Research On Soft Characteristic Speed Control System Of Brushless DC Motor

Brushless DC (BLDC) motor is a new generation of mechanical-electrical integration product. It not only has the good characteristics of the AC motor but also the good characteristics of the DC motor, such as its simple structure, operation reliability, easy-maintenance, high efficiency, easy-speed-control. Therefore, BLDC motor has been applied to many industry fields and every aspects of life. However, in special field where the motor with soft characteristic is needed, the application of BLDC motor was limited. In order to expand the application of BLDC motor, some research about soft characteristic speed control system of the BLDC motor was done in this subject.Firstly, BLDC motor control methods were researched. The effect of torque ripple of different control methods and PWM chopping methods of full controllable circuit were compared. A general used hardware was designed for all kinds of control methods according to the requirements of soft characteristic speed control system.Secondly, motor control application program was made on the base of SDK, and a double closed-loop speed control system was realized based on mathematical model of the BLDC motor. It has good stable state precision and established a base for the realization of soft characteristic speed control system.Thirdly, after the double closed-loop speed control system was established, the realization method for a soft characteristic speed control system was researched. And an application program was designed to realize the system. When realizing soft characteristic speed control, a method that uses current detection on the DC bus to measure torque was adopted. Testified by the experiment, the system is capable to react fast for load variation. And the motor is capable to run on the soft characteristic curve, whenever the load is added or reduced. All of these achieve the requirements of soft characteristic speed control system.