Speed Sensor Fault Tolerant PMSM Machines: From Position-Sensorless to Sensorless Control

New sensorless observers (i.e., from stator currents/voltages measurements only), to be included into a simple observer-based sensorless control for the tracking of non-definitely zero speed references in nonsalient-pole surface permanent magnet synchronous machines (PMSMs), are proposed. They are obtained through a 'minimum distance' modification from recently presented position-sensorless observers (i.e., from rotor speed and stator currents/voltages measurements only). The rotor speed estimate is here directly provided by the phase locked loop (PLL)-based third-order steady-state linear kalman filter (SSLKF) that has been previously used to mitigate the distortions on the estimated position. Experimental results illustrate the effectiveness of the proposed approach in a speed sensor fault-tolerant scenario.