来说;所有的三摇杆机构除了机架之外全是摇杆。4.3 Grashof 校正 Grashof 校正意

8、味着Grashof缺陷的除去或选择只有那些满足Grashof准那么的连杆机构。除去Burmester曲线上没有Grashof机构局部和识别出曲线上的满足Grashof的不等式准那么的一局部,就可以消除缺陷。为了决定弧线段的Grashof的类型,在圆点曲线上找到连杆机构的最短杆是非常必要的。 4.4 Grashof 校正的文献回忆 Grashof给出了一组准那么来把四杆机构识别并分类为双曲柄、摇杆曲柄和双摇杆机构。Hain,Beggs和Hartenberg没有证明地提到了这些,然而 Blaschke和Muller,Harding和Midha给出了不完全的证明。Filemon和Paul确定了区别两

9、种双摇杆机构的方法。也就是,区分那些有完全回转的连杆和那些摆动的连杆。 他们依以下各项重新表达了 Grashof准那么:1 有两种不同类型的双摇杆机构,因此连杆机构共有四种根本类型。 2Grashof's 的不等式的满足对至今存在一个回转的曲柄是一个充分必要条件。 3Grshof判据的等式形式是机构存在变换点的一个必要充分条件。 Gupta藉由检测传动角的极值直接发现了相同的等式条件。Kohli和Khonji由分析得到了球面五杆机构组的可转性判据。他们对一个球面的五杆机构推导出了个别输入可转性条件及全部可转性条件。 Ting和Tsai为五杆杆组提供了一个有效简单的 Grashof型可动

10、性判据而且把他们分类为(i)双曲柄机构和ii非双曲柄机构。对这二种类型的工作区域也进行了研究。 Ting提出了五杆机构的Grashof准那么并证明了与四杆机构Grashof准那么是相同的。他也把它们分类为:i、一级五杆机构: a双曲柄或三曲柄,b一个有条件的双曲柄或单曲柄机构组,c零曲柄机构和 ii 二级五杆机构-非双或非三曲柄机构,a有条件的双曲柄机构;b单曲柄机构; c与输入和固定构件条件有关的零曲柄机构。 Tting提出了N杆 N连杆数活动性准那么,用来控制装配性和旋转性i以决定任何的单一闭环N杆运动链的整转性,ii 预知在任何二个毗连的构件间的可转性,iii 说明而且识别特殊位形的存在

11、 ,iv 分类连杆机构v 说明在不同的等级连杆机构之间的特殊位形的差异或识别他们的之间不能旋转角的差异。Barker给平面四杆机构一个完全和系统的分类由 Grashof,非 Grashof和变换点类型所组成。其重要的特性作为解空间的特征外表给出。这些可能被用来创立设计线图,这些线图可用来选择具有期望特性的机构。 Barker和Shu提出了一个方法,那个方法中三个设计位置方程序与无量纲构件长度的相等偏差状条件相结合,得到一个三次多项式。这个多项式的根产生可能的解决方案,它们必须进行评估。在缺陷被消除后,剩余的方案产生无缺陷的 Grashof-曲柄-摇杆- 摇杆和 Grashof- 曲柄- 曲柄-

12、 曲柄机构,这些机构在传动角上相等偏差。 Zhao 等人用数值的方式对平面机构的可动性区域进行了研究。 Williams和Reinholtz给予了Grashof准那么的证明;使用多项式的 s 定律区别。Angeles和Callejas提出了Grashof可动性准那么的一个代数公式;并采用梯度法对平面连杆机构进行优化。 Norton等人 给出了三角形不等式概念用来证明如果可动性角给定,那么存在机架的铰链点位置解空间的两个不同区域,即 Grashofian 和非Grashofian区域。Kimbrell 和Hunt讨论Grashof和Non-Grashof四杆结构的渐近位形。 Rastegar对空

