Sensorless control of surface permanent-magnet motor based on model reference adaptive system

This paper describes a new method of rotor position and speed estimation of a surface permanent-magnet synchronous motor based on a model reference adaptive system (MRAS). The proposed method features the MRAS in a current control loop to estimate a rotor position and speed only with current sensors. A transient response of the estimated rotor position and speed in the MRAS determines transient behavior of the sensorless control. For this reason, the important point is to investigate a relationship between an actual and the estimated rotor speed. First, this paper proposes a structure of the sensorless control applied in the current control loop. Next, it proves the stability of the proposed method using hyperstability theory, and presents an optimal method of adjusting the transient behavior of the estimated rotor speed to that of the actual rotor speed with nonlinear compensation. Finally, several experimental results show the performance of the proposed method.