基于虚拟运动中心概念的机构设计理论与方法

1、附件 2论文中英文摘要格式作者姓名： 裴旭论文题目 ：基于虚拟运动中心概念的机构设计理论与方法作者简介：裴旭，男， 1979年 10月出生， 2004年 9月师从于北京航空航天 大学宗光华教授、于靖军副教授（副导师） ，于 2009年 7月获博士学位。中文摘要现代机械装备或产品正向“重大精尖”和“微小精密”方向迅猛发展，对作为其骨架与 执行器的机构（包括少自由度功能机构、柔性机构等）提出了更高、更为特殊的功能要求。 建立基于超精密运动的创新设计理论与方法已成为当前机构学研究的一个重要主题。鉴于对 精度、控制等产生消极影响的寄生运动在多数机构中普遍存在，而在拓扑层面上就能采取减 小或抑制寄生运动

2、的措施，往往能起到事半功倍之效。在微创外科领域应用甚广的虚拟运动 中心（ VCM ）机构即可实现类似的功效，其功能也被业界广泛认同。同时，在装备制造业、 航空航天等工业领域的应用也大有潜力可挖。以加工刀头 Z3 为例，由于主体采用的是传统 3-PRS 构型，寄生运动的影响比较明显，如果从 VCM 型综合的角度加以优化，可在性能方 面得到显著改善。而柔性 VCM 机构则提供了一种综合新型高精度大行程柔性铰链（机构） 的可能性。论文在多项国家自然科学基金的资助下， 以一类特殊的少自由度功能型机构 VCM 机 构为研究对象，对其构型综合与设计方法进行了系统深入的研究，并通过将 VCM 概念和柔 性机

3、构有机结合，建立了一套行之有效的大行程高精度柔性铰链（及柔性机构）分析、设计 方法和理论。论文的主要研究工作和创新性成果如下：1. 基于对当前刚柔两类并联机构构型综合方法研究的现状分析，指出了可统一实现刚柔并 联机构构型综合的可行性。以旋量理论为数学工具，结合模块化思想理念，提出了一种 可以实现刚柔机构统一构型综合的普适性方法。该方法的核心在于建立几何模块、运动 （约束）模块与机械模块三者之间的映射关系，优点在于简单、可视化。基于所提出的 模块分层映射方法，通过实例初步验证了该方法对刚、柔两类并联机构构型综合的有效 性，为系统构筑可视化的刚柔并联机构统一构型综合的算法及软件提供了理论支撑。基

4、于所提方法实现了对刚性 1R, 2R, 3R-VCM 机构，以及柔性 1R-VCM 模块的构型综合， 并 且得到了多种新型的 VCM 机构。此外，还提出了一种新颖的基于几何空间映射的柔性VCM 模块的构型综合方法，优点在于可以从一种简单的直线运动模块出发，构造出多种 新型的柔性 VCM 铰链。2. 针对传统伪刚体模型法在大行程簧片式柔性铰链的建模效率和精度上存在的不足，提出 了一种新的基于 VCM 概念的伪刚体建模方法。 可方便地确定伪刚体模型的铰链位置以及 所加扭矩弹簧的刚度。这种参数化的伪刚体模型在柔性铰链的设计或优化阶段非常有用， 其主要建立在以下两个假设上：a.柔性铰链的转动中心相对固

5、定。b伪刚体模型在一定变形范围内，其铰链位置和弹 簧刚度等参数变化较小，且变化是连续的。通过对几种典型的大变形柔性铰链（如平行四杆型柔性机构、 LITFP 、交叉簧片型柔性铰 链、车轮型柔性铰链以及蝶形柔性铰链）的刚度、精度和最大行程特性进行理论分析、 仿真与实验验证， 结果表明通过所提方法建立的伪刚体模型在铰链较大变形 （50°60°内） 时仍能保持较高精度（误差不超过 10%），在较小变形时更加准确（误差不超过 1%）。3. 研究中发现： 由于柔性 VCM 铰链由于其转动中心不在铰链上， 使其比普通柔性铰链更容 易叠加，从而方便构造行程更大的柔性铰链。基于此设计思想，提

