Radial Displacement Detection Using Sensing Coils Weakly Coupled With Magnetic Bearing

This article presents a novel displacement detection method with sensing coils weakly coupled with a conventional eight-pole active magnetic bearing. To improve integration, the sensing coils are completely wound on the magnetic poles of the active magnetic bearing. The proposed method is different from others since each sensing coil is wound around two teeth of an active magnetic bearing, reducing the mutual inductance coefficient between sensing and excitation coils. Thus, the influence of excitation coils on displacement detection can be reduced. A core multiplexing and frequency discrimination method is proposed to detect displacements along
${x}$
- and
${y}$
-directions, simultaneously. Experiment results show that sensitivity along the
${x}$
- and
${y}$
-axes are 8.98 and 5.61 mV/
$\mu \text{m}$
, respectively, showing the feasibility of displacement detection without being affected by displacement variation of the orthogonal axis. Finally, the displacement detected by sensing coils is used for close loop control in an active magnetic bearing system at 2500 rpm, validating the feasibility of sensing coils in active magnetic bearing control.