A sliding mode position controller for induction machines with diametrical inversion of stator voltage

The diametrical inversion of stator voltage is used to control the rotor shaft position of an induction motor. The method substitutes the actual spatial voltage phasor applied to the motor, by another voltage phasor, which is diametrically opposed to the first and rotates in inverse direction. This substitution is made at high frequency (congruent to 11 kHz). The resulting three phase voltage sequences applied to the machine are PWM generated by a sliding mode controlled voltage inverter, reading only the voltage applied to the motor. A first order sliding mode switching law (reading the shaft position and its speed) is used to decide which phasor is applied. The proposed method does not need the knowledge of the machine model or parameters. Some simulations results exhibit the system robustness to external torque disturbance. The electromagnetic torque response is fast (congruent to 5 ms). Simulations and experimental results are shown and discussed.