Design And Investigation Of Brushless DC Motor Vector Control System Based On Hall Sensors

Brushless DC motor(BLDCM) is a new kind of permanent magnet motor which is rapidly developed in recent years with the wider use of power electronics technology, microelectronic technology and the improved permanent magnet materials. BLDCM not only has the advantages of AC motor, such as the simple structure, high running reliability, but also has the features of DC Motor, such as the high efficiency, excellent adjusting speed characteristic. Therefore, it is widely used in the fields of the household appliances, transportation, and aerospace, etc.Three-phase hall sensors are used in traditional BLDCM control system because of low cost, and the corresponding six-state square wave control method based on discrete rotor position signals are used. although this control method is easy to implement, it demands the Back-EMF to be trapezoidal. But in fact, due to manufacturing reasons, the ceiling of Back-EMF waveform of BLDCM is difficult to reach 120°. Methods to reduce cogging torque such as rotor skewing are often used in the design of BLDCM. These make the Back-EMF waveform more sinusoidal. Using square wave control method on this kind of BLDCM will cause current and torque ripple. To solve the problem, a vector control system of Sinusodial BLDCM based on hall-effect sensors is proposed.In this thesis, firstly, mathematical model of sinusoidal BLDCM is derived, BLDCM vector contol system is established based on this. Methods of rotor position estimation based on hall sensors are introduced in detail. Effects of installation deviation and output characteristic of hall-effect sensors on estimating precision are analyzed. Methods of improving estimating precision are proposed.Secondly, an experiment platform of this control system is set up based on dsPIC30F4011. Software and hardware designs are completed. Software system of the platform includes vector control MCU programme and monitor software development. Hardware system includes motor drive power circuit, MCU control circuit, signal modulating circuit, serial communication circuit, etc. Two outputs switching power based on TOP222Y is designed to supply low voltage circuits, Boost PFC based on IR1155 is designed to improve system power factor.Finally, investigations on static and dynamic performance of the control system are done based on the designed experimental platform. The experimental results show that the system has good static and dynamic property and prove the correctness and validity of the design.