| Brushless DC motor with Permanent magnet excitation, in which electrical commutator is used instead of mechanical brush and commutator, has the same good characteristics of speed control as traditional DC motor. Brushless DC motors have found wide application due to their high power density and ease of control. Moreover, the machines have high efficiency over wide speed range. Attachment of sensorless control not only overcomes a lot of disadvantages generated by the sensor, but also expands the application range of brushless DC motor further. In recent years, sensorless brushless DC motors control technology had become one of the hot researches.The thesis closed the hot research, a set of sensorless brushless DC motor control system was designed to control square-wave brushless DC motor. The system used TMS320LF2407A DSP as the MCU, used the method of BEMF (back electromagnetic force) zero-crossing detection and starting method which combined the rotor pre-setting method with the increase-frequency and increase-voltage method to carry out the control of the brushless DC motors. In order to improve the speeding performance, the two closed-loop control strategy of speed and current were adopted.First of all, the paper researched the brushless DC motor of the fundamental structure, performance, operational principle and mathematical model. And the simulation model of the brushless DC motors was established in the Matlab/Simulink based on the mathematical model, and the overall design program was proposed based on the simulation model. Surrounded some pivotal techniques of sensorless brushless DC motor control system like the principle and method of BEMF zero-crossing detection and phase compensation, starting, single neuron PID controller and PWM produce circuit, the paper had held a deep research.The second, the paper carried on the software and hardware design based on the overall plan and the function requirements of the system. In the hardware design, they were introduced mainly to the smallest DSP system, current and rotor position detection circuit, IR2130 driver circuit. And in the software design, the main program which included DSP system setting, variable initialization, motor positive &negative setting, starting, calculating and displaying of speed, and A/D interrupt subroutine which included calculation of BEMF, calculation of commutation time and current speed adjustment subroutine and others were designed.At last, experimental results showed that the motor started fast and stable with wider area of speeding. This brushless DC motors control system had the characteristic of simple structure, high dependability, and can be used in many fields. |
