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本文介绍了一种能沿任意波束指向全程动态聚焦的数字波束合成器的设计,此合成器用于相控阵B超成像系统。回声信号的延时量分解为“指向延时”和“聚焦延时”两部分,分别用产生相控发射激励的时序逻辑电路和一个“动态聚焦延时量表”实现。通过对A/D采样时钟的控制及对A/D采样时钟、地址计数时钟和存储器写时钟的时序配合,实现了同相位数据点采样及无冗余数据的缓冲存储器。所设计的数字相控波束合成器只用廉价的高速数字电路即可实现,成本极低。实验结果验证了该方案的可行性。 相似文献
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随着声呐技术的发展,基阵发射波形也多种多样。为了适应这种多样化的需求,设计了一种可编程的多通道相控扫描信号源。该信号源采用数字信号处理器(Digital Signal Processor,DSP)和现场可编程门阵列(Field-Programmable Gate Array,FPGA)结合的方式,应用DSP计算各个波束的波形数据及其各通道的延时,应用FPGA的精确延时形成各个波束。该设计指向精度高,可生成任意信号波形,任意配置波束组合,可下载并存储预成波形,对波形加窗函数,可实时对延时进行补偿和校准,并能够多个信号源协同工作。在实际应用中得到了成功验证,具有很大的改进潜力和广阔的应用前景。 相似文献
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在利用声学信号分析法对滚动轴承进行故障诊断时,环境噪声或其它设备噪声会严重影响目标声信号的提取并降低诊断精度。针对这一问题,提出一种用于故障特征增强的谱峭度-波束形成方法。该方法首先利用快速谱峭度算法确定最优滤波频带,然后根据确定的频带,利用2 阶锥规划方法设计恒定束宽波束形成器并提取目标频带信号,最后对提取的带限信号进行包络解调得到轴承故障特征频率。实验结果表明,该方法能够在强干扰环境下有效提取滚动轴承故障特征,并且相较于传统的延时求和波束形成器具有更好的效果。 相似文献
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介绍了超声波油位测量的原理、电路及测控程序。油位测量计以集成锁相环解码器LM567作为超声波检测元件,以89C2051单片机作为主控元件,可用干电池供电。用超声波测量油位具有非接触、可测低温介质、无机械运动部件、寿命长等优点;以LM567作为超声波检测元件降低了系统的价格,提高超声波捕捉能力;采用单片机控制超声发射与接收,并经温度补偿后计算出油位,使检测具有高智能性。对由于超声声速变化及LM567输出延时引起测量误差的原因作了详细的分析,并提出了提高调整波速精度及调整输出延时的措施。 相似文献
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本文论述了一种提高B超图像质量的新途径。文中介绍了1/2间距波束扫描,电子多级聚焦,接收可变孔径控制等几种操作原理。在此基础上提出了高密集型用56阵元发射55阵元接收的探头新方案设想。 相似文献
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为了研究孔内分段延时起爆技术中延时时间对掏槽抛掷效果以及对岩石毁伤作用的影响,在LS-DYNA显式动力分析平台内运用SPH-FEM耦合法建立孔内分段延时爆破的三维数据模型,通过对比分析了在掏槽爆破过程中的孔内分段延时起爆下爆破产物抛掷过程,耦合效果以及掏槽演化效果,观察了爆破岩体所受到的破坏及其特征。掏槽爆破模型结果表明:在平行掏槽孔内进行分段装药时,单段药柱承载的预爆岩体减少,前端装药可为后端装药提供新的自由面,减小了掏槽爆破中岩石的挟制作用。在延时起爆时,前端装药抛掷岩石的主体脱离预爆岩体的时间约为12 ms。后端装药的延时起爆相较多段装药同时起爆显著降低了外层岩体的最大抛掷速度,有效减小了抛掷距离。 相似文献
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由于水声环境的复杂性,阵列的噪声分布可能是非一致性的。当阵元噪声功率各不相同时,阵列协方差矩阵特征分解得到的特征子空间与真实目标的特征子空间之间存在误差,导致特征子空间波束形成算法的性能衰减。文章提出了一种新的非一致性噪声条件下特征子空间的估计方法,将阵列协方差矩阵对角线置0,进行特征分解估计的特征子空间将不受阵元噪声非一致性的影响。将该方法应用到特征空间波束形成算法,提高了非一致性噪声条件下特征空间波束形成算法的方位分辨能力。仿真和实验结果验证了所提方法的可行性和有效性。 相似文献
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Computational model considerations of defect detection in pipes with bends using focused guided wave
This paper investigates the propagation of guided ultrasonic wave in pipes with bends using finite element simulation. The defect detectability in pipes with bends, using time delay focusing and synthetic focusing by common source method (CSM) are studied. Results show that the time delay focusing technique improves the confidence in detecting a small defect (3.8% cross-sectional area) beyond the bend, but it is unable to detect defects close to other features like welds or bends. Meanwhile, CSM is able to improve defect detection beyond and close to welding and bends. However, a reference image of a defect-free pipe is needed to detect defects near welds. 相似文献
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根据单波束超声波测距原理,向模拟海底钴结壳微地形的水池表面发射超声波,应用自适应滤波方法可以估计超声回波信号的时延,使最小均方误差(LMS)后的回波信号与参考信号之间方差达到最小值,此刻的延时量就是渡越时间t,从而求出探头与目标之间的距离.通过计算机仿真和试验结果表明,将最小均方误差自适应时延法应用于海底微地形高程数据的测量,获得测距精度高,能够适用于海底微地形的探测. 相似文献
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Pinton GF Trahey GE 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2006,53(11):2026-2035
