Robust speed control of induction motors using adaptive observer

A nonlinear robust adaptive output feedback speed controller is designed for induction motors. The control uses only measurements of the rotor position and stator current and temperature. It contains two observers, a ninth-order adaptive observer to estimate the rotor flux and rotor resistance, and a third-order high-gain observer to estimate the rotor speed and acceleration from its position. The control is robust to uncertainties in the motor parameters and a bounded time-varying load torque. It guarantees that the speed tracking error can be made small by choice of certain design parameters. Experimental results are shown.