Research On Sensorless Brushless DC Motor Control Technology

With the development of power electronics and microelectronics technology, electroniccommutator is gradually replaced the mechanical commutator in Brushless DC Motor. So thatthe Brushless DC Motor not only has the speed performance of DC motor, but also overcomemany shortcomings of the external position sensor, volume becomes smaller, reliabilitybecomes better and efficiency becomes higher. Therefore, sensorless brushless DC motorcontrol technology has important significance and practical value.This paper mainly researches on sensorless brushless DC motor control technology andlaunches a comprehensive study from the aspects of theory and practice on several key issues,mainly include the detection of the rotor position, the rotor pre-position, PWM modulation,torque ripple suppression and so on.This paper first introduces the basic principle and the mathematical model of thebrushless DC motor. Analysises the back electromotive force (EMF) zero-crossing detection,which is the most mature technology of the rotor position detection technology. And gives thelagging30°electrical angle commutation method. Then, the start strategy for brushless DCmotor is discussed. The principle and main points of three step starting stragegy are descriptedin detail. For PWM modulation issuse, based on the comparing of several common PWMmodulations, the ON-PWM modulation scheme is choosed. After analyzing the reason for thecommutation torque ripple generated in the modulation scheme, this paper puts forward asimple and effective method to suppress the commutation torque ripple.This paper builds the simulation model of the brushless DC motor’s double-loop controlsystem in the Matlab/Simulink environment and conducts simulation experiments of thesystem. Then, based on TI’s DSP chip TMS320F28015the sensorless brushless DC motorcontrol system is designed. The hardware and software design of control system are alsodescribed in detail. Finally, the various aspects of the control system are verified byexperiments. And the expected results are achieved.