The Research On Fault Tolerant Control Of Brushless DC Motor Under Sensor Failure

Brushless DC motor has advantages of light weight,high efficiency and good speed performance,which has been extensively used in electric vehicles,aerospace and robotics.However,when the brushless DC motor operates in a harsh environment,hall sensor is prone to failure.Once failure occurs,the torque ripple and current of the motor will be very large,which will destroy BLDC and its driving equipment,and in serious cases,it may endanger life and property.In order to ensure the reliable and safe operation of the motor,it is of important meaning to study the fault diagnosis of sensors and fault tolerance control of brushless DC motor.Firstly,the paper introduces the operating principle of brushless DC motor,and establishes the mathematical model of the motor in various coordinate systems,analyzes the vector control method of the motor and SVPWM modulation method.Through the simulation analysis,the difference between the vector control and the square wave control in the aspects of speed,current,torque are compared,and it is concluded that the vector control is better for the motor,so the vector control is determined as the basic model of the motor fault tolerant control.Secondly,this paper proposes a fault diagnosis strategy based on hall combining jump edge and hall state value through combining various types of fault characteristics of hall sensor.Then,based on the fault characteristics,the improved zero order compensation and first order Taylor compensation are used for fault tolerance control.Through simulation model of fault tolerant control,analysis the changes of motor speed,current and torque during the fault period.Then verified the effectiveness of fault diagnosis strategy.Finally,the simulation test of fault tolerant control for the first order Taylor compensation method is carried out,the simulation results show that the parameters of the motor return to normal and the dynamic characteristics are good after the fault tolerant control is completed.The fault tolerant control method of sensorless technology is adopted when all hall sensors faults.Based on the second-order observer,the Luenberger full-order observer is constructed.There is a certain error using the inverse tangent function to estimate the position and velocity,so a more accurate method of normalized PLL is presented.Through building a sensorless control simulation model,different observers,arctangentand PLL are compared in the aspects of estimating speed and position.It is concluded that the method of using Luenberger full-order observer and PLL to estimate the position and speed is more accurate.Finally,the control system of Brushless DC motor is designed,including the design of hardware and software.The effectiveness of the proposed algorithm is verified by experimental analysis of the waveform control and vector control,hall sensor fault diagnosis and sensorless control strategy.