Shaft speed, load torque and rotor flux estimation of induction motor drive using an extended Luenberger observer

A high-performance induction motor drive needs the signals of shaft speed and rotor flux. Flux signals are approached commonly in a way of calculation while the speed is mostly obtained by direct measurement. In some cases, however, the elimination of speed sensors is quite necessary as they tend to reduce system reliability when working in hostile environments. The authors describe the use of an extended Luenberger observer (ELO) for this application, because the extended Kalman filter (EKF) may not be good enough for producing estimates which are fast enough to trace target transients. In this paper two ELOs which not only can estimate motor speed but also load torque and rotor flux are designed. Experimental results for a full-order ELO and an EKF are given. It evidently proves that the ELO behaves much better than the EKF in this practical experimental conditions