拟合精度约束下航发叶片在机测量采样策略

Sampling strategy for on-machine measurement of aero-engine blade under constraint of fitting accuracy

测量点数量是影响航空发动机叶片复杂曲面在机测量效率的关键因素,为了在满足拟合精度要求的情况下最少化测量点数量,提出了一种考虑拟合精度的叶片在机测量采样方法。首先,根据叶身曲面测量的评价特点,将评价曲面的拟合精度降维成评价一组截面轮廓的拟合精度,建立了度量不同拟合曲线之间误差关系的模型。接着,使用放缩变换从误差关系模型中剥离出拟合误差,并推导出拟合误差的上界模型。进一步以拟合误差上界满足给定拟合允差为约束,依据逼近误差原理迭代计算出最少测量点数量。最后,选择离心式叶轮为对象,在保证在机测量结果拟合精度要求的前提下,验证了此方法能够减少测量点数量以提升测量效率,这为优化曲面类零件的在机测量工艺提供了一种新方法。

The number of measurement points is a key factor impacting the on-machine measurement efficiency of complex surfaces on aero-engine blades.To minimize the number of measurement points while meeting the fitting ac⁃curacy requirements,a sampling approach for blade on-machine measurement that considers the fitting accuracy is proposed.Firstly,in terms of the evaluation characteristics of surfaces inspection on blade body,the evaluation of fit⁃ting accuracy of surfaces is simplified to the evaluation of fitting accuracy for a set of section profile curves,and a model to assess the error relationship between different fitting curves is established.Then,the fitting error is separated from the on-machine measurement results by using the scaling transformation,and the upper bound model of fitting er⁃ror is established.Furthermore,with the constraint that the upper bound of the fitting error satisfies the given fitting tol⁃erance,the minimum number of measurement points is calculated iteratively based on the approximation error prin⁃ciple.Finally,taking the centrifugal impeller as the verification object,the number of measurement points can be re⁃duced,and the measurement efficiency can be improved by the proposed method while ensuring the fitting accuracy of the on-machine measurement results,which provides a new approach to optimize the on-machine measurement process for the curved surface parts.