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，需要机床系统在刀具和工件之间产生准确的相对运动，并要求机床各部件的精度提高。本研究提出了一种刀具与工件之间六自由度运动误差测量装置的机床系统。在机床主轴与平面之间安装六足并联机构，由传统机床被动驱动。然后，由于该机构具有Super-Invar杆补偿装置，用于补偿关节和连杆的弹性和热误差，因此六足体可以测量不受温度波动和外力影响的六自由度运动。因此，测量的6自由度误差补偿了刀具的位置和方向。首先，设计了一种由球面关节和带线性刻度单元的移动关节组成的可伸缩连接链（支杆），并进行了实验制造。对球面关节进行了改进，消除了球柄的热变形。此外，在支柱中安装了一个Super-Invar棒补偿装置，并对重力和温度变化的影响进行了测试。结果表明，重力和温度变化对支撑杆长度测量精度影响不大。其次，一个传统的笛卡尔坐标几何机构已经被。该机构采用三个滚珠丝杠驱动的直线定位平台，配有交流伺服电机和旋转编码器。利用激光干涉仪测长系统，测量了表面板与刀具主轴之间的定位误差和运动误差。最后，研究了一种利用冗余无源连接链标定六足机构37个运动参数的方法。六足机构在工作空间内运动时，尺度单元测量的长度变化和运动学计算的长度变化产生了7个支杆长度误差。最小二乘法利用雅可比矩阵对37个参数进行了修正和重复，使长度误差最小。结果表明，得到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