Fault Diagnosis and Fault-Tolerant Control of Bearingless Induction Motor Based on Wavelet Transform and Asymmetric Displacement Sensors

First, to handle the fault identification of displacement sensors for a bearingless induction motor (BIM), a fault diagnosis strategy based on wavelet transform and asymmetric displacement sensors is proposed. An initial diagnosis is made by analyzing the numerical relationship between the output values of asymmetric displacement sensors. Then, the final diagnosis is completed by combining the local maximum value of the output signal from the sensor after the wavelet transform. Second, to achieve the normal operation of the BIM after the failure of the displacement sensor, a fault-tolerant control system is established using an asymmetric structure and a coordinate transformation matrix. Different coordinate transformation matrices are selected according to the specific combinations of sensor faults. The simulation and experimental results demonstrate that the proposed fault diagnosis strategy can accurately identify six different combinations of faulty sensors. Furthermore, after a fault occurs, the fault-tolerant control system enables the motor to restore normal operation within 0.02 s, significantly improving the reliability and operational stability of the BIM.