BLDCM Sensorless Control System Based On DSP2407

Recent years, with the development of power electronic technology, motion control technolegy, material science technology and computer technology, brushless DC motor, which works as a kind of electromechanical switching equipment has been developed rapidly. Its application has extended from military to transportation, gauges, chemical engineering, medical science and many other areas. Brushless DC motor has the capability of simple structure, operational reliability and excellent speed regulation performance. Compared to a brush DC motor, brushless DC motor uses electronic commutator to take the place of traditional mechanical commutator. This method could avoid the spark coming from the process of commutation and the electromagnetic interference, and the service life and reliability of the motor has been improved a lot. However, the installment for electronic rotor posture sensor would increase the burden of brushless DC motor, which becomes a certain limiting factor to its application. As a result, the propound of sensorless brushless DC control system with profound significance has became a hot research point recently.In this paper, on the basis of detailed analysis for the structure characteristic and operation principle of brushless DC motor, sensorless brushless DC motor closed loop control system is realized. In the aspect of control algorithm, Back Electromotive Force (BEMF) is adopted to detect the triphase back electromotive force zero-crossing and then determine the position of the motor rotor, achieve the commutation process. At the same time, because of the starting problem brought about by back electromotive force, this paper puts forward a kind of "high-frequency pulse injection method" to detect the brushless DC motor rotor in the static position, along with "three-step startup method" and realize the motor starts smooth without reverse.In this paper, high-powered digital signal processor TMS320F2407 type DSP produced by TI is as the master chip, and ATmegal68 is designed as keyboard digital tube handheld unit control chip. In addition, the control system core hardware of the brushless DC motor, its peripheral circuit and a simple reliable back electromotive force zero crossing detection circuit are also presented. Modular control procedures using C language are edited combining with the characteristics of DSP and making full use of the resources.The experimental results show that the sensorless brushless DC motor control system could accurately detect the initial position of the motor and smooth start. On the basis of realizing the correct reversing and closed loop operation, the system has the functions of alarm display and double controlled both by keyboard and terminal. All of those proved the feasibility of this system.