13、间机构的可动条件引出提出了一个一般的方法,包括传动角限制。 没有这些限制,这些条件必须对机构的每一对相似的位形分别导出。Rastegar提出几何学的近似值技术过去在缺少传动角限制一直为获得空间RSSR机构的闭环Grashof- 型可动性条件。Sen 和 Mruthyunjaya 以为机构应该最好有限制的可转性。整转性不但减少奇异而且给工作空间较好的运转精度。如果机构不能整转, 首先,他们建议丢弃在模拟试验期间产生没有完整的旋转的所有机构。如果机构部份地是旋转的, 全部接受 局部旋转机构直到获得一个整转机构。 Gupta等人进行了平面和空间机构的可动性分析,通过机械手手腕设计应用对球面的四杆机构

14、可转性准那么进行了灵活性分析。 Angeles和Bernier对平面四杆机构也做了一样的工作。 Waldron确定出具有整转曲柄的Burmester综合方案而且讨论了消除掉不需要的 Grashof 位形。Davitasvili设计了五杆铰链机构。Ting用证据证明N- 杆可动性定律。Fox和Willmert通过不等式考虑了角驱动结束优化了曲线生成机构的设计。 Alizade 和 Sandor 确定了空间四杆机构的完全转动曲柄的存在条件。 Nolle研究了 RSSR 机构运动的范围传递转移。 Skreiner 识别了空间四杆机构的可动性区域。 Pamidi 和 Freudenstein 讨论了五

15、杆 RCRCR 空间机构的运动。 Freudenstein 和 Primirose对变形四杆机构提出了曲柄的标准。Harrisberger 作了空间四杆机构的活动型分析,Sticher用椭圆线图法对RSSR机构作了同样的结构分析。Savage和 Soni 对所有的球面四杆机构作了独特的描述。 Paul给出了约束度的统一标准。 Duffy 和 Gilmartin 给出了具有不同运动列的空间四杆机构的位置限制。 他们也继续对球面四杆机构的可动性作了分析。 Jenkin等人研究了空间机构的总体运动。 Khonji 讨论了球面的五杆机构的可转性准那么。4.5 Grashof类型和回路的关系 Svobo

16、da做了Grashof类型校正同时包括回路校正, Filemon , Waldron ,Barker, Jeng ,Chase和Mirth讨论了同样的问题。 Grashof 型四杆机构非变换点机构,有二个回路。非Grashof四杆只有一个回路。因此任何的非 Grashof解方案保证无回路缺陷。当且仅当测试角 改变在精确位置之间时 , Grashof 四杆机构变更回路。测试角是两个内角之一,在连杆机构最短边的对面,在每一个精确位置都要测试。它是从最短边的对边到最短边的相邻边逆时针测量,在范围内。 Defects in link mechanisms and solution rectificat

17、ion1.Introduction Since from Grashof set the rules for indentifying and classifying the four-bar mechanisms and Burmese presented the center point and circle point curves, the defects in the mechanisms have been the subject of several studies. Even though a very few works are published between 1883

18、and 1960, the break through took place when Filemon proposed a graphical construction to eliminate the defects in 1967 Since then no year went without the publication of a paper on defects. In sixties about 25, in seventies about41, in eighties about54 whereas in nineties as good as 40 works were re

19、ported. Thus the major study has been stretched over 40 years by more than 70 researchers all over the world and recorded in the form of papers, M.S. and Ph.D. theses, reports, patents, bulletins and other publications numbering more than 170 in all graphical, numerical and computational methods. Th

20、e constant growth of the subject shows its importance in the field of syntheses. Filemon appears to be the first person to address many of the defects. Waldron et al., Barker et al., and Gupta et al. are the major contributors. Chase and Mirth distinguished circuit precisely from branch placing the

21、critical study of the defects on records When using the Burmester curves for synthesis, it is discovered that some of the solutions fulfill the prescribed geometrical conditions theoretically but the constructional reality is not met with the cause for this is that these mechanisms-altough mountable

