【摘要】：超聲波檢測是鐵路機車車輛零部件及鋼軌無損檢測的主要技術(shù)手段。國內(nèi)外許多鐵路部門都十分重視研發(fā)用于機車車輛零部件及鋼軌無損檢測的超聲波檢測設(shè)備。隨著數(shù)字電子技術(shù)和現(xiàn)代計算機技術(shù)的發(fā)展,超聲波檢測設(shè)備由傳統(tǒng)的模擬式設(shè)備向數(shù)字式檢測設(shè)備發(fā)展。但是現(xiàn)今存在的超聲波檢測設(shè)備的激勵脈沖比較單一,多為尖脈沖或方波脈沖,且脈沖的多個參數(shù)無法調(diào)節(jié)；對于大多數(shù)便攜式設(shè)備,電源電壓幅值較低,致使檢測能力不夠的情況,也沒有采取相應(yīng)補償措施�；诖�,本論文旨在研究和設(shè)計以現(xiàn)場可編程門陣列(FPGA)為核心、直接數(shù)字合成(DDS)技術(shù)為技術(shù)手段、輔以高速A/D的數(shù)字式可變脈沖激勵超聲波檢測系統(tǒng),通過可編程方式控制超聲波激勵信號的產(chǎn)生,以提高超聲檢測系統(tǒng)的檢測能力和適應(yīng)性,滿足不同檢測應(yīng)用的需求。本檢測系統(tǒng)采用直接數(shù)字合成(DDS)技術(shù),通過可編程方式控制超聲波激勵信號的產(chǎn)生,使檢測系統(tǒng)能針對不同檢測需要,靈活設(shè)置和選擇激勵信號的波形、重復(fù)頻率脈沖個數(shù)和脈沖寬度。同時,對影響激勵信號性能的參數(shù)(脈沖類型、脈沖個數(shù)、脈沖寬度)進行了實驗性研究,分析了各參數(shù)對激勵信號能量的影響。提出在低激勵電壓條件下,以適當增加激勵脈沖個數(shù)的方式來提高發(fā)射功率,從而提高檢測系統(tǒng)的檢測能力和適應(yīng)性的新思想。論文以FPGA器件EP2C35F672為核心控制單元,采用模塊化思想完成了檢測系統(tǒng)的硬件電路設(shè)計,實現(xiàn)了超聲波發(fā)射接收、程控放大、帶通濾波、高速數(shù)據(jù)采集及人機交互等功能。硬件系統(tǒng)均采用噪聲低、精度高和可靠性高的元器件,同時在設(shè)計制作時還采取了多種措施來保障和提高檢測系統(tǒng)的精度和抗干擾能力。采用FPGA開發(fā)軟件QuartusII完成了激勵信號產(chǎn)生、時序控制、邏輯控制、數(shù)據(jù)采集、緩存等功能模塊的設(shè)計與仿真,對軟件設(shè)計的有效性進行了驗證。在實驗室采用CSK-IA標準試塊對所設(shè)計的數(shù)字式超聲波檢測系統(tǒng)進行了功能測試。結(jié)果表明,多脈沖激勵的方式能夠在較低的激勵電壓下,獲得更強的超聲回波信號,實現(xiàn)工件內(nèi)部更深范圍內(nèi)缺陷的有效檢出。單脈沖激勵方式在較低的脈沖寬度條件下,對分布位置接近的缺陷檢測效果較好、分辨力強,可以很好的分辨各缺陷。本檢測系統(tǒng)實現(xiàn)了超聲回波信號調(diào)理、高速數(shù)據(jù)采集及存儲的基本功能：可變脈沖的激勵方式提高了檢測系統(tǒng)的自適應(yīng)及智能化程度,具有極強的實用性和研究價值。
[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.
【學(xué)位授予單位】：西南交通大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TB559

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本文編號：2276277