【作者】 于淼；

【导师】 赵继；

【作者基本信息】 吉林大学 ， 机械制造及其自动化， 2004， 博士

【摘要】 金属切削机床发展至今，总的说来，它们的基本结构没有什么变化，一般都采用由床身、立柱、主轴箱和工作台等部件串联而成的非对称“C”型布局，这种布局使机床机构复杂，受力和热变形不均匀、误差累积加大。而虚拟轴机床(并联机床)彻底打破近两个世纪以来以笛卡尔坐标直线位移为基础的机床结构和运动学原理，将机床结构技术与机器人技术相结合，以空间并联机构(并联机器人)为基础，以软件取代部分硬件，以电气装置和电子器件取代部分机械传动，具有结构简单、传动链短、环境适应性好、技术附加值高等优点。 虚拟轴机床发展至今已有10年，世界各国已经开发研制出多种结构构型的专用机床，有的已进入实用化阶段。总的说来，虚拟轴机床具有模块化程度高，易于重构，机械结构简单，但也存在着明显的不足，即在刚度、精度以及作业空间等方面存在着明显的缺陷。因此，如何扬长避短地开辟虚拟轴机床的应用新天地，便成为该领域具有重要研究价值的战略选择。本课题组在虚拟轴混联机床的开发中，寻求和开拓其在模具曲面自动精加工中的新领域，充分利用弹性加工的特点，通过巧妙设计弹性研抛工具系统将其用于自由曲面的研抛加工中。本文所做的探索为拓展虚拟轴混联机床的应用领域开辟了新的道路。 虚拟轴混联研抛机床是一个包含多环闭链机构的复杂多体系统，与传统的串联机构相比，建立动力学方程是较为复杂而困难的。虚拟轴混联研抛机床与机器人不同，在动力学方面有许多自身的特点，特别是对于自由曲面研抛加工这样一种特殊的加工形态，其结构抗振性和加工稳定性是主要考虑的问题。因此，虚拟轴混联研抛机床的动力学分析就成为改善系统动态性能的关键。目前，建立虚拟轴混联研抛机床动力学方程均是把机床抽象成多刚体系统，应用多刚体系统动力学的建模方法，将虚拟轴混联研抛机床的各个支杆和平台看作是独立的子结构，建立各自的动力学方程，然后根据子结构之间的约束关系建立系统的约束动力学方程。由于虚拟轴混联研抛机床本身结构的特点，各部件刚度相差较大，比如支杆的刚度就弱于动、静平台，所以，在运动时支杆本身的变形便不可忽视，并且在支杆变形的同时，又与虚拟轴混联研抛机床摘要......鱼鱼鱼鱼鱼鱼鱼旦鱼旦旦旦鱼旦旦旦旦旦旦旦旦旦鱼旦旦旦旦旦鱼旦旦旦旦旦旦旦旦旦旦旦旦旦旦旦旦鱼旦坦旦旦旦，口，月旦归，，-旦鱼鱼口...鱼鱼，，..州旦旦旦鱼整体的刚性运动相互作用或祸合。 基于此，本论文将多柔体系统动力学的建模方法引入虚拟轴混联研抛机床的动力学分析中，应用L口grange方程建立了空间刚一柔祸合多体系统动力学模型，并根据3一PTT并联机构的铰接特点，建立虚拟轴混联研抛机床并联机构的空间约束方程，以及欧拉参数的附加约束方程，进而得到约束Jacobian矩阵方程。通过空间约束方程，将3一PTT并联机构各个部件组装，建立3一PTT并联机构约束多柔体总体控制动力学方程。同时结合串联机构的结构和铰接特点，将串联机构看成是多刚体系统，运用同并联机构同样的处理方法，建立了串联机构约束多刚体总体控制动力学方程。 由于多柔体系统动力学控制方程的强祸合性和高度非线性，通常得不到解析解，必须借助于数值解法。根据上述建立的多柔体动力学模型，通过引入Lagrang。乘子释放系统的约束，列出了由系统的运动微分方程和空间约束代数方程组成的一组微分一代数混合方程组。这种DAE方程组具有很大的刚性，求解时要解决两方面的问题，一方面是由于存在刚性(病态)，在计算过程中随着误差的积累，约束方程的违约加剧。得到的解已经不能表示约束多体系统的真实运动，所以必须对约束方程的违约进行抑制;另一方面是怎样有效地将微分一代数混合方程组化为纯微分方程组，运用求解微分方程组的计算方法求解。 论文主要完成了在已经建立的虚拟轴混联研抛机床多柔体动力学模型基础上，应用牛顿一拉斐逊(Newton一Rophson)数值计算方法求解微分一代数混合方程组，得到3一PTT并联机构动平台、支杆、滑鞍各部件的运动轨迹、速度和加速度变化规律，以及串联机构的姿态变化曲线。继而在虚拟轴混联研抛机床的数学模型中施加一定大小和方向的激振力，通过计算机仿真分析计算机床的振动模态，对机床进行模态分析，对虚拟轴混联研抛机床进行了动力特性研究。仿真实验结果表明，由于机床的铰接特点，支杆在运动中弹性变形很小，其柔性对动平台的轨迹影响不大，而虚拟轴混联研抛机床刚起动时，并联机构的基频容易引起系统的振动，说明机床刚起动时是最不稳定的，存在所谓的起动下冲现象。所以，在研抛加工中，如果避开机床的起动阶段，就可以达到稳定加工过程的目的。最后在虚拟轴混联研抛机床上进行了曲面研抛试验，结果是当3一PTT并联机构的动平台分别沿X向、Y向运动时，Z向累积误差最大值为0.04mm，一次研抛后表面粗糙度Ra值达到0.5林m左右，可以满足研抛加工要求。 为了能更有效地对虚拟轴混联研抛机床进行控制，需要深入地了解其运动学和动力学特性，而逆动力学问题是实现虚拟轴混联研抛机床动态控制的理论基础，对机构进行逆动力学分?更多还原

