自由曲面轮廓度误差评定及不确定度分析

Evaluation of free-form surface profile error and analysis of uncertainty

针对自由曲面轮廓度误差的评定提出了新的方法,利用实际曲面的重构模型和理论设计模型比较,判断误差是否在要求的公差带范围内。评定的过程为利用三坐标测量机(CMM)在实际加工曲面上获得离散的测点坐标;通过求解最优化问题找到变换矩阵的参数值,将测点从测量坐标系下变换到设计坐标系;利用定位后的测量点坐标,采用B样条插值的方法重构曲面。由于存在测量不确定度,误差评定的最终结果也存在不确定度。针对"S"形试件这类自由曲面,对提出的误差评定方法进行了验证,并且分析了在评定过程中定位误差。重构误差和轮廓度误差的不确定度。实验结果表明,本方法能够客观指导自由曲面加工质量的评价与验收。

A new method to evaluate the free-form surface error is proposed in this paper.Testing whether the error is within the required tolerance zone is implemented by comparing the reconstructed machined surface with the design surface.The inspection process is created out by these steps: acquisition of measurement points on the actual surface,transform the measurement points from the measurement coordinate system to design coordinate system by location; the machined surface is reconstructed by the located points based on B-spline interpolation; the reconstructed surface is compared with the design surface.Because of the uncertainty in measurement process,the uncertainty of location,reconstruction,and form error are analyzed.The proposed method is verified in the measuring and analysis of 'S'shape test shape.The results show that the proposed method is effective to guide the evaluation and acceptance of free form surface machining quality.