【作者】 王瑞；

【导师】 钟诗胜；

【作者基本信息】 哈尔滨工业大学 ， 机械设计及理论， 2007， 博士

【摘要】 为了实现5坐标加工能力,充分利用大量传统立式铣床的资源,同时积累相应的铣床数控改造的经验,本文提出了两种改造方案,并对方案的可行性及相关理论进行了研究分析,最终采用其中的一种方案,研制出6-TPS并联平台型数控铣床,为以后传统立式铣床的多自由度数控改造提供一种可行方案。建立了6-TPS并联平台型数控铣床需要的三个必要的坐标系(工件、上平台、基座坐标系),给出了坐标系之间的转化关系,采用合适的上平台姿态角表示方法,实现了从刀位文件到最终支路驱动量之间的转变,同时也给出了由支路驱动量到刀具加工点位姿的求解,针对刀位文件速度校验的需要,进行了数控铣床的运动学分析,针对结构参数的设计需要,对铣床进行了姿态灵活度、位置灵活度的推导求解。考虑到倒置和正置式铣床布局结构的不同,采用刀头点在上平台上的可达空间作为铣床的工作空间。为了快速对刀位文件进行校验,本文采用记录不同高度对应的工作空间的内切圆柱体的半径、高度、刀具姿态角,形成相应刀具对应的工作空间表单,利用极坐标求解的方法确定工作空间具有求解速度快,数据存储量小的特点,而且有利于数据量大的刀位文件进行快速校验,提高工作效率。合理设计并联平台的结构参数,在工作空间范围内考虑驱动支路的惯量、上平台质量及主轴质量对动力学性能的影响。针对6-TPS并联平台型铣床刀具刀头点位置参数与并联工作台的结构参数存在较大的耦合性,采用了加权分类隔离的标定方法,把结构参数分为两大类,在工作台上加工一辅助工艺孔,借助该工艺孔,固定一类参数,标定另一类参数,在并联工作台的结构参数标定过程中,采用了二次优化和改进后的共轭梯度法进行标定,提高了标定效率。通过多轮标定,最终可以提供一套结构参数,使其能够保证工件的加工精度,考虑立式铣床的主轴独立于并联平台,获取主轴中心线的倾斜方向角,采用修正刀位文件姿态参数的方法,消除刀具加工过程中可能产生的“搓板”现象。为了改进传统数控软件存在的诸如软件结构复杂、升级困难、不易维护等缺点,考虑目前用软件复用,软件重构等软件开发新技术对开放式数控系统进行研究的趋势,采用了COM组件技术,开发一系列铣床加工需要的底层组件、中间组件,形成由文档与数据库层、中间自动化组件层、上层数控软件应用层组成的三层结构。中间组件层采用了聚合技术,可以实现组件的高效应用,这种结构有利于数控软件的快速并行开发、组件的快速替换、便于升级和维护,可在较高层次上满足开放式数控系统的要求。对第二种数控改造方案XY-RPS型铣床本文第二章也进行了相关理论的分析推导,其中推导出合理的姿态角表示方式,给出了RPS并联机构简洁的约束方程,利用约束方程可以方便地进行运动学分析求解,文章还提出了改进的杆长逼近正解算法,该算法较传统数值算法以及封闭正解算法更加方便快捷。分析了加工过程中离散时间、步长对两种铣床上平台运动性能的影响,另外也对两种方案刀具的工作空间进行了分析比较。本文最终采用6-TPS并联平台型数控铣床作为改造方案,成功实现了铣床必需的手控模块、定位模块、过程监控等模块,完成了铣床50个结构参数的标定工作,验证了各章节理论推导的正确性。更多还原

【Abstract】 In order to achieve the ability of five-axis milling, make full use of traditional milling machines, and gain some experience in amending traditional machines, two kinds of augment schemes are introduced. The feasibilities and correlative theories are discussed in detail. The 6-TPS parallel platform milling machine is designed and fabricated finally.Three coordinate frame(workpiece frame, upper platform frame, base frame) are assigned for the convenience of the programming and calculating, the translation relationships between them are derived. The proper Euler orientation angles are adopted, and the translation from the cutter’s position and orientation in workpiece frame to the lengths of six driven struts is analyzed, while the translation from the latter to the former is also discussed. To satisfy the requirement of the velocity checkout for the cutter location data file(CLDFILE), the kinematics problems of the milling machine are analyzed in detail, and the position sensitivity and orientation sensitivity are derived to optimize the structure parameters of the milling machine.The workspace of traditional Stewart machine tool is the reachable space of the movable platform, but it is not the same in these schemes. In this paper, the reachable space of the cutter in the upper platform frame is considered as the workspace of the milling machine. In order to verify the CLDFILE rapidly, a new approach is adopted. The radius and height parameters of the inscribed cylinder at different cutter tip height are recorded in the data sheet of the workspace database, the cutter oblique angle parameters are also recorded. With the help of these datasheets, the efficiency is improved evidently. On the other hand, the dynamics problems are analyzed with a view to the influence caused by the inertia of six driven struts, mass of upper platform and mass of main axis.Because of the coupling relationships between the cutter position parameters and the structural parameters of parallel mechanism, a new verification approach is necessary. This paper presents an approach adopting classifiable verification with weight value. With the help of a hole with certain radius on the upper platform, the cutter position parameters are coarsely verified using the parameters of parallel mechanism, then the parameters of the latter are also verified using the former. The twice optimization method and amended Fletcher-Reeves algorithm are presented for improving the efficiency of verification. After several rounds verifications, the structural parameters of 6-TPS milling machine are verified to meet the requirement of machining precision. Through amending the orientation parameters of CLDFILE, the phenomenon of“washboard”is disappeared.The paper introduces some problems of traditional NC software, such shortcomings as complex structure, difficult upgrade and difficult maintenance, and presents realizing component programming with the help of COM technique. The new NC software adopted three level structure, including application level, COM components level, database level. The component aggregation technique is introduced, and The NC software data stream among the components is discussed. This software structure is be propitious to the rapid programming, rapid substitution, rapid upgrade of COM component, and meets the requirement of Open NC system.The related theory analyses on XY-RPS milling machine are derived. The paper presents RPS constrain equations, amended forward kinematics solution and compares XY-RPS milling machine with 6-TPS parallel platform milling machine with regard to cutter workspace , kinematics simulation.The 6-TPS parallel platform milling machine is designed and fabricated. Hand-control module, workpiece locating module and trouble hunting module are introduced respectively. The 50 structural parameters are verified successfully and proved the theory validity.更多还原