流量制御弁による空気静圧軸受の変位フィードバック制御の試み

抄録

The machine tool spindles supported by aerostatic bearings are a core component that determines machining accuracy of the ultra-precision machine tools. Typical desired level of the machining accuracy reaches submicron in the ultra-precision machining. However, there is some difficulties to satisfy the requirement, because of the thermal deformation by the heat generation during high-speed rotation of the spindle and low bearing stiffness due to the compressibility of air. In order to compensate the problems concerning the aerostatic bearings, the displacement control system of the aerostatic thrust bearings is designed in this study. The displacement control is made by controlling air flow into the bearings using a proportional flow control valve. A conventional feedback control system is designed based on a derived mathematical model. Performances of the designed feedback control system are experimentally examined in terms of the static and dynamic characteristics of the system. It was verified that the designed control system is able to control the displacement of the spindle with the positioning accuracy of 6 nm in the range of 0.0 to 10.0 μm. Step response of the system indicated that the settling time of the control system was over 10 seconds that will be reduced by further improvement of the controller.