High precision observer of an induction motor with variable structure control

This paper presents a new observer for an induction motor, the nonlinear time-variant multivariable system. The method uses only the stator current to observe simultaneously the speed and the rotor current. The law of Lyapunov-stability underlies the observer. During the design, a variable structure term is introduced to counteract the uncertain terms, which leads the condition of Lyapunov-stability is satisfied. Consequently the good properties of the observer, such as the strictly asymptotical convergence, high precision and the robustness against the parameter variation, are ensured by the theoretical analysis. The simulations show the feasibility and the good performance of the observer