Self-sensing for active magnetic bearings: overview and status

Self–sensing approaches permit active magnetic bearings to dispense with the usual position sensor and, instead, extract rotor position information from the voltage and current histories for the actuator coils. Mirroring the development of back–emf sensing of angular position in brushless DC motors, this technology has been a long time coming (more than 15 years) but has begun to be applied to commercial products. This review paper describes the process by which this emergence has occured and outlines some interesting problems that remain to be solved.