Research And Control For Sensorless PM Brushless DC Motors

Permanent magnet brushless DC motor has advantages of high efficiency, large torque, small volume and other advantages, together with the rapid development of high performance micro processor and logic circuit, which both make its application develop rapidly and unprecedentedly in social production and social life. Compared with the traditional sensor permanent magnet brushless DC motors, the performance and application of the Brushless Permanent Magnet DC motors(BLDCM) are further expanded.This paper analyzes some common position sensorless control methods and especially makes study on back EMF method, meanwhile this paper analyzes the suppression of the torque ripple during non-commutation when motor in low speed. Then, this paper analyzes the motor by using special motor driver chip and powerful motor control platform. The main purpose of this paper is to study the BLDCM which is been create in new, and this motor will be used in the electric power steering and the condensation part. Binding the working condition and the characteristic of this motor, this paper will focus on the starting link and the link of the operation of the motor in order to achieve the normal operation of the fast starting and stable without jitter.First, this paper analyzes the working principles of PM BLDCM and establishes mathematical model under ideal conditions, based on which the MATLAB/Simulink is adopted to do simulation analysis of the back-EMF method. Regards with the back EMF method, this paper mainly analyzes the zero-crossing algorithm adopted simulation of neutral point Meanwhile this paper analyses and studies the suppression of the torque ripple during non-commutation when motor is running.After getting the desired results on simulation analysis, a special sensorless permanent magnet brushless DC motor driver chip is adopted to do the test, the paper has designed the hardware circuit of control system to do the simulation testing analysis, mainly for the analysis of specific control effect in practical application of the back-EMF method.Finally, in order to do further analysis on the impact of back-EMF method for the motor and torque ripple reduction, this paper uses the dsPIC32J204 control chip produced by Microchip as a software test platform to make a further analysis on the back-EMF method and non commutation torque ripple and a series of experimental data and waveforms are obtained.The test uses two motors made by different manufacturers, adopting the two testing methods above, and both of them achieve expected objectives. The testing results show that the designed control system can be operated effectively and stably.