Displacement estimation method of bearing-free synchronous reluctance motor, method and device for controlling displacement-free sensor

The invention relates to a displacement estimation method of a bearing-free synchronous reluctance motor, comprising the following steps: constructing a band-pass filter BPF: sending coordinate- transformed suspension winding three-phase detection current into the band-pass filter BPF; extracting suspension winding high frequency induction current ix_i and iy_i through the BPF; then constructing a multiplication demodulator: taking the ix_i and iy_i as a first input signal of the multiplication demodulator; constructing a phase shifter, taking pulsation high-frequency voltage signal ud_i having gone through phase shift as a second input signal of the multiplication demodulator; obtaining I' and I signal after demodulation computation is carried out on the two input signals by the multiplication demodulator; then filtering high-frequency component of the I' and I' signal by a low-pass filter LPF, finally obtaining current components comprising rator radial displacement; afterwards multiplying corresponding sca