The Design And Realization Of The Sensorless Brushless DC Motor Control System

As thefeatures of simple structure, high efficiency and easilycontrolled,brushless DC motor (BLDCM)is widely used in aerospace, householdappliances and electric drive and other aspects. It not only has advantages oftraditional DC motor, such as easily controlled, high speed performance and highefficiency, and so on, but also has advantages of traditional AC motor, such asbrushless and conveniently repaired,and so on. It becomes a hot topic in field ofmodel motor. However, rotor position sensor of BLDCM has heavily increasedmotor’s volume and cost, and greatly limits the applications of BLDCM. Therefore,sensorless control, which has wide significance, has becomes one of the hot controlmethods of BLDCM.At first, this article describes the BLDCM has got more and more attention forits’excellent performance and statues BLDCM rotor position detection technology’spresent situation and development trend,which becomes one of the hotspots. Itcompares hardware and software two kinds of position detection technology andmakes a conclusion that software detection technology, i.e. sensorless contr oltechnology will become the development trend of BLDCM controlling.Second, this article introduces the basic structure and working principle of theBLDCM and establishes a mathematical model of BLDCM. Based on the theory, acontrol strategy of the sensorless BLDCM, which is composed by the back EMF zeromethod and three-stage start-up method, is proposed and studied. For back-EMFzero-crossing method, it studies the principle of obtaining the rotor position, themethod of extracting the back EMF zero method and the error compensation. Itestablishes the Matlab/Simulink simulation model and gets simulation results. For thethree-stage start-up procedure, it detailly analysises three stages: the positioning stage,the acceleration phase and the switching phase. What’s more, it also shows a specificembodiment of the method.Finally, based on the theory proposed, this paper designs the software platformand hardware platform of the BLDCM sensorless control system and analyzes theresults of the experiment. The core of hardware platform is dsPIC33FJ16MC304chip,which has16bit channels and motor control high performance digital signalcontroller. The hardware consists of a three-phase bridge inverter circuit, drive circuit,brand-pass filtering back-EMF detection circuit and the protection circuit m odule, and so on. The software platform based on MAPLAB V8.78environment consists of twoparts: main program module and interrupt program module1.The results of theexperiment verify that in the no-load and light load conditions the platform ofsoftware and hardware introduced in this paper can stably control the sensorlessBLDCM system, and has a strong anti-interference ability.