Research And Design Of Position Sensorless Control System For Six Phase Brushless DC Motor Based On DSP

Compared with conventional DC motors,the brushless DC motors remove brushes and commutation components and complete commutation function by power electronic devices which commonly use three-phase full-bridge inverter.The three-phase full-bridge inverter can eliminate the traditional DC motor in the commutation process energy consumption and equipment consumption.Due to its simple structure,large output torque,wide range of speed regulation,high working efficiency,reliable operation and low electromagnetic noise,the motor is widely used in the areas of national production,home appliance,defense,aerospace and new energy vehicles.However,at present,most of the applications are to install the position sensor on the motor,and the position sensor can not accurately measure the position of the rotor under the circumstance of harsh environment or prolonged operation,which affects the normal starting and commutation of the motor.In this context,a control method of BLDC sensorless position sensor is proposed.In this paper,six-phase brushless DC motor is as the research object.Firstly,the basic structure of six-phase brushless DC motor and its basic working principle are introduced in detail.By comparing a variety of working methods,selecte four or four conduction mode and the research on the continuous flow of non-conducting phase under different modulation modes is also studied.The last method is the PWM_ON_PWM modulation method.Through the research and analysis,a novel three-stage starting method is proposed for the starting of a sensorless six-phase brushless DC motor position sensor.The commutation part adopts the method of line back EMF combined with the back-EMF differential detection.Secondly,in view of the proposed control system of six-phase brushless DC motor without position sensor,analyzes the principle and mathematical model.The simulation model of six-phase brushless motor and the control system of sensorless control system are built by using PLECS simulation software.The simulation platform verifies the feasibility of the new three-stage starting method proposed in this paper and the feasibility and accuracy of commutation signal detection by line back EMF method and line back EMF difference method during the single winding mode operation are verified.In addition,the feasibility and accuracy of the motor commutation signals are jointly determined by the UVW and RST six-line back-EMF zero-crossing signals when the motor is operating in dual-winding mode.Finally,the experimental platform is set up and the hardware circuit and DSP software program of the sensorless control system for six-phase brushless DC motor are designed.Then through the motor start-up,acceleration and deceleration operation test,combined with the oscilloscope observation line back EMF and the back-EMF differential zero-crossing signal,the phase current signal,the drive signal.By analyzing the waveforms of various signals obtained from experiments,the feasibility and practicability of this design scheme are verified.