Active Disturbance Rejection Control for Bearingless Induction Motor Based on Hyperbolic Tangent Tracking Differentiator

To meet the operation requirements of a bearingless induction motor (BIM) control system, such as fast speed response, stable suspension, and high disturbance rejection ability, an active disturbance rejection control (ADRC) strategy based on hyperbolic tangent tracking differentiator (HTTD) is proposed. First, based on the air-gap magnetic field decoupling control of the BIM, the uncertainties of the system itself and the load disturbance are regarded as a total disturbance. The extended state observer (ESO) is used to observe the total disturbance in real time. The speed ADRC and suspension ADRC are designed for the torque winding and suspension winding, respectively. Second, the hyperbolic tangent function is applied to the tracking differentiator (TD) of ADRC to simplify its structure. The frequency characteristic curves are analyzed through the sweep-frequency test, and the design parameters are further determined. Finally, this strategy is analyzed with simulation in MATLAB/Simulink and verified on an experimental prototype. Both simulation and experimental results show that the strategy not only has good speed and current characteristics but also reduces the effect of load disturbance on the system and improves the suspension characteristics of the BIM.