Inductance-based position self-sensing of a brushless DC-machine using high-frequency signal injection

Inductance-based self-sensing methods allow to estimate the rotor position by tracking the magnetic anisotropy linked to the rotor. The inductance can be quickly estimated by measuring the response on the injection of high-frequency signals in addition to the signals of normal-operating control. Compared to more conventional permanent-magnet synchronous machines, driving a low-inductance brushless DC-machine presents some issues that must be taken into account: significant inverter nonlinearities, impact of the stator resistance on the inductance estimation, important harmonic content in the magnetic field that leads to errors in the rotor-position estimation. In this paper, we propose a signal-injection solution that removes the stator-resistance impact. A solution to the inverter nonlinearities is also discussed. Experimental results demonstrate the robustness of the control scheme at low and higher speeds.