Levitation forces control by current vector orientation for a bearingless motor with hybrid rotor structure

Because levitation forces in x-and y-direction for a bearingless motor with hybrid rotor structure are coupled, the decoupling method is needed to independently control the forces. This paper presents levitation forces control strategy through current vector orientation. By using transformation of two sets of winding phase currents in x-y frame to new variables in a d-q rotating reference frame, the levitation forces can simply be expressed by the new variables. Then estimating spatial rotating angle in torque winding current vector and locking d-axis in d-q rotating reference frame on the current vector, decoupled control of levitation forces can be obtained through current vector control in levitation forces winding. Finally, a practical control system of levitation forces for a bearingless motor with hybrid rotor structure based on DSP TMS320C32 and Xilinx CPLD has been completed and the tested results show that the proposed control strategy is feasible.