Design Of Three Phase BLDC Motor Control System

Three phase brushless DC motor (BLDCM) with permanent excitation, whose electrical commutator is used to instead of mechanical, has not only the same good characteristics of speed control as traditional DC motor, but also the good characteristics of AC Motor such as structure simple, operation reliable, maintenance friendly . Brushless DC motor has set wide application due to its high power density, ease to control, high efficiency over wide speed range.The paper firstly introduced the study status of permanent magnet brushless DC motor in home and abroad, and then discussed its structure, operation principles, characteristics as well as its rotor position signal detection methods in detail; secondly, designed the control system's hardware and software accordingly; at last debugged the control system, analyzed the factors affecting the reliability of the system and gave the corresponding solutions.According to the requirements of control system such as design parameters, cost and flexibility, this paper designed Atmega8L SCM and ECN30206 integrated driver as the core hardware platform. Atmega8L SCM posed rotation speed PID closed-loop control on the system and regularly collecting current signal for the current over-current protection; used the Max7219 serial display the current, related to fault information; controlled Permanent magnet brushless DC motor's rotate direction and received external information, through the isolation of the photoelectric; exchanged information, analyzed and processed the various information, coordinated various parts working through the RS-485 bus interface with other outside systems.This paper compiled a program based on the hardware platform to coordination with the hardware. The software of the control system is comprised by one fore-and-aft platform main program and two interrupt service subprogram. The fore-and-aft platform main program is made up by the system initialization module, the rotor speed computing and PID speed closed-loop control component. The system initialization module mainly initializes the three timers, A/D converter, serial UART, I/O pins. After system initialization, the main program computes the BLDC's rotor speed and compared to the set speed value and then it send the error to the PID control. The PID controller will change the voltage of the ECN30206 integrated driver's VSP pins according to the duty cycle of PWM. In this way the rotor speed was controlled accord with the user's setting value. One of the interrupt subprogram mainly used to receive the control order from the external system, which composed of rotor direction, rotor speed value. The other is mainly used to detect the current and display the speed and related failures regularly.In this paper, the brushless DC motor control system achieved the rotor direction, speed closed-loop PID control, and various parameters defect display. The control system has a perfect protection, simple hardware structure, lower cost. The main control section, driver section and display section can choose arbitrary by the user.