A novel method for PM synchronous machine rotor position detection

The paper presents a new efficient method for the detection of rotor initial position of a permanent magnet synchronous motor with an incremental encoder, including the case of a loaded motor. The fundamental principle of this technique is to determine the rotor position at startup by estimating the electrical angle which allows passing the motor rated/peak current through stator windings without moving the rotor from its standstill position. As compared to other approaches, the present technique does not cause motor rotation during rotor position detection and it is therefore very promising for particular kinds of applications, which do not allow the motor to rotate/move potentially in the wrong direction during startup. This method is more efficient in respect of accuracy and reliability than the conventional method using commutation signal, especially for small drives. Experimental results show that the proposed algorithm is capable of reliable and fast rotor initial position estimation.