基于激光干涉法的大型工件内径测量系统设计

Design of inner diameter measurement system for large workpieces based on laser interferometry

当利用激光干涉法对大型工件进行现场测量时,需铺设长行程直线导轨,导致测量系统结构复杂;为解决该问题,采用模块化接杆式结构的可伸缩测量臂,设计了一套基于激光干涉位移测量的大型工件内径测量系统。该系统由位移测量模块、旋转驱动模块和数据获取与处理模块三部分组成;位移测量模块的测量臂采用双支撑外径递减式结构,有效减少了大尺寸测量时的弯曲变形;采用Pratt法与LM法相结合的融合法进行最小二乘法圆拟合,精确得到被测工件半径和圆度等参数。对研制系统装置进行了定心实验、系统静态稳定性实验、实际工件内径测量及重复性实验等,重复性测量实验测得同一圆周的半径和圆度标准偏差分别为17.60、25.48μm,不同圆周的半径和圆度标准偏差在几十微米内波动,符合测量工件的加工精度。结果表明该系统可应用于大型工件的现场测量,可有效检测和评估工件内径和圆度等参数。

When laser interferometry is used to measure large workpieces on-site,it is necessary to lay long-stroke linear guide rails,making the structure of the measurement system become complex.To solve this problem,a retractable measuring arm with a modular post-rod structure was used in this paper to design a large workpiece inner diameter measurement system based on the laser interferometric displacement measurement.The system consists of a displacement measurement module,a rotation driven module and a data acquisition and processing module.A double-supported outer diameter decreasing structure was used in the measurement arm of the displacement measurement module,which effectively reduced the bending deformation during large-scale measurement.The hybrid circle fitting algorithm combining the Pratt method and the LM method was used to carry out the least squares circle fitting,and accurate parameters such as the radius and roundness of the measured workpiece were obtained.The centering experiment,the static stability experiment,the inner diameter measurement of the actual workpiece and the repeatability experiment of the designed system were carried out.The repeatability experiment showed that the standard deviations of the radius and roundness of the same circle were 17.60μm and 25.48μm,respectively,and the standard deviations of the radius and roundness of four different circles were tens of microns,which were consistent with the machining accuracy of the workpiece,demonstrating the feasibility and effectiveness of the developed measurement system.The results have shown that the system can be applied to the on-site measurement of large workpieces,and can effectively detect and evaluate parameters such as the inner diameter and roundness of the workpiece.