發(fā)布時間：2018-04-02 05:18

  本文選題：超聲相控陣　切入點：動態(tài)聚焦　出處：《西南交通大學(xué)》2014年碩士論文

【摘要】：超聲相控陣通過控制相控陣探頭的延遲時間來實現(xiàn)聲束偏轉(zhuǎn)、聚焦,從而實現(xiàn)對工件進(jìn)行快速高效的檢測。超聲相控陣系統(tǒng)中的關(guān)鍵技術(shù)是指通過對發(fā)射和接收聲束的時間和空間的有效控制,來獲得高質(zhì)量的聲束和聲場。相控陣數(shù)字技術(shù)有相位延遲技術(shù)、動態(tài)聚焦技術(shù)、動態(tài)變跡技術(shù)、動態(tài)孔徑技術(shù)和編碼發(fā)射技術(shù)等研究方向,其中動態(tài)聚焦技術(shù)是比較重要的一項。動態(tài)聚焦技術(shù)能夠提高焦點的焦區(qū)深度,減小焦點寬度,從而提高聲束的一致性和空間分辨率,為缺陷的檢測提供了更為可靠的依據(jù)。 本文重點研究了超聲相控陣聚焦技術(shù)的原理以及影響相控陣聚焦精度和分辨率的因素,提出了改善常規(guī)聚焦聲束分辨率的方法和相控陣動態(tài)聚焦壓縮存儲算法,驗證了動態(tài)聚焦技術(shù)在提高空間分辨率和成像一致性上的優(yōu)越性。 本文進(jìn)行了以下方面的研究： 1、論述了超聲相控陣檢測相關(guān)原理,如換能器的聲場輻射原理、相控陣進(jìn)行無損檢測時的聲束控制原理�；陉嚵袚Q能器的輻射原理對一維相控陣換能器的聲場建模,并系統(tǒng)的研究了換能器參數(shù)對聚焦聲束的影響,通過對不同的陣元數(shù)、陣元間距等的聚焦聲束的特性進(jìn)行對比,建立了提高超聲相控陣動態(tài)聚焦成像質(zhì)量的參數(shù)選取依據(jù)。 2、討論了延時精度對聚焦效果的影響,通過分析可知,在換能器陣列的參數(shù)已定的前提下,延時精度是影響動態(tài)聚焦聲束的重要因素。對缺陷進(jìn)行了仿真實驗,通過實驗可知,動態(tài)聚焦對成像質(zhì)量有大幅度改善。 3、提出了一種基于超聲相控陣聚焦延時參數(shù)的壓縮存儲方式。這種方法分三步：第一,將聚焦延時參數(shù)換算成相鄰陣元之間的相對延時參數(shù),然后取量化值；第二,分別存儲相對延時參數(shù)的初始值和延時值發(fā)生變化的位置,以此完成了壓縮存儲；第三,在實現(xiàn)動態(tài)聚焦的過程中,將壓縮存儲的延時量進(jìn)行實時解壓,并將生成的延時參數(shù)傳給換能器。結(jié)果驗證：此方法可再保證聚焦聲束質(zhì)量的前提下大大減小延時參數(shù)所占內(nèi)存。 4、基于FPGA設(shè)計了超聲相控陣高精度發(fā)射模塊,本文通過PLL(鎖相環(huán))的倍頻和移相技術(shù)代替了外部的延遲線,從而使電路結(jié)構(gòu)得到簡化,使粗延時和細(xì)延時的實現(xiàn)在一塊電路板上完成,在提高延時精度的前提下,解決了板間不同步的問題。
[Abstract]:Ultrasonic phased array can realize beam deflection and focus by controlling the delay time of phased array probe, so that the work piece can be detected quickly and efficiently.The key technology of ultrasonic phased array system is to obtain high quality sound beam and sound field by controlling the time and space of transmitting and receiving sound beam effectively.Phased-array digital technology includes phase delay technology, dynamic focusing technology, dynamic apodization technology, dynamic aperture technology and coded emission technology, among which dynamic focusing technology is an important one.The dynamic focusing technique can improve the focal depth and decrease the focus width, thus improving the consistency and spatial resolution of the sound beam, which provides a more reliable basis for defect detection.This paper focuses on the principle of ultrasonic phased array focusing technology and the factors that affect the accuracy and resolution of phased array focusing. A method to improve the conventional focusing sound beam resolution and a dynamic focusing compression storage algorithm for phased array are proposed.The advantages of dynamic focusing technique in improving spatial resolution and imaging consistency are verified.In this paper, the following aspects of the research:1. The related principles of ultrasonic phased array detection, such as the sound field radiation principle of transducer and the sound beam control principle of phased array nondestructive testing, are discussed.Based on the radiation principle of array transducer, the sound field of one-dimensional phased array transducer is modeled, and the influence of transducer parameters on focused sound beam is systematically studied.The parameter selection basis for improving the quality of ultrasonic phased array dynamic focusing imaging is established.2. The effect of delay precision on focusing effect is discussed. Through analysis, it is known that delay precision is an important factor affecting dynamic focusing sound beam on the premise that the parameters of transducer array have been determined.The simulation results show that dynamic focusing can improve the imaging quality greatly.3. A compression storage method based on ultrasonic phased array focusing delay parameters is proposed.This method is divided into three steps: first, the focusing delay parameters are converted into the relative delay parameters between adjacent array elements, and then the quantization values are taken; second, the initial values of the relative delay parameters and the positions where the delay values change are stored respectively.In the process of dynamic focusing, the time delay of the compressed storage is decompressed in real time, and the generated delay parameters are transmitted to the transducer.The results show that this method can greatly reduce the memory occupied by delay parameters on the premise of focusing sound beam quality.4. Based on FPGA, the high precision transmission module of ultrasonic phased array is designed. In this paper, the frequency doubling and phase shifting technology of PLL (PLL) are used to replace the external delay lines, so the circuit structure is simplified.The realization of coarse delay and fine delay is completed on a single circuit board, and the problem of non-synchronization between boards is solved on the premise of improving delay precision.
【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】：2014
【分類號】：TB553

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本文編號：1698953