High Reliable Near-Zero Speed Control for Sinusoidal PMSM Drives with Low Resolution Position Sensors

In this paper a back-EMF-based method is used in conjunction with three very low-cost integrated circuits based on the Hall-effect to estimate the rotor position of direct-drive PMSMs to be used for traction purpose of an electric wheelchair. A speed estimator based on rotor frame machine model (SERF) has been implemented for the PMSM drives, and then the rotor position estimation is achieved by means of a discrete integration of the estimated speed. The three Hall effect sensors are used to detect the rotor initial position as well to reset the error on the rotor position estimation every 60 electrical degrees. Start-up and near-zero speed operations for the drive, equipped with the speed estimation algorithm, have been investigated by means of simulations and an extensive experimental test campaign