22、 in the four prescribed positions:1 Are not able to move continuously between the four prescribed positions or2 The movement is continuous but the order of positions is wrong or3 They need to be disconnected while moving from one position to the other cannot move without disconnecting and reassembli

23、ng or4 Change the direction of motion The reasons for such situations are the presence of one or more types of the defects in the mechanisms that are not taken care of while synthesizing the mechanisms. Study of such defects in the mechanisms has drawn the attention of many researchers for over four

24、 decades and still it is continuing to attract them In this paper, a review of the literature available on the subject is made. An attempt is made to trace out the history highlighting major trends and discussing significant contributions. The references listed concerned largely to planar link mecha

25、nisms and to some extent spatial spherical mechanisms also. It is fairly representative and comprehensive rather than being complete.2. Types of defects in the mechanism The defects in the mechanisms may be identified as:Grashofs crank defect,order defect,circuit defect,branch defect change point or

26、 dead center position defect,poor transmission angle The knowledge of circuit, branch, order, Grashof and non-Grashof linkages and transmission angle is essential for successful synthesis of a feasible mechanism. It is also useful for analyzing the mechanism. Many kinematicians in detail have dealt

27、with the work on the transmission angle criteria of design. A broad review of works pertaining to the transmission angle is found in. Hence, this paper constrains to the first four types of defects only.3.Need for the solution rectification Solution rectification means the elimination of defects if

28、any from the solution The need for the solution rectification arises also from the following requirements:To get a mechanism completely free from defects. Linkages rectified for multiple defects are obtainable by intersecting the Burmester curve segments free of each defect individually To reduce so

29、lution space of mechanism that tends to reduce the iterations to arrive at a feasible design. Thus to reduce the time required for the synthesis To show that in some cases there are no solutions, which fulfill the conditions so as to give up further trial and to avoid the unnecessary waste of time i

30、n the course of finding the solution To reduce power losses and increase the efficiency of force/motion transmission To make the procedure codable into a computer program and to reduce the computing timeUsually one gets better results by having one or two free choices of parameters for an adjustable

31、 four-bar linkage, than solution without any free choice of parameter. This is because the design of linkage has to satisfy not only the basic equations but also the conditions like branch and order problem. Transmission angle and efficiency.4. Grashof rectificationIt is a known fact that all the li

32、nkages may not posses fully rotatable crank. It is usually desirable to have such a crank so that the linkage can be driven by a continuously rotating motor Therefore in any synthesis procedure it is important to be able to separate solutions, which do possess fully rotating cranks. This problem has

33、 been referred as the “Grashof problem because Grashofs rules areeused to distinguish linkages with fully rotating cranks.4.1. The Grashofs rule ? If l is the length of the longest link, s is the length of the shortest link and p and q are the lengths of the remaining two sides of a planar four-bar

34、mechanism, the linkage can only have a fully rotatable crank if, l + s p + q ? The shortest link must either be a crank or the base. If it is a crank, the linkage is a crank-rocker with the shortest link as fully rotatable crank. If the shortest link is the base, the linkage is a drag link with both

35、 in put and out put links fully rotatable. Based on the rules the mechanisms are named as follows:Grashofs MechanismLinkages in which the shortest link is fully rotatable or the base fixed link Non-Grashofs Mechanism Linkages in which no link is fully rotatable.4.2. Grashof;s crank defect If no link

36、 in the mechanism is capable of rotating fully, the linkage is said to have Grashof defect. This happens when the shortest link is neither a driving link nor a ground link. For example; the triple rocker mechanism in which all the links except the ground links except the ground link are the rockers.

