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为了完成三维型面的高效扫描测量,将激光测头通过回转台安装在三坐标测量机Z轴的移动末端上,以搭建非接触式的光学坐标测量系统。在被测表面三维点云的创建过程中,需要将激光测头的一维距离值转化为测量点的三维坐标值,为此,提出了基于球面的光束空间矢量标定方法。在标定过程中,通过控制测量机X、Y和Z轴的运动实现测头的标定轨迹,使测头能够采集到球面上的若干测量点,同时记录下各轴的光栅尺读数和测头的输出。然后,应用这些数据和球面的约束方程来建立超定非线性方程组,并采用矩阵最小二乘法求解出测量光束所在直线的单位方向向量。最后,将一个直径已知的金属球作为被测对象,应用所搭建的测量系统在10个不同方位对其直径进行测量,所得结果的测量误差均小于0.05 mm,充分说明了所提出的标定方法的有效性,从而为实现空间自由曲面的精密高效测量奠定了基础。
In order to accomplish the efficient scanning measurement of the three-dimensional profile, the laser probe is mounted on the moving end of the Z-axis of the CMM through a rotary table to build a non-contact optical coordinate measuring system. In the process of creating the three-dimensional point cloud of the measured surface, the one-dimensional distance of the laser probe needs to be transformed into the three-dimensional coordinate of the measuring point. For this reason, a spherical-based beam vector calibration method is proposed. During the calibration process, the calibration path of the probe is controlled by controlling the movements of the X, Y and Z axes of the measuring machine so as to enable the probe to collect several measurement points on the spherical surface and record the grating ruler reading of each axis and the Output. Then, these data and the spherical constraint equations are used to establish overdetermined nonlinear equations and the matrix direction least squares method is used to solve the unit direction vector of the line where the measuring beam is located. Finally, a metal ball with a known diameter is taken as the object to be measured, and the diameter of the measured metal ball is measured in 10 different directions using the measurement system set up. The measurement errors of the obtained results are less than 0.05 mm, which fully demonstrate the proposed calibration method So as to lay a solid foundation for the accurate and efficient measurement of space freeform surface.