6、出了基于柔性单元组合的大行程柔性铰链设计方法。以等腰梯形柔性铰链（LITFP ）为例验证了该方法的有效 性，并得到了多种新颖的性能更优的 D-LITFP （两个LITFP组合）和Q-LITFP铰链（四 个 LITFP 组合）。通过组合，柔性铰链的最大行程成倍增加，刚度减小，但精度特性却和 组合的方式相关。经过特定的组合，多个柔性铰链的轴漂会相互抵消，从而使设计出的 柔性铰链精度更高。如得到的一种新的非对称形式的 D-LITFP 可取代传统的车轮型柔性 铰链。在最大行程、刚度相同的情况下，这种 D-LITFP 可得到比车轮型柔性铰链高得多 的精度。基于所提方法，还设计了包括大行程虎克铰、柔性滑轨

7、、柔性仿生腰等在内的 多种新构型。4. 在对大行程柔性铰链性能准确分析的基础上，提出了一种基于刚柔耦合寄生运动相互抵 消的柔性近似直线机构的设计方法。该方法主要将柔性铰链转动中产生的轴漂和其转动 时产生的偏移量进行抵消，从而实现机构上一点的直线运动。该方法的优点在于：通过 合理优化，柔性机构可以在较大的行程范围内得到很高的直线度，因此尤其适用于轴漂 较大的大行程柔性铰链设计中。由于采用了伪刚体模型，这种方法也可以方便地用于刚 性近似直线机构的设计中。最后以柔性 Roberts机构为例，对大变形柔性直线导向机构的 设计和优化方法进行了研究，得到了一些高精度大行程的柔性直线导向机构，验证了所 提方

8、法的有效性。5. 结合特殊应用背景， 对几种特殊功能的 VCM 机构进行了具体设计与分析实验。 如针对微 创手术应用的双平行四杆型及绳驱动 RCM 机构的设计、用于人机界面的重力平衡 VCM 机构的设计、基于 VCM 原理的轮式移动越障机器人的设计等。 提出了对杆件弯折的双平 行四杆型 VCM 机构的 3重物重力平衡的方法， 并加工样机对这种方案进行了验证。 此外， 设计并加工了其他一些新型 VCM 机构，如钢丝绳驱动的 VCM 机构、基于仿图仪的 VCM 机构、可调 VCM 机构。特别是将 VCM 概念用于轮式移动机器人中，对自适应机构进 行改进和设计可以有效地提升其越障性能。总之，论文研究

9、内容既涉及了刚、柔两类 VCM 机构的构型综合、分析建模以及设计方 法，也有针对性地对几种新型的 VCM 机构进行了具体设计与应用示范。这一工作将为扩展 VCM 机构在精密工程、医疗、生物工程、 工业自动化等领域的应用提供强有力的理论和技术 支持。论文在刚、柔 VCM 机构的构型综合、 基于 VCM 概念的大行程柔性铰链建模与性能评价、 大行程柔性铰链及柔性直线机构设计方法、以及面向特殊应用背景的 VCM 机构设计等方面 均取得了创新性的研究成果，围绕这几方面的创新点，以第一作者或第二作者（通讯作者或 者导师为第一作者）共发表论文 15 篇（在 Journal of Mechanical De

10、sign/Journal of Mechanism and Robotics 上发表 3 篇，在 Mechanism and Machine Theory 上发表 2 篇，在 Precision Engineering上发表1 篇）,被SCI收录5篇，El收录12篇次。总共获得6项中国发明专利授 权。以论文内容为主，作为主要完成人完成了国家自然科学基金 5 项（课题负责人为第一完 成人）。以该论文的延伸内容为主，作为负责人所申请的项目获得了国家自然科学基金、中国 博士后基金特别资助等项目的资助。关键词： VCM 机构， RCM 机构，柔性铰链，型综合，精度，旋量理论， 模块，直线机构Desig

