【作者】 安培文；

【导师】 黄茂林；

【作者基本信息】 重庆大学 ， 机械设计及理论， 2003， 博士

【摘要】 平面连杆机构是工程实际中应用非常广泛的机构类型；同时，平面连杆机构又可视为其它基本机构的理论结构原形，是机构学理论与方法的研究中最基本、最主要的研究对象。因而，平面连杆机构始终受到学术界和工程界的高度重视。但是，平面连杆机构中广泛存在的过约束，造成机构对制造、安装误差特别是运动副元素的形位误差十分敏感；同时，由于不可避免的内部和外部不确定因素的影响，常常会造成机构运动的“障碍”及系统中某些构件的变形和运动副中的附加动载荷，引起机械的振动、冲击、噪声等而导致机械的效率和工作性能的降低。因此，寻求新的、性能良好的、具有自调与自适应性的新型连杆机构，并在新的应用中不断完善与创新，使其能够高效率、高稳定的可靠工作并具有较低的生产成本，以满足现代科学技术发展和市场竞争的需要，乃是当前所共同关注的问题。这些问题的解决有着重要的理论意义和工程应用价值。 因此，本文以平面连杆机构为研究对象，以高效、高稳定性及低成本为主要目标，对机械中的约束与过约束、自调机理与自调结构、运动副误差对平面连杆机构约束不确定性的影响程度以及无过约束机构的设计理论与方法进行了深入、系统的研究。论文的主要研究成果及创新点有以下几部分： (1) 基于广义约束的概念，从有利于设计和控制约束的原则，对机构及机械系统中的常见约束进行了分类，首次提出了“基本约束”、“静定约束”及“超静定约束”的概念和分类定义；并首次将虚约束、重复约束、消极约束、多余约束、过约束等概念，从本质上统一起来进行定义，将其都统一称为“过约束”。明确指出：过约束是人们为满足除基本自由度需要以外的其它特殊功能和结构上的需要，而人为加在机构中的、理论上不影响机构基本自由度的过多的约束。从而，为采取消除过约束对不同误差敏感的措施指明了方向，更具有工程设计的实用性。 (2) 根据过约束产生的依据不同，将封闭运动链中过约束分为“理论平面过约束”和“空间-平面过约束”两大类。首次提出了存在理论平面过约束的机构的过约束分析方法，得到了这类机构中存在的过约束的类型和数量；同时，提出其过约束消除措施和方法，得到了这类机构的无过约束自调结构。 (3) 详细分析了无过约束机构能够实现自调的机理及机构能够实现自调的条件，首次提出了无过约束机构自调性分析的一种精确方法，得到机构自调时圆柱副中的自调位移规律和机构能够实现自调的运动副允许误差角以及三种常用平面四杆机构的自调结构的最适宜的运动副配置方式。本文对机构自调特性分析的结果表明，在不同的运动副配置位置及运动副存在不同的误差情况下，误差对机构重庆大学博士学位论文自调性能的影响程度(也即机构对误差的敏感度)是不同的。其中，曲柄销轴线的误差对机构自调性能影响较大。 (4)首次提出了运动副误差对平面连杆机构约束不确定性影响度的评判指标和单因素定量分析方法，得到了机构中不同运动副的不同平面内的误差对机构性能的影响程度。本文的分析计算结果表明，平面连杆机构中的非平面约束所造成的连杆强制变形中既有扭转变形又有弯曲变形。在机构的某几个位置上有的主要是扭转变形，有的主要是弯曲变形，而一般情况下是两种变形的复合，且这种强制变形是周期性的，因而必然会引起系统的弹性振动及运动副反力的周期性变化;同时，通过算例进一步得出:机构中轴和销的轴线误差尤其是曲柄销(轴)轴线的误差对机构性能的影响是较大的，是引起机构及机械系统振动、噪声等有害影响的主要根源。此外，从整转副与摆转副的误差影响度分析结果可见，整转副误差所引起的封闭障碍及变形显然要大些。 (5)创造性的应用和发展了Assur机构结构组成原理，提出了按零过约束自调基本组进行无过约束机构设计的结构学原理与方法。并在总结自调机构中运动副配置方式的合理选用原则的基础上，对平面11级基本杆组和部分常用的平面111级基本杆组的零过约束自调基本组进行了详细的分析研究，首次得到了其对应的零过约束自调基本组。从而，为方便、快捷地设计无过约束自调机构提供了理论依据。 (6)对新型脉动无级变速器主传动机构进行过约束分析的基础上，对该系统进行了消除或减小过约束及其影响的自调结构的创新设计。对样机的传动效率及速度波动的测试结果表明本文的设计方法是正确的、有效的。 本文所做的工作，丰富了机构结构设计理论，推进了平面约束不确定影响的分析及消除其不利影响的自调机构的结构分析、设计理论与方法的研究，以及自调机构系统的工程应用，具有普遍的指导意义和重要的应用价值。更多还原

