超精密气体静压轴承自激振动机理及抑制方法研究

The proposal is put forward based on specific goal of no.9 cultivation plan of NASF，which study on the impact mechanism of self-excited vibration on ultra-precision aerostatic bearing and its vibration suppression. Aerostatic bearing is the key component of ultra-precision machine tool. However, the existing of self-excited vibration, pneumatic hammer has become one of major factors, which limit further improvement of dynamic performance of aerostatic bearing. The applicant has previously completed the analysis of the static bearing capacity and dynamic rotor accuracy. This project intends to further study the mechanism of pneumatic hammer and its suppression. .The research starts with the simulation of flow pattern by hybrid RANS/LES and update the simulation results by PIV technology. After that, establish the dynamic model of bearing considering the coupling effect between macro vibration and micro flow. The critical condition for occurrence of pneumatic hammer and its nonlinear bifurcation behavior are calculated, which help to reveal the formation, the cause and the development of pneumatic hammer. Finally, study the relationship between design parameters of aerostatic bearing and pneumatic hammer. Several suppression methods of pneumatic hammer are provided including optimization of design parameters and the active passive hybrid control. All the results will be verified by the experiments. .The research results are believed to fight the technology blockade in developed countries. It also provides a theoretical basis, design basis and key technology for development high performance of ultra-precision aerostatic bearing. This research project has a great significance on promoting fundamental theoretical innovation and scientific advances.

本申请针对“培育项目”的明确目标课题-9.超精密气体静压轴承自激振动机理及抑制方法研究。气体静压轴承是超精密加工机床的核心支承部件，但其工作条件下自激振动现象仍未解决，成为制约轴承性能提升的重要瓶颈。申请者前期已经完成了轴承静态承载力、动态回转精度作用规律分析，本项目拟进一步研究气锤自激振动的机理及抑制方法。首先，模拟气锤振动中复杂流场流态，采用新型混合湍流模型计算流场气旋，基于粒子图像测速实验修正仿真结果；之后，研究微观流场至宏观轴承振动的耦合效应，建立气锤振动分析的动力学模型，解析轴承系统的非线性动力学行为，应用分岔理论揭示气锤振动的形成、诱因及发展过程；最后，研究轴承设计参数对气锤振动的影响规律，提出振动抑制的参数优化、主被动控制等多种方法，并搭建实验予以验证。本项目研究为突破国外技术封锁，发展高性能气体静压轴承提供共性基础理论、设计依据和关键技术，具有重要的理论意义和应用价值。

气体静压轴承是超精密加工机床的核心支承部件，但其工作条件下自激振动现象仍未解决，成为制约轴承性能提升的重要瓶颈。本课题主要研究超精密气体静压轴承自激振动的发生机理及其抑制方法。首先，基于混合RANS/LES方法模拟了小孔节流静压止推轴承的内部湍流流场，着重研究了均压腔区域内的气旋等湍流流场流态，获得供气压力对轴承均压腔和气膜流场的影响规律。对多孔质局部微观模型建立及其内流场仿真进行了研究，发现了多孔材料内部的孔隙与喉道的分布决定了材料内部整体流场的分布趋势以及变化规律。其次，借助流固耦合CFD工具实现了微观流场和主轴宏观运动的数据交换，建立了宏微观耦合的气锤振动分析模型，基于该模型得到的自激振动发生机理如下：① 一定的内部气容会导致流场产生复杂的涡旋结构，涡的存在致使节流孔出口附近出现剧烈变化的压力波动，当压力波动频率接近主轴系统的固有频率时易引发了自激振动；② 一定强度的供气压力则进一步激发了压力波动，为整个系统的自激振动形成提供了充足的能量；③自激振动是在一定结构参数和气源参数下形成的复杂流场作用在主轴系统上，从而使内部激励振源振动频率接近了流固耦合作用下的主轴系统固有频率从而引发的共振现象。之后，探究了负载质量、供气压力、节流孔直径、均压腔直径和深度等轴承设计参数对气锤自激振动的影响，得出某型号下不产生气锤自激振动的最大工作临界值：节流孔直径0.15mm，均压腔直径2mm，均压腔深度0.1mm，负载质量36kg，供气压力0.58MPa。通过搭建气锤自激振动实验平台，获得的理论仿真结果和实验结果偏差为7.9%，证明了理论研究的有效性和准确性。项目最后提出采用三种模式的气锤振动抑制方法，周-径向均压腔、氙气润滑介质和磁阻尼设计的方法，理论分析表明可以有效抑制气锤自激振动的发生临界值。