Study On Vibration Characteristics Of Two Dimensional Linear Drive Air Bearing Stage Under The Action Of The Gas Flow Field

Air bearing stage driven by linear motor has become the first choice of precision motion platform because of its characteristics of low friction, less transmission links. In most cases, the accuracy of air bearing stag is two orders of magnitude higher than traditional mechanical table. However, the gas film flow field in the vortex and the uneven pressure will cause micro vibration. Although the air bearing stage has been applied to the scanning positioning stage of photoetching machine whose precision is up to 38nm, but with the development of technology, the accuracy requirements of air bearing table continue to increase, the micro vibration phenomenon has become a constraint to a higher level of development of precision with air bearing stage. In this paper, the auther will research on vibration characteristics of air bearing stage under the effect of gas flow field from three aspects as analysis of gas flow field calculation by CFD, vibration analysis of gas flow by harmonic response method, analysis of vibration signal. The main contents as follows.1、The flow field of gas film how to affect the micro vibration of air bearing table is studied from the principle of flow induced vibration. Using single factor analysis method, through the analysis of the flow field of gas film with different orifice structure form, orifice diameter, gas film thickness and gas supply pressure, to research the micro vibration of air bearing table how to be affected by tehthe orifice structure form, orifice diameter, gas film thickness and gas supply pressure.2、The vibration analysis model composed of air bearing stage and gas film is stablished to analyze the vibration resistance of gas film, the gas film stiffness formula is derived, the static stiffness test was carried out on the table to verify the correctness of the gas film stiffness calculation model, according to the corresponding results, the influence factors of gas film vibration resistance are studied.3、The vibration response characteristics of the air bearing stage under the action of gas flow field is studied by modal superposition harmonic response analysis.According to the design requirements of air bearing stage, the maximum vibration amplitude of air bearing stage can not exceed 2 μm. The composition of the air bearing table is optimized according to the harmonic response analysis results, to make the vibration amplitude of air bearing stage meet the precision requirement.4、The vibration signal acquisition system of air bearing stage is established to collect vibration signal of air bearing stage under different gas pressure and film thickness, the influence of gas pressure and film thickness on air bearing stage is studied according to the experiment results to verify the the experiment results. A method of extracting the characteristic parameters of vibration signal by HHT transform is proposed, the characteristic parameters of air bearing table vibration signal are studied through he analysis of IMF component and, the Hilbert spectrum and Hilbert marginal spectrum of vibration signal before and after gas supply.The research work of this paper has revealed the mechanism of micro vibration of air bearing stage caused by the gas flow field, illustrated the factors that influence the micro vibration of air bearing stage, studied on the vibration response of air bearing stage under the action of gas flow field, analyzed the characteristic parameters of vibration signal, to provide a theoretical basis for improving the vibration performance of air bearing stage.