Research Of The Sensorless Digital Control System Of The BLDC Motor

Brushless d.c Motor has found wide application in many areas, in which electrical commutator was used instead of mechanical commutator, so it not only had the same good characteristics of speed control as traditional d.c Motor, but alse is more effectively and smaller. Moreover, sensorless control not only overcomes a lot of disadvantages generated by the sensor, but also expands the application range of brushless d.c motor. At present, sensorless control is a trend of control technique for brushless d.c Motors.The disadvantage of Brushless d.c Motor is that its excitation can't be control because of using permanent material excitation. The research focus of Brushless d.c Motor control system is: how to widen the speed range of Brushless d.c Motor; how to improve the precise of currnet regulation and reduce torque ripple; how to implement Brushless d.c Motor sensorless control. The dissertation studies on the control principle of the sensorless Brushless d.c Motor. At first, the dissertation introduces the basic elements, basic working principle, operating characteristic and transfer function of the Brushless d.c Motor, then it presents the disadvantages of sensor control and the means of how to use it in brief. For detail, the principle of commutation torque ripples is analyzed. According to the analysis and deduction, a compensation method has been putting forward creatively to reduce the torque ripple generated by commutation. The dissertation also makes qualitative analysis of field-weakening of Brushless d.c Motor.After the analysis and comparison of various detection technologies of the sensorless position, this dissertation chooses Back e.m.f zero-detecting. According to the demands of constant torque operation under base speed and constant power operation beyond base speed. This dissertation designs twain mode control system that is based on DSPIC30F6010 chip, and makes detailed introduce about the hardware and software of control system. This dissertation expresses the detection principles and algorithms of Back e.m.f zero-crossing and how to make the algorithms to come true. At last the dissertation makes detailed discussion about the software development for state switch strategy, designing start-programming, zero-testing procedures and how to avoid weakening the wind magnetic field.Motor body model is built in Matlab according to Brushless d.c Motor principles and mathematical mode. The simulational models are constructed based on...