Adaptive backstepping design of an observer for the rotor speed and field of an induction motor

High performance operation of speed controlled AC drives without mechanical speed/position sensors rely on the dynamic models for estimation of flux and speed. Using backstepping, which is a recursive nonlinear design method, a new approach for the design of observers for speed sensorless control is developed. The resulting scheme leads to a nonlinear full order observer for the rotor field. The rotor speed and the stator resistance are estimated by adaptive backstepping. Assuming motor parameters known the design achieves stability with guaranteed region of attraction. The adaptive backstepping observer is used in a rotor field oriented controller and robustness due to variation of motor parameters is analysed by simulation.