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 de-veloped. The resulting scheme leads to a nonlinear full order observer for the rotor field. The rotor speed and the stator resis-tance are estimated by adaptive backstepping. Assuming motor parameters known the design achieves stability with guaran-teed 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.