Design of a PCB integrated eddy current sensor with shield feature for radial rotor displacement measurement

Active magnetic bearings require position feedback to enable a stable control of a levitating rotor. The position information can be provided by explicit position sensors or the usage of self-sensing bearing topologies. In this study an investigation of a PCB integrated eddy current sensor for radial rotor displacement measurement is conducted. In many AMB applications a short rotor length is desired to handle flexible rotor characteristics at high rotational speeds. Therefore, the active magnetic bearings, the motor as well as the sensors shall obtain a small axial length. Conventional eddy current displacement sensors often obtain a cylindrical shape with a circular measurement spot on the rotor target material, which defines the minimum axial length of the sensor arrangement. The aim of this study is to design a low-cost PCB integrated eddy current sensor with an arc-shaped measurement spot and low axial dimension. In contrast to previous studies in this field, it is investigated if it is possible to achieve a feasible sensor design without the use of a coupled coil arrangement of excitation and sense coils. This study covers the sensor design, measurements on a prototype as well as a performance comparison between a non-shielded and a shielded sensor design.