Closed-loop control method and system of suspension force of brushless direct current motor without bearing

The invention relates to a closed-loop control method of suspension force of a brushless direct current motor without a bearing, which comprises the following steps that displacements of a rotor on an x axis and a y axis are detected, the displacements are compared with given displacements, then displacement deviations from the x axis and the y axis are obtained, and given control suspension forces of the x axis and the y axis are generated; the current suspension forces of the x axis and the y axis are calculated in accordance with a control winding flux linkage of the suspension force, a phase angle and structure parameters of the motor, the current suspension forces are compared with the given control suspension force of the x axis and the y axis, and then the difference of the suspension force is obtained; according to the difference of the suspension force, a rotating angle of the rotor, a phase angle of the control winding flux linkage of the suspension force, a torque winding air gap flux linkage and t