The authors propose a robust nonlinear controller based on a block control linearization technique combined with a second order sliding mode super-twisting algorithm for controlling the rotor speed of single-phase induction motors. The block control approach is used to design a sliding manifold in terms of the stator current and its desired value. The super-twisting sliding mode algorithm is applied then to render the designed manifold be attractive. A nonlinear observer is designed to estimate the unmeasured variables (rotor flux linkages and torque load). Copyright © 2012 John Wiley & Sons, Ltd.