This paper describes a fault-tolerant controller (FTC) of induction motor (IM) with inter-turn short circuit in stator phase winding. The fault-tolerant controller is based on the indirect rotor field oriented control (IRFOC) and an observer to estimate the motor states, the amount of turns involved in short circuit and the current in the short circuit. The proposed fault controller switches between the control of the two components of measured stator current in the synchronously rotating reference frame and the control of the two components of estimated current in the case of faulty condition when the estimated current in the short circuit is not destructive of motor winding. This technique is used to eliminate the speed and the rotor flux harmonics and to assure the decoupling between the rotor flux and torque controls. The results of the simulation for controlling the speed and rotor flux of the IM demonstrate the applicability of the proposed FTC.

In this paper, we propose a robust nonlinear control design concept based on a coefficient diagram method and backstepping control, combined with a nonlinear observer for the magnetic levitation system to achieve precise position control in the existence of external disturbance, parameters mismatch with considerable variations and sensor noise in the case, where the full system states are supposed to be unavailable. The observer converges exponentially and leads to good estimate as well as a good track of the steel ball position with the reference trajectory. A simulation results are provided to show the excellent performance of the designed controller.