An Enhanced Linear ADRC Strategy for a Bearingless Induction Motor

To provide faster speed response, better current characteristics, more stable suspension, and stronger disturbance immunity for a bearingless induction motor (BIM) system, an enhanced linear active disturbance rejection control (ELADRC) strategy is proposed. First, based on the air-gap flux-oriented control, the speed LADRC and the suspension LADRC are, respectively, designed for the torque winding and suspension winding. The uncertainties and disturbance of the system are treated as a total disturbance in LADRC and linear extended state observer (LESO) is used to observe and compensate for it in real time. Second, by analyzing the defects of LADRC, the speed ELADRC and the suspension ELADRC with cascaded LESO are designed based on LADRC to improve the stability and disturbance immunity. Third, the stability and the tracking performance of the second-order ELADRC are analyzed. Finally, simulation and experimental comparisons of the PID control strategy, the LADRC strategy, and the ELADRC strategy are carried out. The analysis and results show that the proposed strategy not merely has good speed response and current characteristics and lowers the influence of load disturbance, but also realizes the fast and stable suspension of the rotor and improves the anti-disturbance performance of the suspension system.