Digital control system design for bearingless permanent magnet synchronous motors

This study investigates a digital control system which is used in bearingless permanent magnet synchronous motors (BPMSMs). Compared with traditional permanent magnet synchronous motors, a BPMSM is characterized by higher speed and no mechanic friction. Therefore, the application value of the latter to the special area is higher than that of the former. An analysis from previous work on the BPMSM had proved its feasibility, and some performances such as suspension force, inductance and so on were also investigated. Based on this analysis, this study focuses on solving control problems in practical applications by designing a control system. The control system design includes overall schematic, hardware and software designs. Main software systems, including the force/current transform module and closed loop control module for radial displacement, are analyzed. Interface circuit for radial displacement, current feedback circuit and dead zone protection circuit are designed for the hardware system. Finally, several performance experiments have been conducted to verify the effectiveness of the designed digital control system. Experiment results indicate that the rotor has unique characteristics, such as stable suspension performance, good start-of-suspension performance, and rapid anti-disturbance features