Research On Control Technology Of Free Induction Heating Based On STM32 Microcontroller

Electromagnetic induction heating technology has been widely used in industrial, domestic, and medical heating due to its advantages of efficiency, fast heating, safety, cleanness, and accurate control. In recent years, the design direction of the heating surfaces of the electromagnetic induction heating products is towards flexibility and diversity. The thesis designed a free induction heating system with flexible heating surfaces,which is based on the principle of electromagnetic induction heating and the main control chip STM32F407.Free induction heating system chooses the microcontroller STM32F407, produced by ST Microelectronics, as the core processer. The processer is based on ARM Cortex-M4 core at a frequency up to 168MHz; it features 144 pins which is sufficient to connect dozens of induction heating coils. It also incorporates various peripherals; the timer can generate the control signal needed by the systems. There is also a FPU and a DSP instruction which support the functions of high-speed floating point and DSP processing. On the other hand, the ST Company has a series of high-performance processors, which is convenient to expand and upgrade in the software and hardware of the heating system.Firstly, the thesis briefly introduces the development and the current situation of induction heating and free induction heating. Then the related key technologies such as the analysis of the working process of the resonant inverter circuit, the multiplexing heating technology of free induction heating system,the embedded technology and the selection of the microcontroller,are analyzed. For the principle of the realization of the system function, the thesis mainly analyzes FFT technology, FIR filtering technology, the principle of the load detection, the adjusting principle of the resonant frequency after the load changes and the principle of power control. Secondly, in the design of the system hardware, the unit module is divided by functions; the unit circuits are the main circuit, the driving of IGBT circuit and the peripheral circuits related with microcontroller. According to the focus of the thesis, the thesis mainly introduced the design of micro-control module circuit and peripheral circuit. Finally, in the part of the design of software, control system for software, the thesis introduces the popular software Keil MDK and the STM32F4 firmware library in detail. In the design of the program, in line with the division of hardware circuit module, modular program design is used and the main software control modules include system initialization, A/D data acquisition and processing, monitoring, power controlling, human-computer interaction, interrupted procedures, and so on. At last, the system’s software and hardware are debugged at the same time; the result indicates that the system can work in normal and steadily and achieved predetermined functional requirements of the system.