A novel modelling method of geometric errors for precision assembly
A novel modelling method of geometric errors for precision assembly
复制标题
一种新的精密装配几何误差建模方法
DOI：
10.1007/s00170-017-0936-3
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发表时间：
2018-01-01
影响因子：
3.4
通讯作者：
Zhang, Qiushuang
中科院分区：
文献类型：
--
作者：
Zhang, Zhongqing;Zhang, Zhijing;Zhang, Qiushuang
几何误差在加工零件时是不可避免的，对机械系统的装配质量和精度有很大的影响。几何误差建模是预测几何误差对装配质量影响的关键问题。虽然已经提出了各种几何误差的表示和分析方法，但大多数都只考虑了方位和位置偏差，而没有考虑形状误差。然而，在机械系统中，由于零件表面形状误差的高度分布不均匀，必然导致接触状态的不均匀，进而导致局部表面变形和接触面上的应力不均匀，即使是很小的形状误差也会在装配零件中传播和积累，从而导致故障和降低装配精度的稳定性。提出了一种基于非均匀有理B-Splines(NURBS)曲面的几何误差表示方法，该方法可以考虑形状误差并刻画加工曲面上几何误差的高度分布。加工特征模型(MCM)通过对多个几何误差曲面模型进行平均，建立了表示在同一加工工艺下被加工曲面上几何误差分布特征的模型。所建立的几何误差数学模型可以在计算机辅助设计(CAD)系统中实现，从而提出了一种将几何误差集成到CAD模型中的方法。生成的实体模型(即逼真的几何实体模型)是考虑几何误差的零件几何表示。通过对真实感几何实体模型的相对定位，建立真实感装配模型，实现了机械装配虚拟建模中考虑零件几何误差的目的。实验研究验证了该方法的有效性和可行性。
Geometric errors are inevitably observable on machining parts and have huge influences on the assembly quality and precision of mechanical system. The modelling of geometric errors is the key issue for the prediction of their effects on the assembly quality. Although various approaches for the representation and analysis of geometric errors have been proposed, most of them only consider orientation and position deviations but do not consider form errors. However, in mechanical system, since the non-uniform distribution of the altitudes of form errors on parts surface inevitably leads to non-uniform contact states, further causing the local surface deformations and non-uniform stresses on contact surfaces, even very small form errors propagate and accumulate through assembly parts and lead to malfunction as well as decreased assembly accuracy stability. The paper proposes a method for the representation of geometric errors based on Non-Uniform Rational B-Splines (NURBS) surface, which can consider form errors and characterize the altitude distribution of geometric errors on the machined surface. Machining Characteristic Model (MCM), representing the distribution characteristics of geometric errors on the surfaces machined under the same machining process, is established by averaging a number of surface models of geometric errors. The developed mathematical models of geometric errors can be implemented in COMPUTER-AIDED DESIGN (CAD) system so that a method to integrate geometric errors in CAD model is presented. The resulting solid model (i.e. REALISTIC GEOMETRIC SOLID MODEL) is the representation of parts geometry considering geometric errors. Realistic assembly model is established through the relative positioning of REALISTIC GEOMETRIC SOLID MODELS, which realizes the consideration of parts geometric errors in the virtual modelling of mechanical assembly. The efficiency and feasibility of the proposed methods are verified in the experimental study.