Research On The Method For Zero Start-up Of Sensorless Brushless DC Motor

Brushless DC motor(BLDCM) has a simple structure without carbon brush mechanical commutation, exeellent speed adjusting performance, high operating effieieney, low cost , small in size , easy installation and maintenance etc. So in the field of agriculture, industry, defence and domestic electric appliances and so on, its application is getting more and more widespread. But, in order to detecting the rotor position must be installed three hall sensors in the motor. But hall sensors is very sensitive to temperature and damage easily. Therefore, Domestic and foreign began to do a large amount of research in detection of the sensorless brushless DC motor of rotor positions. But, these Control strategies still exist in the following defects, zero start-up performance is poor, easy to wager turn and back and often lose step phenomenon, And using complex software to get the rotor position increased costs.The paper quote a new approach to get the rotor position signals by detecting the line voltage difference of ZCP to solve appeal problems.This method can get the rotor position at 2% rated speed. So, the motor can start-up from zero speed rapidly use this method.The paper main study the BLDC startup control system ,it is suitable for the fans without rotor position sensor of inside or outside aire conditioning. First,this paper detailed the mathematical model of the BLDC basic on electrical characteristics of the motor.And getting the Mathematical expression of the method basis to further analysis and inferred.Second, this paper get a system model for line voltage difference method through MATLAB and the corresponding simulation in order to verify this method is correct and feasible, get line voltage difference of the mathematical model. we can see this method in the theoretical analysis and the simulation is completely feasible by the simulation results, which provides a strong theoretical support for follow-up work.Then, this paper analysis and design the hardware circuit (power circuit) and software. And it also presents the principle of the hardware circuit and the method of the parameters calculation. At the same time, software in order to overcome this situation that can not calculate the rotor position in the zero start-up stage, and the three-steps startup by using in software start-up stage ,and process tracking and failed to start treatment in this stage, ensure the start-up foolproof.Finally, BLDC drive PCB and power PCB have been tested through the sample machine that is setted up by myself. At last completed the brushless dc motor starting and control experiments. The results show that the system hardware is working normally, the software design is reasonable, startup in a low speed and stable and no obvious speed jitter. In conclusion, this study has reached the desired goals.