An improved method to estimate initial rotor position for surface-mounted permanent magnet synchronous motors

Permanent magnet synchronous motors (PMSM) are widely used in servo systems, and many methods have been proposed to solve the critical problem of detecting the rotor position in real time. However, existing methods are not suitable for the detection of initial rotor position for surface-mounted permanent magnet synchronous motors (SPMSM). A simple and highly accurate method utilizing an incremental encoder is presented. By applying certain current vectors, monitoring the direction of motor´s rotation, and changing the next applied current vectors, the initial rotor position can be obtained.