A new approach to sensorless vector control of SPMSM with adaptive sliding-mode observer

This paper presents a new approach to the sensorless vector control of Surface Permanent Magnet Synchronous Motor (SPMSM). It shows that the time-delay, in electrical rotor position estimation, does not influence the vector control when the d- and q-axis current components are accurately estimated. The PI controllers, fed by the actual d- and q-axis current errors, generate the correct voltage references in the estimated rotor reference frame. As a consequence, the coordinate transformation needs the estimated rotor position with no correction. To obtain accurate estimates of the d- and q-axis current components, it is sufficient that the estimated e.m.f. and current space vectors have the same delay as to the actual ones. An adaptive sliding-mode observer, with chattering-noise low-pass filter, is used to estimate the e.m.f. space vector, and a similar low-pass filter to delay the current space vector. The rotor speed and position are obtained from the estimated e.m.f. space vector and its derivative. Simulation results are presented to prove the effectiveness of the new approach to sensorless vector control.