气膜孔视觉测量中的坐标系建立与转换

Establishment and Conversion of Coordinate Systems in Vision Measurement of Film Cooling Holes

为了能够应用所搭建的四轴视觉坐标测量系统对批量气膜孔的分布位置进行检测,结合四轴运动系统与工业相机的特点,开展了将测量数据由图像空间转化到叶片空间过程中的坐标系建立与转换关系研究。在应用过程中,建立了图像像素坐标系、图像物理坐标系、基准坐标系、回转台坐标系和叶片坐标系,并确立了这些坐标系之间的相互转换关系,从而实现了将工业相机所采集到的图像数据转化成物理测量数据,并最终转换到叶片坐标系中。最后,为了验证该方法的正确性和有效性,选取了某个高压涡轮导向叶片作为被测物,首先对其上的一个气膜孔进行了分布位置的多次等精度重复测量实验,检验了该测量系统的重复性精度,而后对该叶片上的一排12个气膜孔进行了测量实验。实验结果表明,本文所提出的坐标系建立与转换方法,可以完成气膜孔分布位置的检测任务,从而为后续与气膜孔的设计数据进行比对并做出评价奠定了坚实基础。

To deal with the difficulties of inspecting the distributions and positions of film cooling holes by the 4-axis vision coordinate measuring system built up,methods of establishment and conversion of coordinate systems in translating the measuring data from image space to blade space are studied,based on the combination of characteristics of the 4-axis motion system and the industrial CCD.In the measuring procedure,image pixel coordinate system,image physics coordinate system,reference coordinate system,turntable coordinate system and blade coordinate system are established and determined respectively,as well as the conversion relationships among them,which helps to transform the image data acquired by the industrial CCD to the physical measuring data in the blade coordinate system.Finally,to verify the validity and effectiveness of the methods proposed in the paper,the locations of a row of film cooling holes on a high-pressure turbine blade selected are inspected on the system.As the experimental results show,the establishment and conversion methods of coordinate systems put forward could be utilized to fulfill the inspecting assignment of film cooling holes,which could serve as a solid foundation for the subsequent comparison with the design data and quality evaluation.