Development of nanometer-order ultra-precision machine for realizing six-degree-of-freedom perfect relative motion between workpiece and tool

为了实现超精密加工或测量，需要一个能够精确地产生刀具与工件之间相对运动的机床系统，以及提高机床各部件的精度。本研究提出一种使用测量装置的六自由度（6-DOF）的工具和工件之间的运动误差的机器系统。一个六足式并联运动机构安装在工具主轴和平台之间，由传统的机器被动驱动。然后，六足测量6自由度的运动，而不管温度波动和外力，因为该机构具有一个补偿装置与超级因瓦杆的弹性和热误差的关节和连杆。因此，测量的6-DOF误差补偿了工具位置和方向。首先，设计并实验了一种由球铰和带线性比例单元的棱柱铰组成的可伸缩连接链（支柱 ...更多信息 制造的。对球铰进行了改进，消除了球柄的热变形。此外，一个补偿装置与超级因瓦杆已安装在支柱，并进行了测试，调查重力和温度变化的影响。结果表明，重力和温度变化对撑杆长度测量精度的影响很小。第二，传统的笛卡尔坐标几何机制。该机构采用三个滚珠丝杠驱动的直线定位阶段，配备了交流伺服电机和旋转编码器。利用激光干涉测长系统测量了平台与刀具主轴之间的定位误差和运动误差。最后，提出了一种冗余被动连接链标定方法，对六足机构的37个运动学参数进行了标定。利用比例尺测量的长度变化量和运动学计算的长度变化量，推导出六足机构在工作空间内运动时支杆的七种长度误差。利用雅可比矩阵的最小二乘法对37个参数进行修正，并重复修正，使长度误差最小。结果表明，所获得的参数减小了机构的定位误差。少

To realize ultra precise machining or measurement, a machine system generating accurately relative motion between its tool and the workpiece is required as well as the accuracy improvements of each element of the machine. This research proposes a machine system using a measurement device for six-degree-of-freedom (6-DOF) motion errors between the tool and the workpiece. A hexapod-type parallel kinematics mechanism installed between the tool spindle and the surface plate is passively actuated by a conventional machine. Then, the hexapod measures the 6-DOF motions regardless with temperature fluctuation and external forces because the mechanism has a compensation device with Super-Invar rods for elastic and thermal errors of the joints and the links. Therefore, the measured 6-DOF errors compensate the tool position and orientation. First, an extensible connecting chain (strut) consisting of spherical joints and a prismatic joint with a linear scale unit has been designed and experimental … More ly manufactured. The spherical joint has been improved to eliminate thermal deformation of its ball shanks. Moreover, a compensation device with Super-Invar rods has been installed in the strut, and tested for investigating effects of the gravity and temperature change. As a result, the gravity and the temperature change have little effect on length measurement accuracy of the strut. Second, a conventional Cartesian-coordinate-geometry mechanism has been. The mechanism employs three ball-screw-driven linear positioning stages equipped with AC servomotors and rotary encoders. Positioning errors and motion errors between the surface plate and the tool spindle have been measured by using a laser interferometer length measurement system. Finally, a calibration method with a redundant passive connecting chain has been investigated for identifying 37 kinematics parameters for the hexapod mechanism. Length changes measured by the scale unit and changes calculated by the kinematics derive seven length errors of strut when the hexapod mechanism moves in its workspace. The least square method using Jacobian matrix corrects the 37 parameters and repeated so that the length errors are minimized. As a result, obtained parameters decreased positioning errors of the mechanism. Less