基于自适应测量和实时重构的自由曲面特征产品的逆向研究

Study on the Reverse Free-form Feature of Products Based on the Self-adaptive Measurement and Real-time Reconstruction

为提高自由曲面测量速度和重构精度,基于三坐标测量机CMM,提出自适应测量的曲面重构方法。测量过程中,通过不断拟合样件上已测点,预算待测点及其测量矢量,指导CMM自动采集曲面上数据。由点云拟合自由曲面模型后,检验拟合模型上点与样件上相应点的误差;若误差偏大,则在测量点云中加入检测点后重新拟合曲面,进一步检测重拟合实体模型直至满足精度要求,得到精准数据点和精致的自由曲面模型。辅以计算机图形可视化实例验证本法,测量精度及其重构精度可达μ级,具有自由曲面特征的零部件整个逆向周期呈数量级下降,算法鲁棒性强。

In order to improve the speed and precision for surface measurement and reconstruction,a new method is proposed based on the coordinate measurement machine CMM adaptive measurement method to reconstruct surfaces. In the measurement process,points got from the sample are fitted to calculate the next point and the measurement vector,and guide the CMM to automatically measure. After fitting the free surface model of the measured cloud,the error between points on fitting model and sample is detected and calculated. If the error is big,the actual detected points are added to reconstruct the model again. The accurate data and the elaborate surface model are obtained by detecting and updating the fitted model until the accuracy meets the requirement.Furthermore,a computer graphics display method is used to make the calculation examples process visual to verify the proposed method. The empirical results show that the accuracy of measurement and reconstruction reaches the micrometer level,and the reverse cycle for free form surface is multiply shortening down,and the algorithm robustness is high.