Discrete time sliding modes observers for induction motors

An extension of the discrete-time sliding modes observer, developed by Takahashi and Peres (1996) for discrete-time systems subject to uncertain disturbances and varying or unknown parameters is presented in this paper. This extension allows the observation of systems with “non-matching” non-linearities. Such an observer is employed to estimate the flux and torque of the induction motor. Two formulations are presented: the first for rotor resistance disturbance rejection, the other for stator resistance disturbance rejection. These formulations allow the observer design even in the case of total lack of knowledge on some motor parameters. There is no need of a priori information on variation bounds, nominal values or statistics on the unknown parameter