Research And Development Of Ultrasonic Power Supply With Frequency Auto-tracing And Constant Amplitude Control Based On STM32

Ultrasonic assisted machining technology is a kind of composite processing method combining ultrasonic vibration system with the traditional processing methods,which in recent years has achieved rapid development and wide application in machining hard,brittle and difficult to machine materials.As the core of ultrasonic vibration system,the ultrasonic power system directly affects the vibration effect of the tool and the quality of the machined surface.With the application of various advanced hard brittle composites and the higher processing quality requirements,the existing ultrasonic power supply technology has been unable to meet the requirements of high frequency output and rapid dynamic response.In order to solve the above problems,an ultrasonic power system with automatic frequency tracking and constant amplitude control is developed with high speed processor STM32.The main research contents can be divided into three aspects:(1)The hardware of the ultrasonic power supply system is comprehensively analyzed and optimized.The function modules of the ultrasonic power supply are redesigned and simulated.The AD9850 chip is used as the high frequency signal generator by DDS technology and the corresponding control method is given.The full bridge MOSFET inverter bridge is used as the high frequency inverter,and the full bridge driving circuit is designed by using the IR2110 driver chip,and the negative voltage circuit is optimized.The series inductance method is used to design the matching circuit of the ultrasonic transducer.In order to realize the automatic control of the ultrasonic power supply,a simple and efficient current voltage feedback circuit and so on are designed.(2)Three software algorithms with fast response capability for automatic control of ultrasonic power supply are proposed and implemented.The first is a fast frequency sweep algorithm based on dichotomy.The algorithm can quickly find the resonant frequency of the transducer and speed up the system initialization speed in the starting stage of the ultrasonic power supply system.The second is the automatic tracking algorithm of frequency output,which is based on fuzzy PID theory.Fast tracking of frequency output can be achieved when the resonant frequency of the transducer is drifting.The third is the amplitude constant control algorithm.On the basis of the frequency automatic tracking,the algorithm realizes the regulation of the voltage of the power supply by the chopper to achieve the purpose of constant amplitude control of the transducer amplitude.(3)The test platform of the ultrasonic power system is built to verify the static output and dynamic performance of the ultrasonic power supply.In the process of testing,the design and optimization of the ultrasonic power supply system have been iterated many times.Finally,the ultrasonic power supply can satisfy the high frequency characteristics of 20-50 KHz output and the automatic tracking performance of fast frequency.In addition,a single factor test was designed,and the difference between the ultrasonic assisted grinding C/SiC material and the ordinary grinding method in the grinding force was compared and analyzed.The constant amplitude control and dynamic response ability of the ultrasonic power supply were verified by monitoring the output state of the ultrasonic power supply during the process of processing.The experimental results show that the ultrasonic auxiliary grinding has significant advantages,such as reducing the grinding force and prolonging the life of the tool,and further proves the good performance of the ultrasonic power supply in this paper.