微尺度效应与不平衡耦合作用下空气静压主轴精度评估与智能调控研究

The aerostatic spindle is a key component of ultra-precision machining equipment. Its rotation characteristics are formed by the cross-coupling of the bearing capacity characteristics and the operating characteristics of the rotor, the coupling interaction between the micro-scale effect of the bearing clearance and the unbalance of the moving rotor makes the mechanism of rotation characteristics of spindle very complicated. The influence of micro-scale effect on the flow state of gas film is characterized by the correction of the traditional fluid equation, and the interaction mechanism between the micro-scale impact factors is revealed. The influence of the unbalance factor on the rotation accuracy of the spindle is evaluated by establishing the relationship between the orbit of spindle center and the dynamic radius of the moving rotor. From the theoretical aspect, the characteristic parameters of spindle rotation accuracy are studied to build a coupling model between the micro-scale effect of gas film and the unbalance of the spindle, the relationship between the variation of rotor motion accuracy and the microscopic physical behavior of the gas film is revealed. Based on the optimized rotation accuracy evaluation model of the spindle, the unbalanced feature is extracted and the corresponding unbalanced position is identified and suppressed. The purpose of this research is to further reveal the essence of the coupling interaction between the micro-scale effect and the unbalance by studying the change mechanism of aerostatic spindle rotor state during the working process, conclusively put forward the intelligent regulation device that can effectively adjust and control the spindle rotation accuracy, moreover, this research provides theoretical explanation and technical support for exploring the means to enhance the reliability of intelligent manufacturing.

空气静压主轴是超精密切削加工设备的关键部件，由于空气静压主轴的回转特性是由轴承的承载特性及转子运行特性交叉耦合形成的，而轴承间隙的微尺度效应和转子运行中的不平衡耦合使得主轴回转特性变得非常复杂。本课题通过修正传统流体方程来表征微尺度效应影响的气膜流态，揭示微尺度影响因子之间的相互作用机制；通过建立轴心轨迹与转子动态半径之间的关系来评估不平衡因子对主轴回转精度的影响率；从理论方面研究主轴回转精度的特征参数来构建气膜微尺度效应与主轴不平衡耦合模型，揭示运动过程中转子运动精度变化与气膜微观物理行为的关系；基于优化后的主轴回转精度评估模型实现不平衡特征提取及具体不平衡位置的辨识及抑制。本课题研究的目的是通过研究工作过程中空气静压主轴转子状态变化机理来进一步揭示微尺度效应与不平衡耦合的本质，总结提出能够有效调节控制主轴回转精度及稳定性的智能调控装置，为探索提升智能制造的可靠性提供理论解释及技术支撑。

本项目围绕轴承间隙的微尺度效应和转子运行中的不平衡耦合对空气静压主轴回转特性影响展开研究。通过修正传统流体方程表征出速度滑移、稀薄效应和有效黏度模型，比较忽略微尺度因子时的气膜刚度与考虑单个微尺度因子时的气膜刚度，发现速度滑移对气膜刚度的影响最大，气膜刚度减小了7.8%，流量因子Q对气膜刚度的影响最小，分析多个微尺度因子耦合对气膜刚度的影响，与传统情况下不考虑微尺度效应相比较，考虑三个微尺度因子的耦合作用下，气膜刚度变化最大，气膜刚度降低了25.35%；研究了主轴系统在不平衡因素单独作用、与制造误差和微尺度效应耦合作用下对轴承性能的影响情况，发现在偏心率为0.5附近时承载力最大，偏心率高于0.5时承载力快速下降，以此推断主轴正常运转时的偏心率应控制在0.5以下，当转子偏心和制造误差同时增加一倍时，前者对主轴回转精度的影响大约是后者的2倍；为了有效抑制空气静压主轴的不平衡振动，利用压电陶瓷作为致动器设计了相应的振动抑制装置，采用前馈结合反馈的方式以及变结构滑模控制对空气静压主轴系统的不平衡振动进行了有效抑制，使得主轴整体回转精度提高50%以上，本课题还提出了一种带弹性元件节流器的轴承来改善整体性能，带弹性元件的空气静压轴承的承载力和刚度都有明显提高，通过对比得出该弹性系统使得空气主轴回转稳定性提高20%以上；本项目最后以刀具和工件所组成的切削系统以及空气静压主轴系统为研究对象，研究了切削过程阻尼影响下的主轴系统动力学特性及其对超精密切削加工表面形貌生成的影响，建立的考虑过程阻尼影响的主轴动力学特性影响下工件表面形貌同实验结果之间的误差仅为不考虑过程阻尼影响的传统模型的50%左右，证明了基于考虑过程阻尼影响的主轴动力学特性所得到的表面形貌更符合实际加工结果。以上研究结果揭示了空气静压主轴微尺度效应与不平衡耦合的本质，为探索提升高端装备的精度及可靠性提供理论解释及技术支撑。