Compared with the traditional DTC, the EKF estimator can
deal with the error which is from the stator resistance, because
only the function f(x,u) contains the stator resistance Rs. When
the stator resistance Rs changes, the EKF estimator can correct
the error of the model by the closed-loop structure to improve
the performance of the system, as it is shown in Fig. 6. When
the actual value of the stator resistance changes, the estimated
speed can track the actual speed fast, and the estimated stator
linkage and the torque value is equal to the actual value. The
EKF estimator boasts a small ripple of the flux linkage and the
torque.