Analytical design and experiment of radial inductive displacement sensor with full-bridge structure for magnetic bearings.

In magnetic bearing systems, the air gap between the stator and the rotor is generally measured with an eddy current displacement sensor. However, the inductive displacement sensor (IDS) is a preferred choice due to its structural consistency with magnetic bearings, which contributes to a compact system design. While most of the reported IDS research studies are based on three-dimensional finite element method (3D FEM) simulation and the IDS of such studies is designed with a half-bridge structure, in this paper, a higher sensitivity IDS with a full-bridge structure is proposed. To optimize the response of the sensor, an accurate theoretical analysis method is presented for the sensor based on the Schwarz-Christoffel transformation, which is used for compensating fringe effects of sensor inductance. Compared to traditional 3D FEM simulation, fast sensor design and optimization can be achieved with the proposed method. Experimental results agree well with theoretical predictions. The sensitivity of the proposed sensor is nearly 15.5 mV/μm, and the displacement resolution is better than 1 µm.