Sensorless direct vector control of induction motor with a unified sliding mode observer

A unique solution to estimate of the rotor flux, the rotor speed and the rotor time constant, which are essential in speed sensorless direct and indirect vector control of induction motor is aimed. The measured stator currents and the voltages are used for proposed observer, in which all estimates are obtained from current estimation errors by using the sliding mode theory. In order to ensure the convergence in any operational conditions a nonlinear additional term is added to the flux observer structure. Full stability analysis based on the Lyapunov stability method is derived. The proposed algorithm employed for the direct type sensorless vector control drive system in this study. The effectiveness of the suggested observer is confirmed by the simulation results.