Multi-hybrid Active Magnetic Bearing Design for Milling Spindle Applications

Active magnetic bearings (AMBs) have been gradually developed and used in industrial applications. For a milling spindle system with full magnetic support, at least one axial AMB and two radial AMBs should be included. As a result, the milling spindle dimensions will probably be too large for the application of machine tools. A multi-hybrid AMB design, in which one axial AMB, one radial AMB, and a permanent magnet (PM) are combined, is reported in this work. The PM is embedded for axial suspension for the rotor weight so that the force requirement and the dimensions of the axial AMB can be reduced. On the other hand, magnetic channels were specially designed to couple the three magnetic loops generated by the AMBs and PM instead of isolating these magnetic fluxes individually. The proposed design is also suitable for applications of robot arm joints, such as waist and shoulder joints, to improve the bearing lifetime under heavy loads and to actively regulate the joint position deviation. The proposed multi-hybrid AMB design was practically manufactured after intensive analyses and verified by practical tests.