Modeling, Analysis And Control Of A Gas-lubricated Precision Positioning Stage

Aerostatic bearings have been widely used in various felds (e.g.,precision pro-cessing,electronic manufacturing and ultra-precision measurement devices) for theiradvantages including high speed, high accuracy, wear-free and clean lubrication. Anew method is proposed in this thesis for analyses on static and dynamic performancesofaerostaticbearing,basedonwhichanactivecontrolstrategyisfurtherpresented. Ex-periment systems were then developed where precision positioning and synchronizedcontrol were accomplished by the implementation of aerostatic bearings.Firstly,a numeric computation method based on Diferential Quadrature Meth-ods(DQM) is proposed to study the static performance of aerostatic bearings.Resultsshowed that both computation efciency and accuracy can be improved by the pro-posed method. Moreover, multi-domain computation, smooth approximation are alsoincorporated for more complex problems (e.g.,grooves and multi-feedhole).Secondly, for dynamic problems,DQM were used again, based on which anothernumerical method is developed. With this method, dynamic performances of aero-static bearings were studied. Stability analysis were subsequently developed, where astability criteria based on peak-peak amplitude is further proposed. Results were thendemonstrated by corresponding dynamic experiments.Morover,a gas-lubricated precision positioning stage is designed and presentedin this thesis. A dynamic model of such a stage is proposed based on the aforemen-tioned analysis. This dynamic model is then identifed. A perturbation observer issubsequently proposed for the purpose of positioning control. High precision of thedesigned stage is further demonstrated by corresponding experiments.Finally, active control is utilized in the positioning stage to reject position fuctu- ation along Zaxis. precision positioning along Zaxis is also enabled by such method.