基于DDS和FPGA的数字式可变脉冲激励超声检测系统研究
发布时间：2018-10-17 09:46
【摘要】：超声波检测是铁路机车车辆零部件及钢轨无损检测的主要技术手段。国内外许多铁路部门都十分重视研发用于机车车辆零部件及钢轨无损检测的超声波检测设备。随着数字电子技术和现代计算机技术的发展,超声波检测设备由传统的模拟式设备向数字式检测设备发展。但是现今存在的超声波检测设备的激励脉冲比较单一,多为尖脉冲或方波脉冲,且脉冲的多个参数无法调节；对于大多数便携式设备,电源电压幅值较低,致使检测能力不够的情况,也没有采取相应补偿措施。基于此,本论文旨在研究和设计以现场可编程门阵列(FPGA)为核心、直接数字合成(DDS)技术为技术手段、辅以高速A/D的数字式可变脉冲激励超声波检测系统,通过可编程方式控制超声波激励信号的产生,以提高超声检测系统的检测能力和适应性,满足不同检测应用的需求。本检测系统采用直接数字合成(DDS)技术,通过可编程方式控制超声波激励信号的产生,使检测系统能针对不同检测需要,灵活设置和选择激励信号的波形、重复频率脉冲个数和脉冲宽度。同时,对影响激励信号性能的参数(脉冲类型、脉冲个数、脉冲宽度)进行了实验性研究,分析了各参数对激励信号能量的影响。提出在低激励电压条件下,以适当增加激励脉冲个数的方式来提高发射功率,从而提高检测系统的检测能力和适应性的新思想。论文以FPGA器件EP2C35F672为核心控制单元,采用模块化思想完成了检测系统的硬件电路设计,实现了超声波发射接收、程控放大、带通滤波、高速数据采集及人机交互等功能。硬件系统均采用噪声低、精度高和可靠性高的元器件,同时在设计制作时还采取了多种措施来保障和提高检测系统的精度和抗干扰能力。采用FPGA开发软件QuartusII完成了激励信号产生、时序控制、逻辑控制、数据采集、缓存等功能模块的设计与仿真,对软件设计的有效性进行了验证。在实验室采用CSK-IA标准试块对所设计的数字式超声波检测系统进行了功能测试。结果表明,多脉冲激励的方式能够在较低的激励电压下,获得更强的超声回波信号,实现工件内部更深范围内缺陷的有效检出。单脉冲激励方式在较低的脉冲宽度条件下,对分布位置接近的缺陷检测效果较好、分辨力强,可以很好的分辨各缺陷。本检测系统实现了超声回波信号调理、高速数据采集及存储的基本功能：可变脉冲的激励方式提高了检测系统的自适应及智能化程度,具有极强的实用性和研究价值。
[Abstract]:Ultrasonic testing is the main technical means of non-destructive testing of railway rolling stock parts and rail. Many railway departments at home and abroad attach great importance to the development of ultrasonic testing equipment for locomotive and vehicle parts and rail nondestructive testing. With the development of digital electronic technology and modern computer technology, ultrasonic testing equipment has been developed from traditional analog equipment to digital testing equipment. However, the current ultrasonic detection equipment has a single excitation pulse, most of which are sharp or square pulse, and the parameters of the pulse can not be adjusted; for most portable devices, the amplitude of power supply voltage is relatively low. As a result of insufficient detection capacity, no corresponding compensation measures have been taken. Based on this, the purpose of this paper is to study and design a digital variable pulse excitation ultrasonic detection system based on field programmable gate array (FPGA), direct digital synthesis (DDS) technology and high speed A / D (A / D). In order to improve the detection ability and adaptability of ultrasonic detection system, the generation of ultrasonic excitation signal can be controlled by programmable method to meet the needs of different testing applications. The detection system adopts direct digital synthesis (DDS) technology to control the generation of ultrasonic excitation signal by programmable method, so that the detection system can flexibly set and select the waveform of the excitation signal according to different detection needs. Number of pulses and pulse width at repetition rate. At the same time, the parameters (pulse type, pulse number, pulse width) that affect the performance of the excitation signal are studied experimentally, and the effects of the parameters on the energy of the excitation signal are analyzed. Under the condition of low excitation voltage, a new idea is proposed to increase the transmission power by increasing the number of excitation pulses properly, so as to improve the detection ability and adaptability of the detection system. In this paper, the FPGA device EP2C35F672 is used as the core control unit, and the hardware circuit of the detection system is designed by modularization. The functions of ultrasonic emission receiving, program-controlled amplification, bandpass filtering, high-speed data acquisition and man-machine interaction are realized. The hardware system adopts the components with low noise, high precision and high reliability. At the same time, many measures are taken to ensure and improve the precision and anti-interference ability of the detection system. The design and simulation of excitation signal generation, timing control, logic control, data acquisition, cache and other functional modules are completed by using FPGA development software QuartusII. The validity of the software design is verified. The function of the digital ultrasonic testing system was tested by CSK-IA standard test piece in the laboratory. The results show that the multi-pulse excitation method can obtain stronger ultrasonic echo signal at lower excitation voltage and detect defects in deeper range of workpiece effectively. Under the condition of low pulse width, the single pulse excitation method has better detection effect and strong resolution for the defect with close distribution position, so it can be used to distinguish each defect well. The system realizes the basic functions of ultrasonic echo signal conditioning, high-speed data acquisition and storage. The excitation mode of variable pulse improves the adaptive and intelligent degree of the detection system, and has strong practicability and research value.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB559
