Design Of Brushless DC Motor Controller And Research Of The Control Algorithm

The brushless DC motors (BLDCM) have the advantage of small sizes，low weight，and easyto maintain．So it has been widely used in every field of industrial control．The traditional methodof controlling BLDCM requires position sensors for commutation and current control, but mountingposition sensors will bring a number of drawbacks, furthermore, in some special application filed,the sensors is not suitable. And this restricts the industrial drive applications. After the attachmentof sensorless control，it，This paper mainly researches the sensorless control technology forBLDCM, designs and develops a control system for BLDCM without position sensor.At the beginning of this thesis, the background and research significance of this subject isintroduced, and also the current status of brushless DC motor research and future trends is given.Then this paper detailedly discusses and analyzes basic structure，the operational principle andmathematical models of BLDCM, which provides theoretical basis for motor control.In the following chapters, this thesis mainly elaborates the key technologies of sensorlesscontrol, including the position detection technology, dual-boot technology and double closed-loopcontrol strategy. First of all, the paper analyzes principle of EMF method for position detection,especially illustrates the terminal voltage way to detect position，and also shows the hardwareimplementation of back EMF zero-crossing detection method. For motor with sensorless control, itis difficult to start, this paper describes several commonly used methods to resolve the startingproblem, and in the section of system software design, we give an improved method of pre-positionstart. In order to improve the speeding performance, we adopt the double closed-loop controlstrategy of speed and current, this paper describes the principle of double closed-loop speed control,and combined with the motor mathematical model, we use MATLAB/Simulink to establishsimulation model of two-loop speed control system，we do research with this model，verify thefeasibility of double-loop speed control scheme, and provides references for PID parameterchoosing of software debugging.Finally, choosing an appropriate scheme, designing a controller of brushless DC motor andsome experiments are carried out for this control system. In the part of hardware circuit design, thepaper expounds the whole scheme of hardware design firstly, and then introduces the main circuitsin detail, also the paper gives the basis of devices selection and method for parameter selection ofthe main components. We use the STM32 MCU as the core microprocessor of hardware system.The power inverter circuit is designed with Intelligent power module FSBB30CH60，it can supportdriving application for BLDCM when the maximum DC voltage is 550V and the maximum currentis 15A. The position detection circuit which is based on the theory of EMF is simple and reliable. With the software, we can accurately capture the back-EMF zero-crossing signal, which providesposition information of rotor. In the part of the software system design, the paper introduces thegeneral framework of software firstly, and detail various modules of the software in the sub-sections,including software for controlling the motor starting, the rotor position detection signal capturing,H_PWM-L_ON modulation, motor speed calculation, current and voltage signal sampling anddouble-loop PID control achieved.The results of the experiment show that the rotor position detection system can accuratelydetect the location of back-EMF zero-crossing signal, thereby ensuring the correct motorcommutation and stable operation. The control system can control the brushless DC motor startingsmoothly, stepless speed motor can be achieved, and at the same time, the running state of motorcan be monitored in real-time, including speed, current, voltage.