Sensorless vector control of PMSM using SMO and NLDO

In the proposed paper a state feedback controller is designed using Jacobian linearization of PMSM around an operating point which is adaptively refreshed using Non Linear Disturbance Observer (NLDO). This observer estimates load torque (which is considered as disturbance) using knowledge of speed and stator currents. The speed is normally measured using speed sensors like optical encoder. In this work, speed and rotor position are estimated using sliding mode observer (SMO). This estimated speed is given as an input to NLDO. Thus these two observers are cascaded in this scheme for sensorless vector control. Advantage of proposed cascaded scheme is that it replaces three PI controllers by state feedback controller. State feedback control gain can be mathematically determined using pole placement, thus avoiding complex procedure of tuning three PI controllers.