【Abstract】 Planar linkage mechanisms are used very widely in engineering and can also be regarded as the theoretical structure model of all other basic mechanisms, thus they have been gained attention by domestic and overseas researchers and engineers all the time. Nevertheless, the widely existed overconstraints in the mechanisms will make the quality of the mechanisms very sensitive to the inevitable manufacturing, assembly errors (especially, the errors resulted from the shape and position between kinematic pair elements and their axes). At the same time, because the internal and external uncertain factors such as non-plane characteristic of dynamic parameters of links (such as mass distribution, inertia forces, etc.), bending and twist of links, and the changes of environment and operating condition are inevitable, they will form the disturbance to planar constraints and make them possess the characteristic of "uncertain". The uncertainty of planar constraints causes overconstraints, which have no influences in theory on smooth work of a machine with planar linkages, to form obstruction in fact and bring about a series of pernicious influences on the performance of the machines, especially on their dynamic behavior and the quality.In order to make the mechanisms possess high efficiency, high stability, and low cost, a thorough study for constraints and overconstraints in the linkage mechanisms, self-adjusting mechanism and self-adjusting structures of the mechanisms, the degree of the influences of errors in different kinematic pairs on performance of the mechanisms, and the theory and method of designing for the mechanisms without overconsstaint was carried out in this dissertation.On the basis of the generalized constraints and on principle of designing and controlling the constraints advantageously, the conceptions such as basic constraint, statically constraint, and over-statically constraint were put forward for the first time. With this understanding, the common constraints in mechanisms and mechanical systems were classified. The uniform definition of the overconstraints was presented. According to the differences of mechanism of forming overconstraints, the overconstraints in closed chain mechanisms were divided into theoretical-plane overconstraint and special-plane overconstraint. A method, which is used to analyze for overconstraints of mechanisms with theoretical-plane overconstraint and to eliminate the overconstraints in the mechanisms, was proposed for the first time. Thecharacteristics and number of overconstraints in these mechanisms, and the self-adjusting mechanisms without overconstraint were gained.The mechanisms and conditions for the mechanisms to adjust itself were analyzed in detail. An accurate method of analyzing for the properties of the mechanisms without overconstraints was given for the first time, we obtained the equations of self-adjusting displacement in the cylindrical pair, the allowable kinematic-pair-axis errors which enable the mechanisms realize function of self-adjustment, and the most rational arrangements of kinematic pairs for the three common four-bar mechanisms. The results of analysis show that the influences of the errors of crank-pin on the self-adjusting properties of the mechanisms are bigger than that of the other pairs.A method of describing and analyzing for the degree of influences (DOI) of the kinematic-pair-axis errors on the performance of a mechanism was presented for the first time, and results of DOI of the different errors from the different kinematic pairs were obtained. The results of analysis show that: 1) DOI of the pin-axis errors, especially the crank-pin-axis errors, is bigger than other axis errors; 2) From the calculating results of DOI of the errors of the different kinematic pairs, DOI of rotate-completely pairs is bigger than that of oscillate pairs; 3) The forced coupler-deformations resulted from the constraints out of motion plane consist of twisting and bending deformation, and the deformations are variat更多还原