A robust position sensorless vector control of permanent magnet machines by torque angle estimation

This paper presents a new position sensorless vector control algorithm for PM machines. The algorithm is based on estimating the torque angle, defined as the angle between the stator current and the rotor flux vectors. Controlling the torque angle will control the torque production and thus, the rotor speed of the machine without a position sensor. Robustness to parameter variations and performance characteristics of the algorithm have been discussed. Since the torque angle estimation requires no saliency of the rotor, this scheme works equally well for PM machines with both surface mounted and buried magnet rotor structures. Experimental results are presented to substantiate the theory. Advantages and limitations of this scheme are also summarized.