Research Of Alternating Magnetic Field Therapy System Based On STM32F4

Related research shows that the alternating magnetic field has a great influence on the microcirculation, osteoporosis and meridian. As there is no magnetic therapy instrument with alternative magnetic field which has wide range, stepless adjustable frequency and stepless adjustable magnetic induction on the market, a medical company commissioned us to design and develop a system to meet the application requirements. On the basis of reference at home and abroad on the therapy instrument and combined with system requirements and related technologies, finally the design scheme of alternating magnetic field therapy device based on STM32F4 is determined.The control system started from the decomposition of application requirement of alternating magnetic therapy instruments, then a variety of solutions were put forward to realize each subdivision of the requirements, finally the best solution of each subdivision was selected. A lot of work was done to realize the system, such as the study and application of embedded real-time operating system uC/OS-II, the design and debugging of circuit and program for serial port screen, the design and debugging of program and algorithm for SPWM, the design and debugging of program and circuit for AD7606, the design and debugging of driver circuit for MOSFET, the design and debugging of the serial driver circuit for DS18B20, the design and debugging of circuit for opposite type ultrasonic module, the design and debugging of multiple protection circuit for relay contact, etc.Some theories were applied to achieving the system, such as the SPWM theory to modulating the output waveform of the inverter, helmholtz coils theory to producing the required magnetic field space, series resonance theory to add capacitor in series to load circuit to reducing reactance when the high-frequency current through the inductive load, PID algorithm theory to improving the control precision of magnetic induction. Some improvements were made to increase performance of the system, for instance, a bipolar SPWM algorithm with dead zone was proposed, a high-quality output inverter with variable voltage and variable frequency based on STM32F4 was achieved, the simple and effective interlock signal circuit of driver for H-bridge was realized, the problem of non-contact distance measurement of treatment in small space by using opposite type ultrasonic was solved.At present, the main function of the alternating magnetic field treatment instrument has been realized and the development process has entered final stage of system debugging. The tests show that results of testing are consistent with theoretical calculations results and simulation results. Measured results show that the SPWM algorithm is accurate, the design of circuit is correct, measures to solving the problem is feasible and the overall design is reasonable.