Delay estimation is used in ultrasonic imaging to estimate blood flow, determine phase aberration corrections, and to calculate elastographic images. Several algorithms have been developed to determine these delays. The accuracy of these methods depends in differing ways on noise, bandwidth, and delay range. In most cases relevant to delay estimation in ultrasonics, a subsample estimate of the delay is required. We introduce two new delay algorithms that use cubic polynomial splines to continuously represent the delay. These algorithms are compared to conventional delay estimators, such as normalized cross correlation and autocorrelation, and to another spline-based method. We present simulations that compare the algorithms' performance for varying amounts of noise, delay, and bandwidth. The proposed algorithms have better performance, in terms of bias and jitter, in a realistic ultrasonic imaging environment. The computational requirements of the new algorithms also are considered. 相似文献
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Normal ultrasonic transducers of 0.5, 1, and 2 MHz are modified using delay lines which are made of Quartz. Such modification is to ameliorate the capability of the transducer to investigate Gd-doped ZnO thin films whose thickness is too thin. The normal transducers cannot test materials that have too thin thickness due to the near fields of these transducers. The near field is considered as blind area of the transducer. Therefore, the specimen under test must have thickness bigger than the near field of the used transducer, or instead delay lines can be used. Samples of Gd-doped ZnO thin films are prepared using sol gel technique. The ultrasonic pulse echo method is used at room temperature. Flaws are found in different prepared specimens. Results show that such delay lines are suitable to ameliorate the ultrasonic transducer to test Gd-doped ZnO thin films. 相似文献
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在用超声脉冲回波法检测金属-非金属粘接结构的质量以及测量非金属层厚度时,需要提取出各界面回波间的延迟时间作为特征值.当非金属层较薄时,各回波信号间会产生严重混叠,难以准确获得时延估值.提出了一种多界面粘接结构的高分辨率时延估计方法,综合利用了维纳滤波解卷积技术和最大熵谱估计方法,从混叠信号中得到精确的时延估值,很好地解决了特征值提取困难的问题,并用模拟信号和实验信号验证了该方法. 相似文献
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针对应用常规超声波方法测量极小管径(5 mm及以下)中流体速度的精度较低问题,文章应用相关函数法精确测量时延,降低噪声对测量结果的影响,提高了极小管径中流体速度的测量精度。首先,利用COMSOL Multiphysics有限元仿真软件建立管道传输模型,然后将被顺、逆水流影响后的超声波波形数据分别导入Matlab软件,用插值法处理后做相关计算,得到较为精确的时延,最后计算极小管径管道的流速。结果显示:相关函数法处理插值后的仿真数据可以得到较为精确的时延,对噪声具有一定的抑制能力。使用插值处理数据时,插值点越多即插值点间隔时间越小,测量精度越高,但是插值间隔太小会导致抗干扰能力降低。 相似文献
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Jason Wu Chan W.K. Thomas G. 《IEEE transactions on instrumentation and measurement》2001,50(1):163-168
We describe a rapid and accurate method to measure robot-to-robot separations and headings. The method, which uses narrow bandwidth signals that are well suited for ultrasonic transducers and for dispersive acoustic environments, detects the difference in phase delay of an optical and an ultrasonic signal. A prototype system based on microcontrollers for signal generation and phase delay measurement determined the location of another robot with sub-centimeter accuracy over a 2.5 m range with a 53 ms measurement time. We also describe simple modifications that can be made to increase the range without loss of accuracy and to coordinate measurements among many robots 相似文献
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超声相控阵检测技术是近年发展起来的一种先进的无损探伤方法,阵元间的延时分辨率是决定超声相控阵检测系统性能的关键因素,通过研究延时分辨率对相控阵检测效果的影响,可以得到延时分辨率和相关性能参数之间的对应关系,从而提高超声相控阵系统的检测性能。 相似文献