Application of Sliding Switching Functions in Backstepping Based Speed Observer of Induction Machine

This paper presents an analysis of the speed observer, which is based on the backstepping and sliding mode approach. The speed observer structure is based on the extended mathematical model of an induction machine. The observer structure is based on the measured phase stator currents and transformed to (alpha beta) coordinate system. The stator voltage vector components are treated as known values. Additionally, such an observer structure is extended to the integrators. The observer stabilizing functions contain the appropriate sliding surfaces, which result from Lyapunov function. The rotor angular speed is obtained from nonadaptive dependence. Stability analysis of the observer structure based on Lyapunov theory is presented in order to guarantee the estimation errors decay to zero. In the sensorless control system, the classical sliding-mode controllers are applied with the multiscalar variables transformation. The theoretical derivations are verified in experimental waveforms.