Low-Cost PCB Integrated Inductive Sensor 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 techniques. This study deals with a PCB integrated inductive sensor design for radial rotor displacement measurement. The sensor design consists of a six-pole stator arrangement, a soft magnetic rotor ring as measurement target as well as a PCB integrated coil configuration. The sensor principle is based on the detection of inductance deviations of an eccentrical levitating rotor. The surrounding stator poles of the sensor enable a large and distributed measurement area which allows a suppression of imperfections on the rotor surface. Concerning design optimization, a short axial sensor length is aspired to enable a less construction space consuming sensor integration compared to conventional inductive sensor designs. Thus, a smaller sensor enables the possibility of shorter rotor shaft designs to overcome challenges of flexible rotor characteristics or inadmissible axial thermal expansion. This study covers an introduction to the sensor’s working principle, design considerations as well as an experimental verification of a PCB integrated inductive sensor prototype.