Control System And Fault Diagnosis Of Brushless DC Motor For Electric Vehicle

Due to the continuous deterioration of the environment and the extremely limited fossil energy,our country has made great efforts to support the development of new energy vehicles,and the electric vehicle has developed rapidly with its lower price and cost.Brushless DC motor(Brushless Direct Current Motor,BLDCM)has advantages of AC motor which the structure is simple;reliable operation and convenient maintenance,as well as the advantages of DC motor which has high efficiency speed regulation characteristics.BLDCM has no mechanical commutation limit,which makes the system small,light weight.It has been widely used in recent years.It usually uses the control mode,which gets six rotor position signals in a power cycle for electronic commutation.Now the method is generally used by three Hall sensors which are installed in the shell of the generator(between 60 and 120 degrees)for detecting the rotor position.But those sensors are often affected by temperature,electromagnetic interference,dust and other environmental factors and can not work normally.Even serious damaged eventually leads to failure of the motor control system.If the above problems occur when driving a EV car,it may cause damage and threat to the passengers and surrounding people.Consequently,it is very important to improve the reliability of the motor control system.In this context,based on the existing BLDCM controller in the market,the controller integrated no-Hall and Hall control mode,finally developed the BLDCM controller with the fault diagnosis and fault tolerant control.First of all,after in-depth understanding of the brushless DC motor and its control principle,analyzing of the rotor position sensor and rotor position sensorless control method,a control plan of the power switch modulation under different working conditions was developed.The PI closed loop speed control system was designed for speed control because it has the characteristics of fast response and good real-time performance.The common causes of rotor position sensor faults,current faults and voltage faults are analyzed in detail.Secondly,after defining the function and performance requirements of Brushless DC motor controller for electric vehicle,the hardware circuit was designed and developed by AltiumDesigner.Based on the reliability and stability of the system,the cost of the controller was further reduced by using the idea of combining the integrated module with the discrete components.The hardware circuit was mainly composed of three parts: single chip microcomputer and its minimum circuit,power supply circuit,signal input/output circuit.And on the base of hardware,with the modularization oriented,KeilMDK was used to develop the software with C.Then the integration of sensor/sensorless control mode switch with automatic was achieved;the fault-tolerant rotor position sensor fault diagnosis and fault diagnosis of the voltage and current was completed;the motor stability and reliability was improved.Finally,according to the function and performance requirements of the designed controller,the 80BL103 motor test bench was built,and the software,hardware function as well as the reliability of BLDCM controller are tested.With the controller,BLDCM running smoothly,responsing fast.The experiment results showed that the designed of integration of sensor/sensorless control switching automaticly,the fault tolerant control based on rotor position sensor and the fault diagnosis of voltage as well as current were realized.