High performance PMSM drives without rotational position sensors using reduced order observer

A new position sensor elimination method for high performance permanent magnet synchronous motor (PMSM) drives is presented in this paper. The back-EMF quantity of the PMSM has mechanical information such as the rotor speed and angle in itself. Therefore, without exterior rotational sensors or other mechanical data which include machine inertia, viscous friction, and outer load condition, these essential information for proper PMSM drives can be obtained successfully from only the back-EMF quantity. In this study, with the help of the modern state observer technique for back-EMF estimation, the rotor position as well as the machine speed are estimated strictly and utilized for practical sensorless PMSM drives. Furthermore, introducing the `angle ambiguity compensation´ algorithm, the proposed sensorless scheme has good starting ability and high performance driving characteristics even in the transient state, such as speed fluctuation or speed reversal. In order to verify the feasibility of the proposed method, extensive experimental results are presented under full operating conditions, 150~2500 [RPM] speed and 0~1 [p.u.] load range