Study Of Static And Dynamic Characteristics Of Planar Aerostatic Bearings

Aerostatic bearing is widely used in the motion guide components of ultra-speed andultra-precision equipment, due to the advantages of friction-free, high speed and highprecision etc. However, aerostatic bearing has a lower load stiffness, lower damping, and badstability, which limits its application. Subjects of improving the load capacity and stiffness,achieving higher accuracy and stability, have been researched deeply and widely by domesticand foreign scholars. Researches on the static and dynamic characteristics of aerostaticbearings focus on inherent restrictor and orifice-type restrictor at present. However, theresearches of static and dynamic characteristics of the planar aerostatic bearing with orificerestrictors periodically distributed in the circumferential direction are rarely seen. So, thisthesis focuses on the numerical method for the analysis of static and dynamic characteristicsof the planar aerostatic bearing. Influences of bearing parameters on its static and dynamiccharacteristics are investigated.A one-dimensional compressible isentropic flow model is established to describe theflow from the air supply system to the orifice restrictor, and the Reynolds equationsgoverning the pressure distribution in the air gap of the bearing is also derived. Based on theprinciple of mass flow rate conservation and successive over-relaxation iterative numericalmethod, the pressure distribution in the air gap is obtained numerically. The static loadcapacity and stiffness are thus obtained, and the influences of the geometric parameters andtechnical parameters on the static characteristics are analyzed.Based on the static characteristics analysis, the perturbation method is applied on thestatic Reynolds equations to obtain the dynamic Reynolds equations. The approach is thusderived to calculating the dynamic stiffness and dynamic damping coefficients of the planaraerostatic bearing with orifice restrictors periodically distributed in the circumferentialdirection. The dynamic pressure distribution is calculated using the finite difference method.Effects of air gap thickness, air supply pressure and perturbation frequency on the dynamicstiffness and dynamic damping coefficients, as well as stability of the bearing, are analyzed. The testing results of aerostatic bearing system are obtained, the accuracy of ourmathematic model and numerical computing methods are confirmed. Application of themathematic model and numerical computing methods for dynamic characteristic arereasonable.