Sensorless direct torque control of a permanent magnet brushless AC drive via an extended Kalman filter

The performance of an extended Kalman filter (EKF) based sensorless direct torque control technique for a PM brushless AC drive is described and compared with that which is obtained with other sensorless methods for estimating the rotor speed and position from the stator flux-linkage. It is shown that, since the EKF inherently has adaptive filtering capability and does not introduce a phase delay, the technique provides better speed and position estimation.