37、4.3. Grashof rectification Grashof rectification means the elimination of Grashof defect or selecting only those linkages , that satisfy the Grashof rule. Deleting the portions of the Burmester curves, which do not give the Grashof mechanism and identifying the segments of curve on which the Grasof

38、inequality is satisfied can de this It is necessary only to locate the shortest link of the linkage given by any circle point on that segment in order to determine the Grashof type everywhere on the segment.4.4. Review of literature on Grashof rectification Grashof gave a set of rules to identify an

39、d classify the four-bar mechanisms into double cranks, rocker cranks and double rockers. Hain, Beyer, Begs and Hartenberg referred these without proof whereas Blaschke and Muller, Harding and Midha et al. published incomplete proofs. Filemon and Paul identified the lacuna to distinguish between the

40、two types of double rockers, i.e., those with fully revolving couplers and those with oscillating couplers. They restated the Grashofs rules as follows; 1 There are tow distinct types of double rockers and therefore four basic types of four-bar linkages. 2 Satisfaction of Grashofs inequality is a su

41、fficient as well as necessary condition for existence of minimum of one revolving crank. 3 Equality form of Grashofs criterion is a necessary and sufficient condition for the existence of change point mechanism Gupta found the same equality conditions more directly by examining the extreme values of

42、 the transmission angle. Kohli and Khonji derived rotatability criteria of spherical five-bar linkages analytically. They developed the conditions of individual input revolvability and the conditions of full rotatability for a spherical five-bar linkage. Ting and Tsai presented an effective and simp

43、le Grashofs type mobility criterion for five-bar linkages and classified them into i double-crank linkages and ii non-double-crank linkages. The working area of two types is also investigated. Ting proposed five-bar Grashofs criterion and proved the same through the use of four-bar Grashofs criterio

44、n. He also classified them into i Class-I five-bar mechanisms: a double crank or triple crank, b a conditional double- or single-crank linkage, c a zero-crank linkage and ii Class-II five-bar mechanisms-non-double-or non-triple-crand linkage;a double crank or triple crand, b single-crank linkage, c

45、a zero-crank linkage depending on the condition of the input and fixed links Ting proposed N-bar N number of links mobility criteria which govern the assemblability and rotatability i to determine the full rotatability of any single-closed-loop N-bar chains,ii to predict the revolvability between an

46、y two adjacent links,iii to explain and identify the existence of singular positions ,iv to classify the linkages and v to explain the difference of singular positions between the linkages of different classes or to identify the difference between their non-revolvable angles Barker gave a complete a

47、nd systematic classification of planar four-bar linkages consisting of Grashofs, non-Grashofs and change point types. The significant properties are presented as characteristic surfaces within the solution space. These can be used to construct design charts permitting the selection of mechanisms wit

48、h desirable properties. Barker and Shu presented a method in which three design position equations are combined with equal deviation condition on the non-dimensional link lengths to produce a third-order polynomial. The roots of this polynomial produce potential solutions, which must be evaluated fo

49、r defets. After the defects are removed, the remaining solutions yield defect-free Grashof-Crand-Rocker-Rocker and Grashof-Crank-Crank-Crank mechanisms, which have equal deviation on the transmission angle. Zhao et al., dealt with mobility region of planar linkage by numerical approach Williams and

50、Reinholtz gave the proof of Grashof;s law using polynomial discriminates.Angeles andCallejas presented an algebraic formulation of Grashof;s mobility criteris with application to planar linkage optimization using gradient-dependent methods. Norton et al. gave the triangle inequality concept used to

51、prove that if the mobility angle is given, two distinct regions of base pivot locations solution space exist, the Grashofian and no-Grashofian region. Kimbrell and Hunt discuss the asymptotic configurations of Grashof and non-Grashof four-bar linkages Rastegar presented a general method for the deri

52、vation of movability conditions for spatial mechanisms that may include transmission angle limitations. In the absence of these limitations, such conditions must be derived separately for each pair of similar configurations of the mechanism. Rastegar presented a geometrical approximation technique u

53、sed to derive closed-form Grashof-type movability conditions for spatial RSSR mechanisms in presence and absence of transmission angle limitations Sen and Mruthyunjaya opine that the mechanism should preferably have finite rotatability. Complete rotatability not only reduces the singularities but also gives workspace of better accuracy of performance. If the mechanism is not fully rotatable, to start with, they suggest