Backstepping fault tolerant control based on second order sliding mode observer: Application to induction motors

In this paper, a fault tolerant control for induction motors based on backstepping strategy is designed. The proposed approach permits to compensate both the rotor resistance variations and the load torque disturbance. Moreover, to avoid the use of speed and flux sensors, a second order sliding mode observer is used to estimate the flux and the speed. The used observer converges in a finite time and permits to give a good estimate of flux and speed even in presence of rotor resistance variations and load torque disturbance. The stability of the closed loop system (controller + observer) is shown in two steps. First, the boundedness of the trajectories before the convergence of the observer is proved. Second, the trajectories convergence is proved after the convergence of the observer. The simulation results show the efficiency of the proposed control scheme.