精密机床结合部非均匀接触对精度稳定性影响机理研究

To obtain the mechanism and law of the machine tool precision stability affected by the non-uniform contact characteristics of joint interface dimensional deviation and normal direction geometric errors including motion and fastening components, it studies the precision time-varying characteristics and nonlinear dimensional changes of the ultra-precision compound micro-machine tool based on the non-uniform contact features. In the research, it is planning to use the methods of NURBS-CAD curved surface modeling, nonlinear characteristic information Entropy, NNI (Nearest Neighbor Index), Coulomb / fractal theory, numerical analysis, FEM(finite element method), and the optimization test of equivalent parts. The research contents focus on machine tool joint surface time-domain changing features including the formation and characterization of non-uniform stress field, non-uniform temperature field change and its heat transfer modeling, the influence of force-temperature effect on the friction time-varying characteristics. To break through the machine tool joint interface key technologies including geometric error modeling, nonlinear error changes prediction and machine tool precision time-varying prediction due to the geometric features, it reveals precision variable mechanism and law of machine tool due to the joint interface geometric error. Then, the temperature/stress/friction-time-precision numerical models will be established to predict the time-varying characteristics of precision stability caused by the geometric errors. Moreover, the results will optimize the design of precision machine tools, and improve the precision stability technology of precision mechanical system.

为获得精密机床运动副和紧固部件结合部的形位误差、结合面法向几何特征误差引起的非均匀接触特性及其对精度稳定性影响机理和规律，针对结合部非均匀接触对机床精度时变特性的影响问题，以超精密微小型数控车铣复合加工机床为研究对象，采用NURBS-CAD曲面建模、非线性特征信息熵、最邻近距离指数评价、库仑/分形评价、数值分析、有限元分析、等效部件优化实验等方法，重点研究机床结合部的非均匀应力场的形成与表征、结合部的非均匀温度场建模及变动特性研究、力热作用的结合部摩擦时变特性等内容，突破机床结合部的几何特征误差曲面建模、形位非线性变动预测和几何特征误差对机床精度时变特性预测等关键技术，揭示结合部几何误差特征造成的机床精度时变机理和规律，构建“温度/应力/摩擦-时间-精度”数值模型，实现结合部几何特征误差引起的机床精度时变特性预测，指导精密机床的精度稳定性优化设计，增进精密机械系统精度稳定性技术体系构建。

机床关键部件结合部和运动副结合面的特征误差是影响精密机床精度稳定性的关键因素，为深入研究精密机床结合部对机床精度稳定性的影响特性，针对精密机床的立柱、导轨滑块等关键结合部的固有加工误差特征，进行误差点的微米级精度采样，采用NURBS数学建模方法进行曲面建模，构建包含几何面特征误差的3D装配模型；基于结合面特征误差模型，分析研究包含特征误差的非均匀接触结合面的应力场非均匀变动特性，获取了具有几何误差特征的结合面应变与预紧力变动关系，该变动关系体现为大斜率线性变化阶段—曲线变化阶段—小斜率线性变化阶段的三阶段特性，揭示了这一变动特性根源于结合面特征误差高点非均匀接触的应变非线性变动的机理，验证了结合面特征误差对机床微米级精度运动系统的稳定性显著影响现象。.同时，为了揭示环境因素对机床精度稳定性的影响量化，首先采用ADAMS数字样机和等效运动副实验平台耦合实验方法，揭示了1Hz以下振动环境下，机床间隙较大的导轨滑块直线运动副振动显著，1Hz以上振动环境下机床整体结构系统振动显著，并附加影响直线导轨运动副的直线运动振形，从而产生精度的非稳定变化。.另外，在非振动因素干扰下，针对精密机床的主轴结构系统，采用结合面误差建模的有限元温度场分析、微纳米多普勒检测和高分辨率红外测温仪检测与标定的耦合分析方法，揭示了0.1℃的温度变化量导致的主轴微纳级精度的变动特性，特别是 0.5℃的温度变化量就很容易引起机床主轴1.0微米以上的精度变动，所以，精密机床主轴的精度稳定性必须具备较好控温条件。.最后，针对市场典型产品系列的精密立式加工中心和龙门镗铣床的结合面精度保持和结构高刚度精度稳定性共性技术问题，采用包含结合面误差特性的有限元模态分析和试验模态分析相结合的方法进行了的结合面接触稳定性和动态刚度优化设计，整体结构系统刚度提高了30%左右，促进了机床低阶频率的提升，从而实现了考虑非均匀结合面误差因素的精密机床结构优化设计技术的良好应用。