Research Compare On Sensorless Control For Brushless DC Motors

Compared with the traditional DC motors, brushless DC motor (BLDCM) notonly overcome the low efficiency, produce sparks during commutation and shortlife; but also have good adjust performance, high starting torque and so on. Withthe development of power electronic devices and permanent magnet materials,lower prices, especially in the emergence of NdFeB materials, make the BLDCMaccelerated development.With the wide range of applications in various fields ofBLDCM,the traditional position sensor control system has been diffcult to adapt tothe industry needs,the position sensorless control method has become the researchfocus of the BLDCM.This article describes the structure and work principle of the BLDCM. Thecommon methods of sensorless control of BLDCM are presented，and the principleof back-EMF method is introduced in detail, on this basis, introduced the improvedback-EMF method.This two kinds of methods of the zero-crossing of back-EMFsensing are analyzed. The common start methods of sensorless BLDCM controlsystem are introduced, and the three-step start technique, including the rotorpre-setting, accelerating and the state-changing step, is discussed in detailed.The control system used the Freescale’s MC56F8013digital signal processoras the main control chip, according to the requirements of the control system builtthe hardware platform, including the control power supply circuit, inverter maincircuit, drive circuit, the rotor position detection circuit, voltage and currentsensing circuit, fault protection circuit. The software platform used in the DSPintegrated development environment Codewarrior, according to the control systemrequirements used the C language programming, debudding, etc, and each part clearand concise, easy to modify, debug and transplantation of the program.Finally, the entire BLDC control system designs to achieve, and using the1.7KW outer rotor brushless DC motors as experimental subject in thelaborrtory-built experimental platforms and the experimental results are given. Atthe same time, the paper summarizes the research work and the prospect of furtherresearch work.