Speed Sensorless Control of Bearingless Induction Motors Based on Adaptive Flux Observer

To realize the speed self-identification of the suspension rotor in the low-cost operation control of a bearingless induction motor (BIM), a speed sensorless control strategy based on the adaptive flux observer is proposed. Firstly, the stability condition of the observer is analyzed by the small-signal linearization method, and the output errors of the observer in two stationary coordinate systems are transformed into the rotor magnetic field rotating coordinate, and condition of the error feedback matrix satisfying the observer stability is obtained. Secondly, based on the construction of the full-order model of the controlled object, a feedback loop containing the measured object and its variable is designed, and a reduced-order speed observer is constructed to realize the speed self-identification of the BIM. Finally, simulation and experimental verification research are carried out on the BIM speed sensorless vector control system. Both simulation and experiment results show that the proposed speed self-identification method can not only realize speed sensorless operation under no-load, speed change, an abrupt change of load effectively, but also make the motor has a good suspension performance.