Research of position sensorless control for PMSM based on sliding mode observer

In the Permanent Magnet Synchronous Motor(PMSM) field-oriented control system, the information of rotor position and speed are necessary in order to achieve high performance. This method is based on sliding mode observer theory using Lyapunov stability criteria. The proposed estimation method is implemented using a stator flux/current and a modified back Electromotive Force(EMF) observer connected in cascade. The flux/current observer based on sliding mode techniques ensures stator currents convergence while the modified back EMF observer provides accurate rotor position estimation at a wide range of motor speeds. Also the variations of the parameters, such as resistance and inductance variations are analyzed. Simulative results show that the observer is robust to parameter variation and able to observe the position of rotor so as to achieve sensorless vector control of PMSM.