Direct Torque Control Of Brushless Dc Motors

With the development of power electronics technology, modern control theory and the new permanent magnet materials, permanent magnet brushless DC motor and control technology has been a breakthrough. Permanent magnet brushless DC motor has been applied in aerospace, industrial and household appliances and other fields widely with its high efficiency, low noise, easy maintenance and many other advantages. However, in the low-speed operation, torque ripple generated in commutation period is the main drawback of BLDCM, which make the application of BLDCM in the high accuracy system impossible. Direct Torque Control technology is developed as a kind of AC Driver in the 1980's. the model is analyzed in the stator coordinate, the stator flux space vector and electromagnetic torque as variables is controlled, the purpose is to control the electromagnetic torque directly, the method is more simple and rapid, and improve the dynamic response of the system further.In order to reduce the torque ripple, the technology of Direct Torque Control of brushless DC motor is researched in this people. the brushless DC motor structure and principle is analyzed detailedly. Because of the stator flux trajectory is a regular hexagon, It may not be controlled the flux, only control its torque, thereby simplifying its control system greatly. The model of BLDCM is established.Based on detailed analysis of the theory of direct torque control, the scheme is designed about the BLDCM-DTC. use the approach of space voltage vector modulation, The Methods of back-EMF is used to detect the signal of rotor position to achieve sensorless motor control. based on Matlab/Simulik software, the simulation model of brushless DC motor and improved direct torque control system is established, and the study of simulation is implemented.Simulation of BLDCM-DTC is operated in both No-load and load cases, and the results are compared and analyzed. Simulation results show that the scheme of DTC, not only is designed to be simple, easy, but also the motor which is running regardless of what kind of work in the state, can inhibit the torque ripple effectively, the system has better dynamic and static performance, have some value of practical significance and promote. Followed the simulation, the hardware and software control system are designed based on the core of DSP TMS320F2812. A solid foundation is made for the follow-up study of BLDCM-DTC.