Sensorless drive of surface mounted permanent-magnet brushless DC machines with diametric windings based on inductance measurements

Last decades, important progress have been made in sensorless control methods based on the tracking of magnetic anisotropies linked to the rotor. These methods allow to estimate the rotor position at low speed down to standstill. The magnetic anisotropy is generally approached by a sinusoidal shaped function. However, the theory must be adapted in case of additional harmonic content in the anisotropy function. This paper specifically addresses the problem for the surface-mounted permanent-magnet brushless DC machines with diametric windings. They present a peculiar magnetic anisotropy that suggests a simple method to detect the inversion of the magnetic field as a replacement to the dedicated sensors which are often used.