Research On Speed Sensor Fault-tolerant Control Of Asynchronous Motor

Asynchronous motor is widely used for its simple structure,low price and reliable operation,the motor vector control system makes asynchronous motor achieve the comparable performance with regard to DC motor,which expands its application.However,due to the influence of the working environment or improper operation,the motor control system may fail during operation.The speed loop is one of the important control loops in the asynchronous motor vector control system,where the speed feedback information comes from the measure value of speed sensor.When the speed sensor breaks down,the measurement of speed information is inaccurate or of fault state,which results in the instability of the system operation and even cause the control system to stop operating.Therefore,a speed estimation method and fault-tolerant control in the whole speed range is proposed in this paper to deal with the speed sensor fault of asynchronous motor.Firstly,the mathematical model of asynchronous motor in three-phase stationary coordinate system,coordinate transformation principle and vector control principle are analyzed.Secondly,the speed estimation principles of full-order flux observer,extended Kalman filter and high-frequency injection method are given,and the performance of three speed estimators is analyzed at low speed,medium speed,and high speed.The results show that the speed estimation performance of high-frequency injection method and extended Kalman filter is better than that of full-order flux observer at the low speed range,and the speed estimation using extended Kalman filter and full-order flux observer is better than that of high-frequency injection method at the medium and high speed range.Finally,the fault diagnosis method based on model and fault tolerant control method based on Euler voting algorithm are designed for speed sensor broken fault and fixed deviation fault.The absolute value of the residual error between the measured value of speed sensor and the estimated value of speed using different methods is compared with the set threshold value.When the speed sensor breaks down,the Euler voting algorithm is used to select the best speed estimator in the corresponding speed range as the speed feedback.Two kinds of speed sensor failures are simulated in MATLAB/Simulink,and the analysis of the results shows that no matter what kind of failure occurs in the speed sensor,the system can smoothly switch to the speed sensorless mode.In order to verify the feasibility of the method designed in this paper under the experimental conditions,the method is verified on the 3KW three-phase asynchronous motor experimental platform based on TMS320F28335.The experimental results show that the control system can maintain stable operation under the condition of speed sensor failure.