“…in which i d , i q are the direct axis and quadrature axis currents respectively, R s , L s are the resistance and inductance of stator respectively, f is the permanent magnet flux linkage, p is the number of pole pairs, m is the angular speed of the rotor, J m is the moment of inertia of the rotor, K t is the torque constant, B m is the viscous friction, T l is the unknown load torque, u sd , u sq are control voltages in dq-frame. The values of these parameters are given in Table I, which are the same as the ones in [26], where I max is the maximum current, F pwm is the value of the PWM frequency and T s is the control period. In the actual system, the stator resistance, inductance, salient-pole effect and flux linkage are all time-varying in intervals.…”