Micro External-rotor Bldc Motor And Its Control

Sensorless brushless DC motors(SBLDCM) have been widely used in the field of aeromodelling with the advantages of small size, light weight, high efficiency and reliability. Brushless DC motors(BLDCM) can be categorized into external rotor BLDCMs and inner rotor BLDCMs due to the different structures. This paper designs an external rotor BLDCM and its control system.Firstly, according to applications, this paper designs the structure of the motor and establishes the simulation model by ANSYS. Based on this simulation model, the design of this motor is optimized to minimize cogging torque. A series of hand made prototype motors are made in accordance with the result of optimization.Secondly, this paper introduces the working principle of BLDCM, the position sensorless techniques and various method of pulse width modulation. The simulation model based on SIMPLORER is established for analyzing and designing the control system of BLDCM. The traditional method of motor start-up is introduced, and then an improved method based on the three-step start-up is presented for solving the starting problem of SBLDCM.Finally, a control system based on BUCK convertor is built. A controller based on MSP430F149 is also designed. This paper detailedly introduces the hardware composing of the controller, and explains the function of important components. And program flowcharts are also given. Verification experiment is completed.