本文编号：2276277
[Abstract]:Ultrasonic testing is the main technical means of non-destructive testing of railway rolling stock parts and rail. Many railway departments at home and abroad attach great importance to the development of ultrasonic testing equipment for locomotive and vehicle parts and rail nondestructive testing. With the development of digital electronic technology and modern computer technology, ultrasonic testing equipment has been developed from traditional analog equipment to digital testing equipment. However, the current ultrasonic detection equipment has a single excitation pulse, most of which are sharp or square pulse, and the parameters of the pulse can not be adjusted; for most portable devices, the amplitude of power supply voltage is relatively low. As a result of insufficient detection capacity, no corresponding compensation measures have been taken. Based on this, the purpose of this paper is to study and design a digital variable pulse excitation ultrasonic detection system based on field programmable gate array (FPGA), direct digital synthesis (DDS) technology and high speed A / D (A / D). In order to improve the detection ability and adaptability of ultrasonic detection system, the generation of ultrasonic excitation signal can be controlled by programmable method to meet the needs of different testing applications. The detection system adopts direct digital synthesis (DDS) technology to control the generation of ultrasonic excitation signal by programmable method, so that the detection system can flexibly set and select the waveform of the excitation signal according to different detection needs. Number of pulses and pulse width at repetition rate. At the same time, the parameters (pulse type, pulse number, pulse width) that affect the performance of the excitation signal are studied experimentally, and the effects of the parameters on the energy of the excitation signal are analyzed. Under the condition of low excitation voltage, a new idea is proposed to increase the transmission power by increasing the number of excitation pulses properly, so as to improve the detection ability and adaptability of the detection system. In this paper, the FPGA device EP2C35F672 is used as the core control unit, and the hardware circuit of the detection system is designed by modularization. The functions of ultrasonic emission receiving, program-controlled amplification, bandpass filtering, high-speed data acquisition and man-machine interaction are realized. The hardware system adopts the components with low noise, high precision and high reliability. At the same time, many measures are taken to ensure and improve the precision and anti-interference ability of the detection system. The design and simulation of excitation signal generation, timing control, logic control, data acquisition, cache and other functional modules are completed by using FPGA development software QuartusII. The validity of the software design is verified. The function of the digital ultrasonic testing system was tested by CSK-IA standard test piece in the laboratory. The results show that the multi-pulse excitation method can obtain stronger ultrasonic echo signal at lower excitation voltage and detect defects in deeper range of workpiece effectively. Under the condition of low pulse width, the single pulse excitation method has better detection effect and strong resolution for the defect with close distribution position, so it can be used to distinguish each defect well. The system realizes the basic functions of ultrasonic echo signal conditioning, high-speed data acquisition and storage. The excitation mode of variable pulse improves the adaptive and intelligent degree of the detection system, and has strong practicability and research value.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB559
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