氣靜壓軸承節流器之設計與分析

Abstract

軸承是工具機裡相當重要的元件，從以前到現在，大家已花了很多心思在如何提升軸承性能，按照間隙填充物軸承種類大致上可分滾珠軸承、滾針軸承、液膜軸承、氣體軸承、磁浮軸承。其中氣體軸承屬於超精密檢測設備、超精密加工、和高剛度不足的缺點。因為氣浮軸承其本身之優點相當誘人，即便它已經發展了很多年，最近仍有許多國內外大學、機構的相關人員繼續研究，但考量於某些條件，在其建立物理系統時都做了相當的簡化，這些簡化可能使得系統的細部外觀遭到抹平，因此本研究藉由計算流體力學軟體來比較，看是否能夠不失真的描述系統。而且，本研究在節流器裡加入膜片，從而比較是否對軸承的性能表現有所增益。本研究使用有限元素套裝軟體與工程計算，建立流固藕合模型，進行模擬分析，探討氣體軸承設計的承載力和剛性。推導氣浮軸承的可控制性矩陣以及可觀察性矩陣，最後再加入壓電致動器以達到氣浮節流器的控制，經由FFT分析，發現加入控制器能改善系統。荷重干擾測試也顯示PI控制器下的壓電致動器發揮了作用。

Bearing is a key element of equipments. People have already taken lots of efforts to promote the performance of bearings. According to the material between the bearing and shaft, major types of bearings include ball bearing, needle bearing, fluid bearing, air bearing, and magnetic bearing. Air bearings belong to key components in ultra-precision inspection and testing equipment, ultra-precision machining, and high-speed rotor bearings. However, they have a shortcoming of insufficient stiffness since gas viscosity is simply one thousandth of liquid viscosity. Because the advantages of air bearing itself are attractive, though it’s been developed for many years, there are still many researchers doing this kind of research, including industrial organizations and schools. But for some considerations, we often make assumptions to simplify the system of this physical phenomenon. Will these assumptions lose some important characteristics or not in the true physical system? So we use CFD software to compare the results with those derived based on those assumptions. This study uses CFD software to investigate bearing performance. We further added diaphrams to the restrictor, to investigate diaphragm effects on the air bearing. Based on the finite element method and engineering calculation, this study built fluid-structure interface models to carry out novel bearing design and calculation of loading capacity and stiffness. Controllability and observability of air bearings are derived. Eventually, using a piezo actuator controls the restrictor of the air bearing. Adding controller can make the system better according to FFT analysis results. Loading disturbance test also showed effective function of the piezoelectric actuator under a PI controller.