11、n Theories and Methods of Mechanisms Based on Virtual Centerof Motion ConceptPei XuABSTRACTWith the rapid development of modern mechanical devices orienting at micro-nano scale and super-precision accuracy, some special requirements for designing key components, i.e. mechanisms, have been brought fo

12、rward correspondingly. These special mechanisms include lower-mobility functional mechanisms, compliant mechanisms, etc. Establishing some design theories and methods relating to these mechanisms is becoming a very hot issue in the field of mechanisms and robotics research. In view of parasitic moti

13、on commonly exists in a large number of current mechanisms, which may lead to a passive effect on their accuracy and control. Therefore, an effective solution is to decreaseor conterpart this parasitic motion at the level of structure topology. A VCM (Virtual-center-of-motion) or RCM (Remote-center-

14、of-motion) mechanism, widely used in the micro invasive surgery, is such a kind of device which can achieve similar effect. Moreover, this kind of mechanism have a large application potential on precision manufacturing and aerospace fields. Take a machine tool called Z3 as example, it is a 3-PRS par

15、allel mechanism with some parasitic motion. If some new VCM mechanism configurations is employed, the accuracy performance can be improved greatly. Whilst a compliant VCM mechanism just provides a possibility of high-precision and large-stroke flexures and flexure mechanisms.Granted by the National

16、Natural Science Foundation of China, by treating minimally invasive surgery and precision enginneering as the two main application backgrounds, and positioning a VCM (Virtual-center-of-motion) mechanism as a new kind of reduced-DOF function-oriented mechanism, this paper aims at carrying out the res

17、earch on the type synthesis, design methodology and innovative design for the VCM mechanism. What is more important, by combining compliant mechanisms with the VCM conception, an analysis and design methodology for large-deformation and high-accuracy flexural pivots and compliant mechanisms is propo

18、sed in terms of its equivalent rigid-body model established in this paper. The main work and innovative contributions of this dissertation are as follows:1. Based on the state-of-art analysis for main type synthesis approaches related to rigid and compliant parallel mechanism, respectively, it is pr

19、oven to be feasible to establish a unified methodology for type synthesis of these two classesof mechanisms.That is a type synthesis philosophy in terms of the Hierarchy mapping between mathematic, physical, and mechanical building blocks in the framework of screw system theory, as addressed in this

20、 paper. The key point of the proposed method lies in establishing the mapping among three different building blocks (i.e. geometric building block, kinematic or constraint building block, and mechanical building block). As a result, it makes the type synthesis process simple and visible. By using th

21、e proposed method, two type syn thesis examples are take n to verify the effective ness for the type synthesis of both rigid and flexure mechanisms. The content of this paper may provide a theoretical frame for con struct ing a visualized algorithm or software about the un ified type syn thesis (or

22、con ceptual desig n) of both rigid and flexure mecha ni sms. The type syn thesis of 1 3 DOF both rigid VCM and compliant VCM mechanisms is addressed systematically, and a large nu mber of no vel con figurati ons are obta ined corresp ondin gly .In additi on, an approach to the type syn thesis of com

23、plia nt VCM flexures is proposed based on in varia nt mapp ing among different geometry space. The advantageof this method is that many novel flexures can be con structed from a known complia nt straight-li ne mecha ni sm.2. Aiming at shortcoming of the pseudo-rigid-body model (PRBM) at modelling ef

24、fect and accuracy for large-deformation beam-based flexures, a new method for modeling its equivalent-rigid-body model (ERBM) based on VCM concept is proposed. By using this method, the joint position and the torsional stiffness corresponding to the ERBM can be determ ined convenien tly. This parame

25、terical ERBM is especially useful for the optimal desig n of flexures. Nevertheless, the model need to be established two assumptions: a. the rotation cen ter of the flexural pivot is fixed comparely; b. both the pivot locati on and torsi on stiff ness in the ERBM varies little and rema in within a

