A robust nonlinear Luenberger observer for the sensorless control of SM-PMSM: Rotor position and magnets flux estimation

For a Surface-Mounted Permanent Magnet Synchronous Motor (SM-PMSM) with currents and voltages as only measurements, we propose a robust nonlinear Luenberger observer estimating both the rotor position and the magnets flux. The robustness of the observer to the mechanical load connected to the machine shaft comes from an appropriate choice of coordinates, while its robustness to the physical parameters of the machine is studied and reveals satisfactory results. We prove that observers may be designed, i.e. the system is said to be observable, under the only assumption that the rotor speed is non-zero. Experimental results assess its validity.