The high precision linear motion table with a novel rare earth permanent magnet biased magnetic bearing suspension

An electromagnetic bearing needs large amount of bias current to support its own weight so that its load capacity is limited and problems caused by heat generation can be arose. In order to remove these drawbacks of the electromagnetic bearing, we developed a novel permanent magnet biased electromagnetic bearing using a rare earth permanent magnet. The permanent magnet provides a bias flux and generates a bias force. The electromagnet can increase or reduce a flux of the permanent magnet and the flux path of the electromagnet does not pass through the permanent magnet that the permanent magnet will not be demagnetized. One actuator can support one control axis and it is composed of one electromagnet and two permanent magnets that it needs one current amplifier for one control axis. We adopt this newly designed electromagnetic bearing system to the 6 D.O.F. linear motion table as a magnetic suspension([1,2,3]). The linear positioning of the table with a 100 mm stroke is driven by brushless DC Linear motors and the other 5 D.O.F. of the table are controlled by the digital controller with magnetic bearing actuators. The novel electromagnetic bearing system guarantees the high load capacity and it needs less current than conventional type of the electromagnetic bearing so that it gives low power consumption and elimination of problems caused by the heat generation.