Smooth switching controllers for reliable induction motor drive operation after sensor failures

This paper presents a switching control method that can be actuated by a supervisory controller, with emphasis on smooth transitions between various open and closed loop controllers in real time. Through conversion of commands into non-periodic voltage values in the synchronous qd0 reference frame, hand-off transient reduction is achieved by controlling the rate of change of stator voltage commands during changeover. Through this method, smooth switched supervisory control can be achieved without synchronization or phase coordination between different commands from different controllers. Controllers are selected based on available sensor feedback. A system containing three controllers is simulated and tested with simulated sensor loss. Results of the proposed smooth switching controller compared to abrupt switching between control commands are compared. The proposed scheme is shown to reduce current and torque transients and maintain smooth operation of the drive. Given that multiple controllers and the switching logic are computationally intensive from an embedded system perspective, the proposed method is verified to operate in a processor-in-the-loop (PIL) environment on a Texas Instruments C2000 microcontroller.