In this paper, we propose a precise linear motion stage supported by magnetically preloaded air bearings. The eight aero static bearings with rectangular carbon porous pads were located only one side of vertical direction under the platen where four bearings are in both sides of horizontal direction as wrap-around-design, and this gives simpler configuration than which constrained by air bearings for all direction. Each of the magnetic actuators has a permanent magnet generating static magnetic flux for required preload and a coil to perturb the magnetic force resulting adjustment of air￢bearing clearance. The characteristics of porous aero static bearing are analyzed by numerical analysis, and analytic magnetic circuit model is driven for magnetic actuator to calculate preload and variation of force due to current. A l-axis linear stage motorized with a core less linear motor and a linear encoder was designed and built to verify this design concept. The load capacity, stiffness and preload force were examined and compared with analysis. With the active magnetic preloading actuators controlled with DSP board and PWM power amplifiers, the active on-line adjusting tests about the vertical, pitching and rolling motion were performed. It was shown that motion control for three DOF motions were linear and independent after calibration of the control gains.
