Preliminary Study Of Designing Sensorless Brushless DC(BLDC) Motor Drive For Medical Operation

Brushless DC motor is more and more widely used in the field of medical devices, consumer electronics, home appliances and industrial control etc. The traditional control methods of Brushless DC motor, which armed with the rotor position sensors, show out more and more limitations in practical applications, especially in the field of medical devices, handheld devices which armed with brushless DC motor should not only be light, compact, high efficiency, and less complexity, but also should be safe and stable in the conditions of high temperature disinfection and erosion of operation wastewater. Because of the special application environment and high requirement in applications, the limitation of the brushless DC motor in application is increasingly obvious. Therefore, researches of without position sensor detection methods got more and more attention, in which, because of its simple, easy to realize and high reliability and some other characteristics, back electromotive force method(BEMF) get more and more attention. It also has become a hot spot in rotor position detect methods research of Sensorless Brushless DC motor.In this paper, we will introduce the development history of the brushless DC motor, operation principle and mathematical model, and on the basis of that, we analysis the rotor position detect methods of sensorless, like the method of back EMF and the three harmonic method of Brushless DC motor. And design a system which based on micro controller of ARM Cortex-M3 to monitoring and control sensorless brushless DC motor. ARM chip LM3S811 has the characteristics of low cost, high performance, intelligent, and because of it, the system based on LM3S811 can simplify the system structure, reduce the cost of the system, and at the same time, the system is strong and multiple usable. With the data of pre experiment, the correctness of the rotor position detection method is verified. And at last, the overall system detection and control logic, motor starting method, rotor position detection method and motor control method are determined, system circuit is designed and the code is written.Finally, this paper established the TI company’s LM3S811 as the control core, combining the drive chip IR2101 of IR company, and Vishay Siliconix company’s power switch tube IRFR024, completed the system hardware circuit design. At the same time, the program flow chart is given, and make detailed introduction. The program was written in Keil for ARM. And in the end, through a simple analysis of the operation of the motor, demonstrates the correctness and feasibility of the detection method.