For salient-pole permanent magnet synchronous motor (PMSM), the amplitude of extended back electromotive force (EEMF) is determined by rotor speed, stator current and its derivative value. Theoretically, even at extremely low speed, the back EEMF can be detected if the current in q-axis is changing. However, it is difficult to detect the EEMF precisely due to the current at low speed. In this paper, novel full-order multi-input and multi-output discrete-time sliding mode observer (SMO) is built to detect the rotor position. With the proposed rotor position estimation technique, the motor can start up from standstill and reverse between positive and negative directions without a position sensor. The proposed method was evaluated by experiment.

Using magnetic flux barriers in the stator yoke of electric machines with fractional slots, tooth-concentrated winding, it is possible to reduce or even to cancel some space harmonics of low-order in the air-gap flux density resulting in lower rotor losses induced by the armature reaction field. A novel interior permanent magnet synchronous machine (IPMSM) is designed using this new technique [1]. In this paper losses of this new machine are analyzed and compared with conventional 12-teeth/10-poles concentrated windings IPMSMs. With this new design, losses of this IPMSM resulting from high-frequency (HF) injection for sensorless control are reduced compared with the conventional ones.