Research On Fault-tolerant Control Of Position Sensor In BLDC Drive System Of Electric Vehicle

Brushless DC motor(brushless DC motor,BLDC)has the advantages of better power density and high efficiency,and is often used as a drive motor for electric vehicles.When the BLDC runs in a complex and harsh working environment,the position sensor is easy to be faulty,and causing problems such as abnormal current of the motor,high torque ripple and out of control of speed regulation,and even endangers the safety of drivers.Therefore,in order to enhance the reliability of the safe operation of electric vehicles,the paper conducts a very detailed research on the fault-tolerant control algorithm.The work content is as follows:Firstly,the paper explained the basic structure and working method of BLDC in detail,and establishes the mathematical model.Based on the features of position sensor fault signals,the faults are divided into five types,and the BLDC servo control system model with faults is established.Finally,the validity of the fault model is verified by Simulink.The simulation results show that both single-phase and multi-phase sensor failures will affect the speed regulation performance of the motor.The fault model of the BLDC servo control system also is the basis of the subsequent fault diagnosis and fault-tolerant control research of the position sensor.Secondly,the improved adaptive sliding mode observer is used for fault diagnosis of the position sensor to solve the jitter problem of the traditional sliding mode observer.The piecewise function is used to replace the traditional switching function,the power reaching law is used to enhance the performance of the observer,and the resistance and inductance parameters estimated online are used for the adaptive adjustment of the gain matrix of the sliding mode observer.Finally,the methods based on the rotational speed residual and phase difference analysis were used to diagnose the fault.Through the simulation results,it is found that the method adopted in this paper can not only effectively weaken the chattering of the estimated value obtained by the observer,but also make the fault diagnosis method more accurate.Then,the fault-tolerant control method of the position sensor is studied to enhance the reliability and stability of the motor drive system.When only one sensor fails,take the normal signals of the other two phases as a reference,and use the time interval replacement method for fault tolerance;For a two-phase or three-phase position sensor failure,the method of rebuilding the Hall signal based on the detection of the zero-crossing point of the line back EMF is used.The simulation results show that the motor can basically operate normally,which verifies that the fault-tolerant control algorithm proposed in the article is not only effective but also feasible.Finally,an experimental platform for the BLDC fault-tolerant control system is built.On the basis of hardware design and fault-tolerant algorithm design,the methods proposed in this paper are applied to the experimental platform.Through the analysis of experimental results,the method accuracy and practicability of the method described in this paper are proved,which provides support for engineering practice in this research field.