Research On Drive System Of Brushless DC Motor And Its Stability

Brushless DC motor (BLDCM) has so many advantages such as a high operating efficiency,no excitation loss and good speed-governing performance, and also a simple structure,reliable operation and easy maintenance. So it is been widely used in many fields. With thedevelopment of power electronics technology, micro-processing technology and new controltheory, as well as the development of permanent magnet materials and gradual reduction ofbrushless DC motor, it has a more and more wide use in high-performance speed-governingmotors and military servo-control systems. While higher requirements for the brushless DCmotor drive system, control system performance and its stability are put forward. The issuethat to solve the problem of not ideal drive and control performance of BLDC motors, needsfurther study, including the methods and implementations of power modules and drivetechnology, as well as stability at full speed domain, especially the filtering problems.Firstly, the drive system of BLDC motor has been researched. The control strategy ofPWM regulator is put forward after the analysis of the structure and operation principle of theBLDC motor.Then the design of the hardware system and the so ftware system wereintroduced. The hardware system includes three parts: the control circuits with a DSP chip asthe core, the driver circuits with the main functions of rectifier and inverter and the detectionand protection circuits. The software system includes the processing of position signal fromthe sensor, calculation of speed and PI regulations of speed loop and current loop, with mainfunctions of stator commutation and speed governing. There are also introduction of functionmodules, such as motor start module.After the design of motor drive system, the issues of the stability of BLDC motor driverhave been proposed, about the minimum running speed and torque ripple. Then the methodsof achieving the minimum running speed and the strategies of suppressing the torque rippleare proposed. And a method of the achievement of digital filters based on Freescale-56800chips is also proposed. Finally, the experimental test of the designed drive system of the brushless DC motor isperformed. The results show that the drive system can drive the brushless DC motor runningnormally. Also the filtering effect of the digital filters is validated. The result shows that thedigital filters can effectively suppress interference signals. Basing on the platform o f thebrushless DC motor drive system, this paper has a research of the stability of the brushlessDC motor. It has great significance for the study of brushless DC motor.