Development of an Infinite-Stiffness Aerostatic Bearing

为了获得无限大的空气静压轴承，使用了两种类型的主动限流器。其中一种主动限制器是空气静压可控限制器(ACR)，它被集成到空气静压推力轴承中。推力轴承推力板直径为65 mm。ACR的开度由空气静压轴承控制，主动限流器的特性可以很容易地改变，轴承刚度可以调整到无限大。当供气压力为0.49 Mpa时，当载荷小于240N时，轴承的推力刚度可为无穷大。还可以实现负推力刚度。另一个主动限制器是排气控制限制器(ECR)，它被集成到两列空气静压径向轴承中。径向轴承的内径为40 mm。ECR的开启由微型计算机控制的压电式致动器控制。当供给量为0.49 Mpa时，当载荷小于70N时，轴承的径向刚度可为无穷大。这些无限刚度推力轴承和径向轴承组合在一起，构成了一个空气主轴。气轴轴向回转精度小于20 nm，径向回转精度小于50 nm。当荷载是时，也可以获得无限的刚度

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