Development of an Infinite-Stiffness Aerostatic Bearing

两种类型的主动节流器用于获得无限刚度空气静压轴承。主动节流器之一是空气静力控制节流器（ACR），它被纳入一个空气静力推力轴承。止推轴承止推板的直径为65mm。ACR的开度由空气静压轴承控制，并且可以很容易地改变主动节流器的特性，并且可以将轴承刚度调整为无穷大。当供给压力为0.49MPa时，对于小于240N的载荷，轴承的推力刚度可以是无限大的。负推力刚度也可以实现。另一个有效的限流器是排气控制限流器（ECR），它被整合到一个双排空气静压径向轴承中。径向轴承内径为40mm。ECR的开度由微型计算机控制的压电驱动器控制。当供给为0.49MPa时，对于小于70N的载荷，轴承的径向刚度可以是无限大的。这些无限刚度推力轴承和径向轴承组合成一个空气主轴。气主轴轴向旋转精度小于20nm，径向旋转精度小于50nm。载荷为时，也可获得无限刚度

Two types of active restrictors are used for obtaining infinitestiffness aerostatic bearings. One of the active restrictors is an Aerostatically Controlled Restrictor(ACR), which is incorporated into an aerostatic thrust bearing. The diameter of the thrust plate of the thrust bearing is 65mm. Opening of the ACR is controlled by an aerostatic bearing, and the characteristic of the active restrictor can easily be changed, and the bearing stiffness is adjusted to be infinite. When the supply pressure is 0.49MPa, the thrust stiffness of the bearing can be infinite for the load smaller than 240N. Negative thrust stiffness can also be realized. Another active restrictor is an Exhaust Control Restrictor(ECR), which is incorporated into a two-row aerostatic radial bearing. Bore diameter of the radial bearing is 40mm. Opening of the ECR is controlled by a piezoelectric actuator which is controlled by a micro computer. When the supply is 0.49MPa, the radial stiffness of the bearing can be infinite for the load smaller than 70N. These infinite-stiffness thrust bearing and radial bearing are combined to construct an air spindle. Rotational accuracy of the air spindle is less than 20nm in the axial direction, and less than 50nm in the radial direction. Infinite stiffness can also be obtained when the load is