| Brushless DC motor with permanent magnet excitation, in which electrical commutator is used instead of mechanical, 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. They are used in industries such as Automotive, Aerospace, Consumer, Medical,Industrial Automation Equipment and Instrumentation. 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. At present, Sensorless control has become a development trend of control technique for brushless DC motors.Firstly, this thesis introduces the background, development and future prospect of brushless DC motors, analyzes operational principle and the mathematical model of the brushless DC motors. Compares with the sensor brushless DC motors control system and sensorless brushless DC motors control system. Introduces the methods of the sensorless brushless DC motors control, and selects the BEMF (back electromotive force) zero crossing method to realize the sensorless brushless DC control.The thesis introduces hardware and software design of the Sensorless Brushless DC motor control system which is based on TMS320LF2407A DSP. Their structure and function are described in detail, and the EMC design of the system is described.More experiments studies on the startup method of Sensorless Brushless DC motor, and finally realized the small capacity Sensorless Brushless DC motor control.
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