The Design And Research Of Sensorless Control System For Brushless DC Motor

With the development of science and technology, people's requirement for dc motor is continuously improved,so they are not satisfied with the traditional brushless dc motor in all kinds of disadvantages exist in industrial applications.Sensorless brushless dc motor using indirect measurement method of rotor position instead of using the sensor detection method,it can effectively solve many problems caused by sensor, so the research of its control system is of great significance.This topic focuses on the research of the small sensorless brushless dc motor,expounds the advantages of non sensor in industrial production, the existing non-inductive control principle, including the rotor position detection, such as start-up methods conducted in-depth research, this paper analyzes the counter electromotive force and the basic principle of the zero test in the practical application in the process of commutation position detection and motor, designed based on Atmega8 control core non-inductive brushless dc motor control system.Paper first introduces the non-inductive basic structure and operation principle of brushless dc motor, and build up its mathematical model.Secondly from the rotor position detection method, the motor start and PWM modulation method three aspects introduced the domestic and foreign existing motor control scheme, by comparing the identified theory needed to use the control method in this paper.Then has carried on the system hardware design, in the required functionality has been clear about the system, on the basis of drawing the voltage detection circuit and communication module circuit, current detection,in mastering the six arm based on the principle of full bridge drive drive circuit was designed, and to counter electromotive force the zero test and commutation principle based on back emf detecting circuit is designed.After the system software design, adopted the modular design ideas, using C language to write the current voltage detecting module, timer and PWM module, zero crossing detection and commutation module, start the corresponding program module and communication module.Finally, this paper has carried on the experiment to the designed control system, get the waveform in the motor is running.Test results achieve the expected effect, can make the motor normal and smooth operation.