Rotor position control for induction machines using diametrical inversion of stator voltage

To accurately solve the speed or rotor position control problem of an induction motor (IM), the key has been a proper design of a torque controller included in a cascaded control structure. The IM dynamic behaviour presents a nonlinear coupling between the flux and the torque and so the decoupling has been the first task, as in field-oriented control and direct torque control, where some feedback signals are obtained using observers. An IM command action, the diametrical inversion, whose implementation is easy and gives good results, uses the sliding mode. A mechanical first order switching function determines the successive application of IM stator voltage diametrical inversions. A torque controller is not needed, the sliding mode robustness eliminates the decoupling problem, and the fast inversion of the electromagnetic torque allows a rotor positioning faster than a torque controlled second order system. Some simulation and experimental results show the position responses and exhibit the system robustness to external disturbances and winding resistance variations with temperature