Follow-up control of brushless DC motor based on FOC algorithm

Abstract

The main research content of this paper is based on motor theory, power electronics technology, motor control theory, brushless DC motor research object, based on magnetic field oriented control technology to do further design and research of motor control algorithm.The work completed in this paper is summarized in the following parts: (1) By referring to a large number of Chinese and English references, this paper summarizes the cutting-edge technology and research hotspots of the motor control system, conducts a comprehensive research and analysis on the origin of the motor, the development history of the controller and the general situation of the motor control strategy. In order to achieve the servo control of the motor, the FOC algorithm is used in this project to output sine wave to drive the motor control system. The angle position information of motor is obtained by encoder. (2) The core components of the brushless DC motor are introduced, the rotor and stator structure and material selection characteristics of the motor body are introduced, the rotor position detection and the working principle of the electronic commutation circuit are introduced, and the corresponding connecting circuit is built according to the working principle of BLDCM. (3) The principle and control flow of FOC algorithm are introduced. The coordinate transformation and the analysis and judgment of the sector are explained in detail. In particular, park transform and Clark transform are analyzed in detail, including the related formulas and calculation process are described. (4) In terms of software design, the features and advantages of the STM32CubeMX integrated development environment are first introduced. The hardware abstraction layer of CubeMX can conveniently select the required pins and automatically generate the initialization program, which greatly simplifies our subsequent code writing work. In addition, the program structure diagram is designed and the realization process is described in detail. At the same time, the main algorithm program function and some relatively important program code in the main function are given, including: duty cycle calculation, electrical angle calibration, speed measurement, etc. The pulse width modulation principle of motor control is introduced, and the program code of PWM pulse output is given. Finally, the realization of lower closed-loop control and PID algorithm is introduced, and then all the designed hardware circuits and hardware devices are connected according to the sequence of signals, and the design and welding of the entire BLDCM hardware circuit is completed, including: The circuit module of IGCMF15F60GA minimum system, the circuit module of power supply circuit and the encoder module of real-time detection of rotor position information play the role of core control. After the experimental platform was built, the KEIL MDK V5 debugger was used to download the compiled program code to the control chip through STLINK V2, and finally the motor was tested to be able to follow up control according to the plan. The test results show that it is feasible to use the FOC algorithm as the brushless DC motor servo control scheme, the control precision of the brushless DC motor is improved, and the motor fluctuation and noise intensity are suppressed to a certain extent. The brushless DC motor designed and realized in this paper is driven by FOC algorithm to achieve a servo control system, which is completed smoothly. Under the control of the algorithm, the output of the brushless DC motor can be started smoothly, and the speed of the motor can be adjusted without pole or the angle of the electric machine can be locked while the servo control is completed, and the automatic reset can be achieved when external forces are applied. In addition, in the experiment, the noise generated by the motor is very small, and the one-to-many control makes it more suitable for a wide range of applications in factory production and residential life. The brushless direct current motor has the good speed regulation performance of the DC motor, and can achieve uniform and smooth stepless speed regulation under heavy load. At the same time, compared with the traditional brush DC motor, there is no motor contact caused by brush friction commutation, no power generation and other problems. Therefore, it has been widely concerned by industry workers and scholars. Under normal circumstances, the follow-up control for brushless DC motor is generally square wave control. However, when the square wave control is started, the fluctuation is large and the noise is large, which seriously affects the industrial application environment, which causes a great challenge to the practical application of BLDCM. On the other hand, FOC adopts sine wave control mode, which can start smoothly and mute the whole process, and fundamentally solve the noise problem caused by square wave control. Moreover, this control mode divides the stator current of the motor into excitation current and torque current according to the set relationship. The accuracy and rapidity of speed control are greatly improved. Based on the above situation, the study of brushless DC motor FOC algorithm servo control has important theoretical value and practical significance. This thesis focuses on the follow-up control system of DC brushless motor based on FOC algorithm, and the specific research content is summarized as follows: Firstly, the thesis introduces the research background and significance of brushless DC motor and its drive control system, focuses on their research status and development trend, and introduces the structure and working principle of brushless DC motor. Then, this thesis introduces the basic control principle of FOC algorithm, expounds the corresponding control theory and coordinate transformation theory in detail, and gives the sector calculation process. The servo control system of BLDCM is designed based on FOC algorithm, and the specific control flow is given. Finally, this thesis uses IGCMF15F60GA as the main controller chip of the control system to build the corresponding hardware experiment platform, and carries out joint debugging and testing of the BLDCM system based on FOC algorithm. The experimental results show that the brushless DC motor using the FOC control algorithm can achieve stable operation, and at the same time, it can also achieve the stepless adjustment of the motor speed or the lock of the electromechanical angle while completing the follow-up control function, and can realize the automatic reset under the application of external force. The noise generated by the motor in the experiment is very small.