26、limited deformati on range with con tituously. The results of both theoretic analysis and FEA simulation (or experiment) on stiffness, accuracy and maximum deflecti on characteristics for several typical large-deformati on flexures in cludi ng the parallel linear spring stage, LITFP (Leaf-type Isosc

27、eles-trapezoidalFlexural pivot), cartwheel hin ge, cross strip pivot, and butterfly flexure pivot have verified that the equivale nt rigid model is also accurate (error less tha n 10%) eno ugh duri ng a larger deflect ion (5060°.3. Due to a virtual cen ter of rotati on in stead of real joi nt a

28、xis in a complia nt VCM flexural pivot, it is prone to combining with each other compared with a traditional flexure. Just because of its characteristics with a virtual center of motion, this kind of pivot can be easily superimposed to con struct new complex flexure joi nts. In terms of this idea, a

29、 desig n methodology for large-deformati on and high-accuracy flexural pivots is proposed based on complia nt build ing blocks and their equivale nt rigid-body models established. LITFP as an in sta nee verified the effective ness of this method. In the mean time, many no vel but high-performa nee D

30、-LITFP flexures (comb in ati on of two LITFPs) and Q-LITFP ones have bee n obta ined corresp ondin gly. In terms of comb in ati on of two and more VCM flexure modules, the resulta nt compo und flexural pivot has such good characteristics as larger stroke, and smaller rotational stiffness. Its accura

31、cy, however, is releva nt with the comb in ati on ways. In some cases, the axis-drift can be con terparted by means of specified comb in ati on, which leads to flexural pivot with higher accuracy. For instanee, an asymmetric D-LITFP may be replacement of traditional cartwheel hinge in that the forme

32、r has much higher performance than the latter in the case of the identical maxmium stroke and rotational stiffness. In addtition, in terms of combination of two and more compliant VCM mechanisms, some new large-deformation compliant universal joints and compliant translational ones have been constru

33、cted. And also a novel 3-DOF compliant waist configuration has also been obtained.4. Based on the accurate performance analysis for some typical large-deformation flexures including LITF pivot and cross-axis hinge, a simple method for design of compliant approximate straight-line mechanisms is addre

34、ssed in terms that the center-shift can just make up for the offset caused by the rotation for a particular point. Such a viewpoint in view of counteracting both the rigid and compliant parasitic motion establishes a bridge between flexure joints and compliant straight-line mechanisms, and lead to a

35、 new way to design, analyze or optimize compliant straight-line mechanisms. In addition, the main advantage of this method is that a very high-linearity straight-line motion within a large stroke can be achieved via optimization for this kind of compliant mechanism, therefore, the method is particul

36、ar useful for design of large-stroke flexure mechanisms.Since the concept of PRB is used to connect the rigid and compliant mechanism, the proposed method is also adaptable for rigid straight-line mechanisms. To illustrate and verify the proposed method, a kind of flexure joint, LITF pivot (or Rober

37、ts mechanism) is used to reconstruct several large-stroke and high-accuracy straight-line compliant mechanisms. The results are verified by FEA method, which show that the proposed method can derive a large-deflection flexure joint into approximate straight-line mechanism with a high linearity.5. Ai

38、ming at some applications such as minimally invasive surgery, some representive special-purpose RCM mechanisms such as double parallelogram RCM mechanism have been analyzied, designed and fabricated, and the static balance of double parallelogram VCM mechanisms are discussed and a counterweight bala

39、ncing method with three is addressed correspondingly to achieve the static-balance of a general double parallelogram VCM mechanism with offset linkages. An example is given to illuminate the design process. The VCM mechanism is also employed in robots which were mobile on rough terrain for its speci

40、al characteristics.All above designs and developments of mechanical models, or prototypes are addressed with the support from the theoretical modeling, FEA simulation and experiments. This work will surely provide the theoretical support both in enriching the family of VCM mechanisms and in expanding their applications in precision engineering, medical treament, bioengineering, in