搭建了非接触式的三坐标测量系统以便精密测量三维型面.将激光位移传感器通过具有两个回转轴的回转体安装在测量机的Z轴上,从而可根据待测表面的形状来调整传感器的方位.为了使传感器在各个方位上实现测量功能,提出了基于球形目标的光束方向标定方法,并详细阐述了其数学原理.标定时,驱动测量机使传感器分别沿测量机的X,Y和Z轴做等间距步进,根据步长和激光束长度的变化建立方程组求解出激光束所在直线的单位方向向量.最后,多次测量尺寸参数已知的六面体标准块规,检验了该测量系统的重复性.结果显示,该系统的测量不确定度为0.048 mm;测量另一直径已知的被测球时,传感器在各个方位上的误差小于0.05 mm,表明所提出的标定方法使测量系统达到了逆向工程的使用要求.得到的数据表明,本文所提出的方法有较高的标定精度和较好的重复性,为实现三维型面的快速扫描测量奠定了基础.

A non-contact three coordinate measuring system was established to implement the measurement of 3D free-form surfaces accurately.A laser sensor was installed on the Z axis of a coordinate measuring machine via a probe head with two rotary axes,whose direction could be adjusted according to the shape of the measured surface.For the purpose of enabling the sensor to realize measurement functions in every orientations,a calibration method of laser beam direction based on a spherical target was proposed,and its principle was analyzed in detail.In the calibration procedure,the sensor moved in an equal distance along X,Y and Z axes and then equation sets were set up based on the bundle equations to compute the unit direction vector of the laser beam.Finally,a cube block with known dimensions was measured by the system to test the repeatability of the measuring system.The experimental result indicates that the measuring uncertainty of the system is 0.048 mm,which shows the good practicability of the calibration method.When the system was used to measure a sphere with a known diameter,the errors in every orientations are all smaller than 0.05 mm,which manifests that the calibration method proposed meets the requirements of reverse engineering.The method shows higher calibration precision and repeatability,and lays a basis for fast scanning of 3D free-form surfaces.