【Abstract】 The metal cutting machine tool develops until now, in a word their basic construction has no what to change. It is generally adopted the layout of asymmetry "C" to be set up by the bed, the column, the headstock and the table. This kind of layout makes machine tool organization complicated, the being forced deformation and the thermal deformation is asymmetrical and the accumulation error enlarged. However, the virtual axis machine tool (the parallel machine tool) breaks thoroughly since two centuries the principle of the construction for the machine tool and the kinematics, based on the straight-line displacement of Cartesian coordinate. It is combined with the robot technique and the machine tool construction technique. Based on the space parallel mechanism (the parallel robot), the part of hardwares is replaced by the software and the parts of mechanical transmission are replaced by the electrical device and appliance. It has some merit such as the simple construction, the short transmission chain, the good environment adaptability and the high additional value of technology.The virtual axis machine tool is developed for 10 years up to now, many kinds of the constructions of the special machine tool was developed in the world. In it, some have already carried into the practical phrase. Totally, the virtual axis machine tool has the high extent of modularization, apting to reforming and the simple mechanical construction. But the machine tool has also existed some shortages obviously, namely it has the obvious disfigurement in the rigidity, precision and workspace and so on. Therefore, how to develop the new applied field of the virtual axis machine tool by growing the advantage and avoiding the shortage, become the strategy choice, which has the important research value in this field. In the development of the virtual axis hybrid machine tool is developed by our group, the new field of the automatic and precision machining on the mold curved surface is looked for and expanded. To make use of the characteristics of the flexibility machiningwell and to design flexible polishing tool system skillfully, it is applied in the polishing on the free curved surface. The exploration of this paper opens up a new road to develop the applied field of the virtual axis hybrid machine tool.The virtual axis hybrid polishing machine tool is a complex multibody system, which contains many closed-loop chain structures. It is complex and difficult to build the dynamic equations compared with the traditional series mechanism. Different from robots, the virtual axis hybrid polishing machine tool itself has many features in the dynamics aspects. Especially, for such a special machining process of polishing of free-form surfaces, the vibration of the machine and cutting stability is the key problem. So it is the key to analyze the dynamics of the virtual axis hybrid polishing machine tool in order to improve the dynamic characteristics of the system. At present the dynamic equations of virtual axis hybrid polishing machine tool are mostly built by taking the machine tool as rigid multibody system. By the methodology of rigid multibody dynamics, the dynamic equations for each leg and platform can be built by regarding each leg and platform of the virtual axis hybrid polishing machine tool as the independent sub-structure. Then based on the constraint conditions of sub-structure, the constraint dynamic equations for the system are built. Because rigidity of each part is different, for example, the rigidity of each leg is weaker than that of the moving and fixed platform, the deformation of legs can not be ignored during the process of moving. Meanwhile the deformation of each leg is acting or coupling with the rigid movement of the whole virtual axis hybrid polishing machine tool.Based on the above analysis, this paper applies the modeling method of dynamics of flexible multibody systems into the dynamic analysis of virtual axis hybrid polishing machine tool and builds the dynamic equations of spatial rigid-flexible coupling multibody syste更多还原