【作者】 徐冠军；

【导师】 黄玉美；

【作者基本信息】 西安理工大学 ， 机械制造及其自动化， 2008， 硕士

【摘要】 混联机床是近年来发展起来的一种新型机床,该类机床采用了串并联复合机构,不仅继承了并联机床高刚度、高精度和高进给速度等优点,还具备了串联机床大移动行程和大旋转运动角的特点。混联机床的出现是机床产业的一次重大革命,代表了新一代机床的发展方向,但加工精度仍是制约混联机床商品化和在工业生产中推广应用的重要因素,如何提高混联机床的加工精度已经成了其能否投入工业运行的关键。运动学标定是提高混联机床几何精度的一种高效、低成本的方法。本文结合6PM2六轴混联数控镗铣床,分析了混联机床并联机构的几何误差来源;建立了空间坐标系,采用坐标变换的方法对动平台的位姿进行了描述;应用逆解模型构造动平台的位姿误差与结构几何误差之间的关系,建立了几何参数辨识模型;以并联杆初始杆长参数的标定为例,测量动平台的位姿信息,将结构参数作为未知数对辨识方程进行求解,得到了并联杆初始杆长的真实值。最后,对并联机构的控制模型参数进行修正,初步完成了混联机床的运动学标定。以内球面加工为例,验证了混联机床运动学标定的有效性。分析内球面的生成原理,采用圆柱铣刀插补内球面截面圆弧与工件绕其自身轴线旋转的运动配合方法进行加工。论述了内球面加工时铣刀与已加工表面发生干涉的可能性,推导了主轴倾角的最小值公式。应用数据采样法内接弦线圆弧插补的方法对内球面截面圆弧进行粗插补运算,精插补则由多轴运动控制器PMAC自身的插补运动模式来实现。更多还原

【Abstract】 The hybrid machine tool is a novel type machine tool developed in the recent years. It is combined serial mechanism with parallel mechanism so that it can obtains the advantages of great travel and rotational angle of the serial parts, as well as high stiffness, high accuracy and high feed speed of the parallel parts. The birth of the hybrid machine tool is a great revolution of the machine tool industry, which also represents the development trend of the new generation machine tool. However, the machining accuracy still is an important factor which restricts the commercialization of the hybrid machine tool and its popularization and application in industrial production. In this case, how to improve the machining accuracy of the hybrid machine tool has become the key that relates to that whether it can be put into practice or not.The Kinematic Calibration is a high-efficiency and low-cost method that can improve the geometric accuracy of the hybrid machine tool. In this thesis, the Geometric error sources of the six-axis hybrid boring and milling NC machine tool 6PM2’s parallel mechanism are analyzed. Space coordinate systems are established, and then the posture of the motion platform is described with the solution of coordinate transformation. Then, the geometric parameters’ identification model is constructed according to the relationship between the posture errors of the motion platform and the geometric errors that is given out by the inverse model. With the calibration of parallel bars’ original length being taken for instance, the posture information of the motion platform is measured and the identification equations are solved by considering the structural parameters as unknowns so that the real value of the parallel bars’ original length can be obtained. Finally, the control model parameters of the parallel mechanism are corrected. In this way, the kinematic calibration of the hybrid machine tool is preliminarily accomplished.With the machining of internal spherical surface being taken for example, the kinematic calibration of the hybrid machine tool is proved effectively. The generating principle of internal spherical surface is analyzed, based on which the machining method of combining the motion of cylinder milling cutter interpolating the section circular arc of the internal spherical surface with the motion of the workpiece rotating on its own axis is chosen. As it is possible that the milling cutter would interfere with the machined surface while machining the internal spherical surface, the minimum value formula of the spindle’s inclination angle is deduced. The time-slicing circular interpolating method is used to accomplish the rough interpolation of the section circular arc of the internal spherical surface, while a certain motion mode of the multi-axis motion controller PMAC is used for the precise interpolation.更多还原