Control System Design for a Five-Degree-of-Freedom Electrospindle Supported With AC Hybrid Magnetic Bearings

This study investigates a five-degree-of-freedom (5-DOF) electrospindle that is supported with ac hybrid magnetic bearings (HMBs). Compared with electrospindles supported with magnetically suspended dc magnetic bearings, an electrospindle supported with ac magnetic bearings is cost effective and efficient. Therefore, the application value of the latter to the project is higher than that of the former. An analysis from a previous work on the 5-DOF ac HMB-supported electrospindle had determined its insufficiencies. Based on this analysis, this study focuses on solving control problems in practical applications by designing a control system. The control system design includes the overall schematic, prototype, hardware, and software designs. Several performance tests have been conducted to verify the effectiveness of the proposed control system design. Results of the tests indicate that the rotor has excellent characteristics, such as good start-of-suspension performance, stable suspension characteristics with and without load, excellent antidisturbance characteristics, and faultless suspension characteristics within the supercritical speed range with an improved controller. Finally, subsequent measures for future research on the 5-DOF ac HMB-supported electrospindle are also provided.