Sensorless control of surface permanent magnet synchronous motor using a structural adaptive flux observer

Very few papers have been published on sensorless control of surface permanent magnet synchronous motor (SPMSM). The difficulty with nonsalient rotor is the equal inductances along both d and q axes. In this paper, a new approach to sensorless speed control and initial rotor position estimation for a SPMSM drive is presented. At a rotating condition, speed and rotor position estimation of SPMSM drive is obtained through an observer with compensation by only measuring phase voltages and currents. The initial rotor position is performed by using the nonlinear magnetization characteristics of the stator core caused by the rotor magnets. Experimental results show that in both steady and transient state, the system can achieve expected performances.