Dynamic Analysis of Aerostatic Guideway and FEA Model Development

摘要

A dynamically optimal design is essential for a motion system to perform high speed operation without compromising its accuracy, settling time and vibration specification. Good design practice which accounts for dynamic characteristics in the modelling of a motion system warrants higher performance precision machines and cuts down redevelopment effort to ‘patch’ inherent shortcoming of the machine dynamics.This research aimed to accurately describe the non-linear dynamics of a non-mechanical contact aerostatic guideway system in order to achieve an accurate FEA model of the design stage. The single axis aerostatic guideway is comprised of several machine in¬terfaces that impact the dynamic behaviour of the guideway. Modelling each air bear¬ing pad by a single stiffness element is not adequate to predict the guideway modal behaviour accurately. The aerostatic guideway has been broken down into several key machine interface elements. In-depth investigation of the air film and the air bearing mounting mechanism was carried out. A dedicated air film test rig was designed and built to acquire insight of the air film dynamic characteristics.It is observed that the mounting mechanism of the air bearing constitutes to a signifi-cant dynamic effect to the entire air bearing setup. Based on the findings of the mount-ing mechanism’s stiffness properties, a method was developed to estimate ‘true’ air gap heights which cannot be easily assessed and measured directly in most aerostatic guideway carriages. The estimation method enables a more rigorous FE model of the aerostatic guideway system. The comprehensive dynamic analysis methodology pro-posed in this research greatly increases the confidence and accuracy of the aerostatic guideway’s FE model.