| Acoustic emission signal source acquisition is very important in the research process of acoustic emission detection technology.At present,it is difficult to ensure that the acoustic emission source signal is stable and consistent,and it needs manual operation.Therefore,in order to meet the needs of sound emission signal waveform generators with good repeatability,high stability,and programmability in the research of sound emission detection technology and equipment,this thesis uses electrical signals to stimulate transducers to develop simulated sound emission signal sources.The research will provide experimental conditions for the research of acoustic emission detection technology of helicopter hub components.In this thesis,based on the actual application needs of the source of the acoustic emission waveform,the system technical indicators and functional requirements are proposed.On this basis,a design scheme that effectively combines ARM,FPGA and direct digital frequency synthesis technology is proposed,and the crack of the titanium alloy material is completed.Hardware circuit design,software design and testing of acoustic emission signal analog generator system.The main work content and research results are as follows:1.Hardware circuit design.The system hardware is divided into the main control part of ARM microprocessor,FPGA+DAC waveform generation source and signal drive output part for design.Use STM32F407 as the main controller of the system,complete the control tasks such as human-computer interaction,network communication,data storage,and waveform amplitude by controlling various peripheral circuits,and perform data transmission through FSMC and FPGA to realize the control of digital signal sources.Use FPGA chip EP3C25E144C8 and high-speed D/A converter AD9764 and low-pass filter form a DDS waveform generation source.Two output channels are designed.One uses AD8065 to form an op amp circuit as a standard signal source output,and the other uses ADA4898 and PA85 to form a high voltage power drive circuit as an acoustic emission excitation source output.2.FPGA logic design.According to the working sequence of FSMC,combined with the analysis of the communication data,the design of the FSMC interface communication module is completed.The characteristics of the required synthesized waveform are analyzed and the waveform generation scheme is designed in conjunction with DDS to realize sine wave,raised cosine wave,Gaussian envelope sine wave,rectangle Pulse wave,AE double exponential envelope wave,AE triangle envelope wave and custom waveform generation.DAC interface and control module are designed to provide clock signal and digital waveform data for AD9764.3.System software design.Designed the micro-processing control program including touch screen communication,ethernet communication and various command processing.Designed the touch screen human-computer interaction program,through the touch interface to select the type of output waveform,set the waveform parameters such as frequency,amplitude,repetition rate,pulse width,and choose the function of each system.Designed the PC-side remote control software,so that the system has the function of custom wave generation and remote manipulation.After testing,the signal source of the acoustic emission signal analog generator can output a standard signal with a frequency of 10 k Hz～1MHz and a maximum amplitude of 5V.The excitation source can output an excitation signal with a frequency of10 k Hz～300k Hz and a maximum amplitude of 180 V And function in line with expected goals.Finally,by conducting a simulated crack acoustic emission signal test on a flat panel,the feasibility of generating an acoustic emission signal by electrical signal excitation was verified. |
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